Ramblings about Airborne Power supply design and testing

Over the last few years the RF design work in my company has dried up and I have been frequently assigned to power supply testing (and some design) pe r MIL-STD-704 and DO-160.

Here goes..... Item 1.

Q. What do all of these test boil down to? A. Aside from working over the specified input voltages and conditions ("no rmal operation" - which have a few subtleties) the important thing is that if 28V (typical nominal voltage for my category of equipment) is present on the input the box better be working. It is surprising how difficult that simple requirement is to achieve. The testing regiment requires the unit t o be put through many types of over/under voltage tests that will take the box down and then the requirement is that the unit re-powers up without use r intervention and works correctly. This is not a trivial requirement. Mu ch of the testing really revolves around the standard's notion that this is not a trivial requirement.

---As an aside , one aircraft manufacturer requires additional tests above and beyond those in DO-160. In one case they require 8 waveforms that impo se glitches on the startup voltage when powering up. Sure enough, we ran t hese waveforms and one of their sequences locked our unit up (power was app lied to the terminals and the unit was latched up and required user interve ntion to power it off and back on to get it to work).

Many (most) of our products require a write to flash memory on power down.. ...oh boy , this requires a lot of attention to get it right.

Item 2.... Just run the waveforms.....OK, I have had to work real hard, at times, to educate my management that most of the time I find a problem it i s in the setting up of the required waveforms. Say I have an undervoltage requirement of 12 Volts and as I am setting it up I apply 11 volts and the unit locks up. The first thing a manager tries to do (until properly educa ted....fortunately my mangers do try to do the right thing....most of the t ime) is to ask if the unit works with the specified waveform and I have to answer yes.....but.....The real purpose of the test is to make you look at the unit 100 different ways to Sunday to see if the unit latches up and par t of the process is the setup variations that will frequently be where the sweet (sour) spot is. So I have to go back and remind them that if I can ha ve 28V appllied to the box and it is latched up it really does not matter w hat I did to the unit before ---the box not adequate for an aircraft. (of course this whatever you do are within reasonable guidelines....undervoltag es, short duration overvoltages and some ripple on the input voltage). Whe n a manager tries to tell me to just run the waveforms I ask him if we can have this discussion with the customer to get clarification.....99% of the time that forces the required (and painful) design changes.

Item 3. Power input is a big deal to aircaft manufacturers. If you think MIL-STD-704/DO-160 is rigorous you should see what one well known aircraft manufacturer in France requires in addition to DO-160. It takes weeks to r un the tests.....They do not want a box to latch up on their aircraft

Item 4. Normal operation.... These are the voltage variations that are app lied that the unit is expected to work through. The aircraft manufacturers HATE HATE HATE latchups, but they also do not like the unit temporarily sh utting off when it should not shut off. These normal operation requirements revolve around3 basic things 1. the unit will stay powered up for 200 ms ( this can vary) when power drops below a specified voltage (hold-up cap requ ired) 2. The unit will stay powered up when over voltages are less than 200 ms 3. The unit will operate through various audio frequencies imposed on t op of the DC voltage. 4. The unit will operate from typically 16or18V to ap proximately 29-33 volts (each unit will have these nailed down exactly in a spec)

Item 5. All the other stresses are abnormal conditions and they should not cause the unit to latch up (per above) and also not damage the unit (OK th ats obvious, but it is explicitly stated and required).

Item 6. Ideal diodes, they are not so ideal. I have seen designs where an Ideal diode (smart FET) is used instead of a schottky diode on the input. Yeah they work for negative voltages....but About those Audio frequencies imposed on the DC lines..... , they walk right through the ideal diode. I am of the persuasion to use a schottky diode with a large capacitor after it. This will not allow internal resonances to develop which can cause man y amps of current to circulate through the input circuitry. Take the 0.5V hit on efficiency. The real diode is so much nicer (do note I am coming at this for units that are 30W or less, usually less).

Item 7. Application of transients. MIL-STD-704 typically requires 5 appli cations of a particular interrupt (for instance) waveform. I insist on doi ng each one manually and slowly. Apply and observe before the next applica tion of the transient. I have seen where people try to automate these tran sient applications and wind up making a burst of 5. I think this breaks th e spirit of what is expected. I have seen the automatic test blow through t hem so fast that you cannot even tell what happened. I insist on manual ap plication of transient waveforms.

Item 8 Some things can be automated. For instance , the slow sweep and dwe ll of audio frequncy ripple is OK if you are still able to properly monitor the equipment.

Item 9. In MIL-STD-704 people get confused because the first battery of tes ts are not about how the unit operates with voltage corruptions, but rather it is an assessment of how your unit might affect the power bus. For low power equipment always fight for these things to be characterized but not s pecified. EVERY TIME I test any of these items to a spec it fails....Espec ially inrush current. Just characterize it!

Item 10. Inrush current. On low power units fight, FIGHT, FIGHT against a hard spec. It will fail. Fight to characterize it. Low power stuff is n ot going to take down the aircraft power bus and your internal capacitors h ave to get charged up and yes, your EMI caps theoretically take infinite cu rrent for short durations to charge up. When you design around inrush you start to take away internal capacitance that you really want. The aircraft has to tranfer energy into your unit on power up. I think the aircraft ma nufacturers get that but the designers see a spec as a challenge and try to meet it (at the expense of inadequate internal capacitance or being in the crappy position of telling your management that you failed at test time).. .Actually, the customer will probably give you relief on it (not on anythin g else though)so fight up front to avoid the headaches.

Item 11.....OK I guess I am done for now...Bye

Reply to
blocher
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I have been frequently assigned to power supply testing (and some design) per MIL-STD-704 and DO-160.

normal operation" - which have a few subtleties) the important thing is tha t if 28V (typical nominal voltage for my category of equipment) is present on the input the box better be working. It is surprising how difficult tha t simple requirement is to achieve. The testing regiment requires the unit to be put through many types of over/under voltage tests that will take th e box down and then the requirement is that the unit re-powers up without u ser intervention and works correctly. This is not a trivial requirement. Much of the testing really revolves around the standard's notion that this is not a trivial requirement.

e and beyond those in DO-160. In one case they require 8 waveforms that im pose glitches on the startup voltage when powering up. Sure enough, we ran these waveforms and one of their sequences locked our unit up (power was a pplied to the terminals and the unit was latched up and required user inter vention to power it off and back on to get it to work).

.....oh boy , this requires a lot of attention to get it right.

t times, to educate my management that most of the time I find a problem it is in the setting up of the required waveforms. Say I have an undervoltag e requirement of 12 Volts and as I am setting it up I apply 11 volts and th e unit locks up. The first thing a manager tries to do (until properly edu cated....fortunately my mangers do try to do the right thing....most of the time) is to ask if the unit works with the specified waveform and I have t o answer yes.....but.....The real purpose of the test is to make you look a t the unit 100 different ways to Sunday to see if the unit latches up and p art of the process is the setup variations that will frequently be where th e sweet (sour) spot is. So I have to go back and remind them that if I can have 28V appllied to the box and it is latched up it really does not matter what I did to the unit before ---the box not adequate for an aircraft. (o f course this whatever you do are within reasonable guidelines....undervolt ages, short duration overvoltages and some ripple on the input voltage). W hen a manager tries to tell me to just run the waveforms I ask him if we ca n have this discussion with the customer to get clarification.....99% of th e time that forces the required (and painful) design changes.

k MIL-STD-704/DO-160 is rigorous you should see what one well known aircraf t manufacturer in France requires in addition to DO-160. It takes weeks to run the tests.....They do not want a box to latch up on their aircraft

pplied that the unit is expected to work through. The aircraft manufacture rs HATE HATE HATE latchups, but they also do not like the unit temporarily shutting off when it should not shut off. These normal operation requiremen ts revolve around3 basic things 1. the unit will stay powered up for 200 ms (this can vary) when power drops below a specified voltage (hold-up cap re quired) 2. The unit will stay powered up when over voltages are less than 2

00 ms 3. The unit will operate through various audio frequencies imposed on top of the DC voltage. 4. The unit will operate from typically 16or18V to approximately 29-33 volts (each unit will have these nailed down exactly in a spec)

ot cause the unit to latch up (per above) and also not damage the unit (OK thats obvious, but it is explicitly stated and required).

n Ideal diode (smart FET) is used instead of a schottky diode on the input. Yeah they work for negative voltages....but About those Audio frequencie s imposed on the DC lines..... , they walk right through the ideal diode. I am of the persuasion to use a schottky diode with a large capacitor afte r it. This will not allow internal resonances to develop which can cause m any amps of current to circulate through the input circuitry. Take the 0.5 V hit on efficiency. The real diode is so much nicer (do note I am coming at this for units that are 30W or less, usually less).

lications of a particular interrupt (for instance) waveform. I insist on d oing each one manually and slowly. Apply and observe before the next appli cation of the transient. I have seen where people try to automate these tr ansient applications and wind up making a burst of 5. I think this breaks the spirit of what is expected. I have seen the automatic test blow through them so fast that you cannot even tell what happened. I insist on manual application of transient waveforms.

well of audio frequncy ripple is OK if you are still able to properly monit or the equipment.

ests are not about how the unit operates with voltage corruptions, but rath er it is an assessment of how your unit might affect the power bus. For lo w power equipment always fight for these things to be characterized but not specified. EVERY TIME I test any of these items to a spec it fails....Esp ecially inrush current. Just characterize it!

a hard spec. It will fail. Fight to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacitors have to get charged up and yes, your EMI caps theoretically take infinite current for short durations to charge up. When you design around inrush yo u start to take away internal capacitance that you really want. The aircra ft has to tranfer energy into your unit on power up. I think the aircraft manufacturers get that but the designers see a spec as a challenge and try to meet it (at the expense of inadequate internal capacitance or being in t he crappy position of telling your management that you failed at test time) ...Actually, the customer will probably give you relief on it (not on anyth ing else though)so fight up front to avoid the headaches.

Item 11. I really like power supplies to be on or off, no wierd states at low voltage especially. Again, this is not so easy. I really like a lot (

2 volts) of hysteresis at low voltages to force the unit to either be on or off. A flyback transformer on the input can really act squirrely right a t turn on.
Reply to
blocher

I have been frequently assigned to power supply testing (and some design) per MIL-STD-704 and DO-160.

normal operation" - which have a few subtleties) the important thing is tha t if 28V (typical nominal voltage for my category of equipment) is present on the input the box better be working. It is surprising how difficult tha t simple requirement is to achieve. The testing regiment requires the unit to be put through many types of over/under voltage tests that will take th e box down and then the requirement is that the unit re-powers up without u ser intervention and works correctly. This is not a trivial requirement. Much of the testing really revolves around the standard's notion that this is not a trivial requirement.

e and beyond those in DO-160. In one case they require 8 waveforms that im pose glitches on the startup voltage when powering up. Sure enough, we ran these waveforms and one of their sequences locked our unit up (power was a pplied to the terminals and the unit was latched up and required user inter vention to power it off and back on to get it to work).

.....oh boy , this requires a lot of attention to get it right.

t times, to educate my management that most of the time I find a problem it is in the setting up of the required waveforms. Say I have an undervoltag e requirement of 12 Volts and as I am setting it up I apply 11 volts and th e unit locks up. The first thing a manager tries to do (until properly edu cated....fortunately my mangers do try to do the right thing....most of the time) is to ask if the unit works with the specified waveform and I have t o answer yes.....but.....The real purpose of the test is to make you look a t the unit 100 different ways to Sunday to see if the unit latches up and p art of the process is the setup variations that will frequently be where th e sweet (sour) spot is. So I have to go back and remind them that if I can have 28V appllied to the box and it is latched up it really does not matter what I did to the unit before ---the box not adequate for an aircraft. (o f course this whatever you do are within reasonable guidelines....undervolt ages, short duration overvoltages and some ripple on the input voltage). W hen a manager tries to tell me to just run the waveforms I ask him if we ca n have this discussion with the customer to get clarification.....99% of th e time that forces the required (and painful) design changes.

k MIL-STD-704/DO-160 is rigorous you should see what one well known aircraf t manufacturer in France requires in addition to DO-160. It takes weeks to run the tests.....They do not want a box to latch up on their aircraft

pplied that the unit is expected to work through. The aircraft manufacture rs HATE HATE HATE latchups, but they also do not like the unit temporarily shutting off when it should not shut off. These normal operation requiremen ts revolve around3 basic things 1. the unit will stay powered up for 200 ms (this can vary) when power drops below a specified voltage (hold-up cap re quired) 2. The unit will stay powered up when over voltages are less than 2

00 ms 3. The unit will operate through various audio frequencies imposed on top of the DC voltage. 4. The unit will operate from typically 16or18V to approximately 29-33 volts (each unit will have these nailed down exactly in a spec)

ot cause the unit to latch up (per above) and also not damage the unit (OK thats obvious, but it is explicitly stated and required).

n Ideal diode (smart FET) is used instead of a schottky diode on the input. Yeah they work for negative voltages....but About those Audio frequencie s imposed on the DC lines..... , they walk right through the ideal diode. I am of the persuasion to use a schottky diode with a large capacitor afte r it. This will not allow internal resonances to develop which can cause m any amps of current to circulate through the input circuitry. Take the 0.5 V hit on efficiency. The real diode is so much nicer (do note I am coming at this for units that are 30W or less, usually less).

lications of a particular interrupt (for instance) waveform. I insist on d oing each one manually and slowly. Apply and observe before the next appli cation of the transient. I have seen where people try to automate these tr ansient applications and wind up making a burst of 5. I think this breaks the spirit of what is expected. I have seen the automatic test blow through them so fast that you cannot even tell what happened. I insist on manual application of transient waveforms.

well of audio frequncy ripple is OK if you are still able to properly monit or the equipment.

ests are not about how the unit operates with voltage corruptions, but rath er it is an assessment of how your unit might affect the power bus. For lo w power equipment always fight for these things to be characterized but not specified. EVERY TIME I test any of these items to a spec it fails....Esp ecially inrush current. Just characterize it!

a hard spec. It will fail. Fight to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacitors have to get charged up and yes, your EMI caps theoretically take infinite current for short durations to charge up. When you design around inrush yo u start to take away internal capacitance that you really want. The aircra ft has to tranfer energy into your unit on power up. I think the aircraft manufacturers get that but the designers see a spec as a challenge and try to meet it (at the expense of inadequate internal capacitance or being in t he crappy position of telling your management that you failed at test time) ...Actually, the customer will probably give you relief on it (not on anyth ing else though)so fight up front to avoid the headaches.

Item 12. Failsafes....In avionics a broken box that gets pulled and sent b ack to us is better than a not-broken box that gets sent back to us. The d isaster is the box getting pulled, not the box being broken, per say. If y ou put in failsafes that mask a failure in order to protect the unit from d amage, this may actually cause more harm than good.

Reply to
blocher

I have been frequently assigned to power supply testing (and some design) per MIL-STD-704 and DO-160.

normal operation" - which have a few subtleties) the important thing is tha t if 28V (typical nominal voltage for my category of equipment) is present on the input the box better be working. It is surprising how difficult tha t simple requirement is to achieve. The testing regiment requires the unit to be put through many types of over/under voltage tests that will take th e box down and then the requirement is that the unit re-powers up without u ser intervention and works correctly. This is not a trivial requirement. Much of the testing really revolves around the standard's notion that this is not a trivial requirement.

e and beyond those in DO-160. In one case they require 8 waveforms that im pose glitches on the startup voltage when powering up. Sure enough, we ran these waveforms and one of their sequences locked our unit up (power was a pplied to the terminals and the unit was latched up and required user inter vention to power it off and back on to get it to work).

.....oh boy , this requires a lot of attention to get it right.

t times, to educate my management that most of the time I find a problem it is in the setting up of the required waveforms. Say I have an undervoltag e requirement of 12 Volts and as I am setting it up I apply 11 volts and th e unit locks up. The first thing a manager tries to do (until properly edu cated....fortunately my mangers do try to do the right thing....most of the time) is to ask if the unit works with the specified waveform and I have t o answer yes.....but.....The real purpose of the test is to make you look a t the unit 100 different ways to Sunday to see if the unit latches up and p art of the process is the setup variations that will frequently be where th e sweet (sour) spot is. So I have to go back and remind them that if I can have 28V appllied to the box and it is latched up it really does not matter what I did to the unit before ---the box not adequate for an aircraft. (o f course this whatever you do are within reasonable guidelines....undervolt ages, short duration overvoltages and some ripple on the input voltage). W hen a manager tries to tell me to just run the waveforms I ask him if we ca n have this discussion with the customer to get clarification.....99% of th e time that forces the required (and painful) design changes.

k MIL-STD-704/DO-160 is rigorous you should see what one well known aircraf t manufacturer in France requires in addition to DO-160. It takes weeks to run the tests.....They do not want a box to latch up on their aircraft

pplied that the unit is expected to work through. The aircraft manufacture rs HATE HATE HATE latchups, but they also do not like the unit temporarily shutting off when it should not shut off. These normal operation requiremen ts revolve around3 basic things 1. the unit will stay powered up for 200 ms (this can vary) when power drops below a specified voltage (hold-up cap re quired) 2. The unit will stay powered up when over voltages are less than 2

00 ms 3. The unit will operate through various audio frequencies imposed on top of the DC voltage. 4. The unit will operate from typically 16or18V to approximately 29-33 volts (each unit will have these nailed down exactly in a spec)

ot cause the unit to latch up (per above) and also not damage the unit (OK thats obvious, but it is explicitly stated and required).

n Ideal diode (smart FET) is used instead of a schottky diode on the input. Yeah they work for negative voltages....but About those Audio frequencie s imposed on the DC lines..... , they walk right through the ideal diode. I am of the persuasion to use a schottky diode with a large capacitor afte r it. This will not allow internal resonances to develop which can cause m any amps of current to circulate through the input circuitry. Take the 0.5 V hit on efficiency. The real diode is so much nicer (do note I am coming at this for units that are 30W or less, usually less).

lications of a particular interrupt (for instance) waveform. I insist on d oing each one manually and slowly. Apply and observe before the next appli cation of the transient. I have seen where people try to automate these tr ansient applications and wind up making a burst of 5. I think this breaks the spirit of what is expected. I have seen the automatic test blow through them so fast that you cannot even tell what happened. I insist on manual application of transient waveforms.

well of audio frequncy ripple is OK if you are still able to properly monit or the equipment.

ests are not about how the unit operates with voltage corruptions, but rath er it is an assessment of how your unit might affect the power bus. For lo w power equipment always fight for these things to be characterized but not specified. EVERY TIME I test any of these items to a spec it fails....Esp ecially inrush current. Just characterize it!

a hard spec. It will fail. Fight to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacitors have to get charged up and yes, your EMI caps theoretically take infinite current for short durations to charge up. When you design around inrush yo u start to take away internal capacitance that you really want. The aircra ft has to tranfer energy into your unit on power up. I think the aircraft manufacturers get that but the designers see a spec as a challenge and try to meet it (at the expense of inadequate internal capacitance or being in t he crappy position of telling your management that you failed at test time) ...Actually, the customer will probably give you relief on it (not on anyth ing else though)so fight up front to avoid the headaches.

Item 13. Limits(specs) vs tests. There is some confusion here because typ ically the spec (say MIL-STD-704) has a specification which shows the requi rement as a limit curve. What does that mean? How do you know if you satis fy the specification because it is such a broad and all encompassing curve? Fortunately, the military provides MIL-HDBK-704 which defines specific te sts. The idea is that if you follow the testing regimen defined in MIL-HDB K-704 then you can rightfully claim that you meet the specification.

Reply to
blocher

I have been frequently assigned to power supply testing (and some design) per MIL-STD-704 and DO-160.

normal operation" - which have a few subtleties) the important thing is tha t if 28V (typical nominal voltage for my category of equipment) is present on the input the box better be working. It is surprising how difficult tha t simple requirement is to achieve. The testing regiment requires the unit to be put through many types of over/under voltage tests that will take th e box down and then the requirement is that the unit re-powers up without u ser intervention and works correctly. This is not a trivial requirement. Much of the testing really revolves around the standard's notion that this is not a trivial requirement.

e and beyond those in DO-160. In one case they require 8 waveforms that im pose glitches on the startup voltage when powering up. Sure enough, we ran these waveforms and one of their sequences locked our unit up (power was a pplied to the terminals and the unit was latched up and required user inter vention to power it off and back on to get it to work).

.....oh boy , this requires a lot of attention to get it right.

t times, to educate my management that most of the time I find a problem it is in the setting up of the required waveforms. Say I have an undervoltag e requirement of 12 Volts and as I am setting it up I apply 11 volts and th e unit locks up. The first thing a manager tries to do (until properly edu cated....fortunately my mangers do try to do the right thing....most of the time) is to ask if the unit works with the specified waveform and I have t o answer yes.....but.....The real purpose of the test is to make you look a t the unit 100 different ways to Sunday to see if the unit latches up and p art of the process is the setup variations that will frequently be where th e sweet (sour) spot is. So I have to go back and remind them that if I can have 28V appllied to the box and it is latched up it really does not matter what I did to the unit before ---the box not adequate for an aircraft. (o f course this whatever you do are within reasonable guidelines....undervolt ages, short duration overvoltages and some ripple on the input voltage). W hen a manager tries to tell me to just run the waveforms I ask him if we ca n have this discussion with the customer to get clarification.....99% of th e time that forces the required (and painful) design changes.

k MIL-STD-704/DO-160 is rigorous you should see what one well known aircraf t manufacturer in France requires in addition to DO-160. It takes weeks to run the tests.....They do not want a box to latch up on their aircraft

pplied that the unit is expected to work through. The aircraft manufacture rs HATE HATE HATE latchups, but they also do not like the unit temporarily shutting off when it should not shut off. These normal operation requiremen ts revolve around3 basic things 1. the unit will stay powered up for 200 ms (this can vary) when power drops below a specified voltage (hold-up cap re quired) 2. The unit will stay powered up when over voltages are less than 2

00 ms 3. The unit will operate through various audio frequencies imposed on top of the DC voltage. 4. The unit will operate from typically 16or18V to approximately 29-33 volts (each unit will have these nailed down exactly in a spec)

ot cause the unit to latch up (per above) and also not damage the unit (OK thats obvious, but it is explicitly stated and required).

n Ideal diode (smart FET) is used instead of a schottky diode on the input. Yeah they work for negative voltages....but About those Audio frequencie s imposed on the DC lines..... , they walk right through the ideal diode. I am of the persuasion to use a schottky diode with a large capacitor afte r it. This will not allow internal resonances to develop which can cause m any amps of current to circulate through the input circuitry. Take the 0.5 V hit on efficiency. The real diode is so much nicer (do note I am coming at this for units that are 30W or less, usually less).

lications of a particular interrupt (for instance) waveform. I insist on d oing each one manually and slowly. Apply and observe before the next appli cation of the transient. I have seen where people try to automate these tr ansient applications and wind up making a burst of 5. I think this breaks the spirit of what is expected. I have seen the automatic test blow through them so fast that you cannot even tell what happened. I insist on manual application of transient waveforms.

well of audio frequncy ripple is OK if you are still able to properly monit or the equipment.

ests are not about how the unit operates with voltage corruptions, but rath er it is an assessment of how your unit might affect the power bus. For lo w power equipment always fight for these things to be characterized but not specified. EVERY TIME I test any of these items to a spec it fails....Esp ecially inrush current. Just characterize it!

a hard spec. It will fail. Fight to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacitors have to get charged up and yes, your EMI caps theoretically take infinite current for short durations to charge up. When you design around inrush yo u start to take away internal capacitance that you really want. The aircra ft has to tranfer energy into your unit on power up. I think the aircraft manufacturers get that but the designers see a spec as a challenge and try to meet it (at the expense of inadequate internal capacitance or being in t he crappy position of telling your management that you failed at test time) ...Actually, the customer will probably give you relief on it (not on anyth ing else though)so fight up front to avoid the headaches.

Item 14. I have an old picker MRI coil driver amp. I use this in conjunct ion with an arbitrary waveform generator. This picker amp is a very high cu rrent OP-AMP that can also generate high voltages ( about 90 -100V). It is a VERY impressive thing. It has a BW of maybe 200 KHz -- although I have n ot explicitly looked at that. I one time dropped the output on a copper ta ble and the banana plug was obliterated. The picker amp could have cared l ess. You can buy the amplifier with all the waveforms built in, but I pref er to roll my own with my trusty picker amplifier. Frequently a customer wa nts a particular waveform run (The old we got burned by that once 20 years ago and never again thingy) and the generator with all the "canned waveform s" does not have it so you have to roll your own anyway. It is so much eas ier to make slight voltage tweeks to the AWG than to tweek the canned wavef orms.

Reply to
blocher

I have been frequently assigned to power supply testing (and some design) per MIL-STD-704 and DO-160.

normal operation" - which have a few subtleties) the important thing is tha t if 28V (typical nominal voltage for my category of equipment) is present on the input the box better be working. It is surprising how difficult tha t simple requirement is to achieve. The testing regiment requires the unit to be put through many types of over/under voltage tests that will take th e box down and then the requirement is that the unit re-powers up without u ser intervention and works correctly. This is not a trivial requirement. Much of the testing really revolves around the standard's notion that this is not a trivial requirement.

e and beyond those in DO-160. In one case they require 8 waveforms that im pose glitches on the startup voltage when powering up. Sure enough, we ran these waveforms and one of their sequences locked our unit up (power was a pplied to the terminals and the unit was latched up and required user inter vention to power it off and back on to get it to work).

.....oh boy , this requires a lot of attention to get it right.

t times, to educate my management that most of the time I find a problem it is in the setting up of the required waveforms. Say I have an undervoltag e requirement of 12 Volts and as I am setting it up I apply 11 volts and th e unit locks up. The first thing a manager tries to do (until properly edu cated....fortunately my mangers do try to do the right thing....most of the time) is to ask if the unit works with the specified waveform and I have t o answer yes.....but.....The real purpose of the test is to make you look a t the unit 100 different ways to Sunday to see if the unit latches up and p art of the process is the setup variations that will frequently be where th e sweet (sour) spot is. So I have to go back and remind them that if I can have 28V appllied to the box and it is latched up it really does not matter what I did to the unit before ---the box not adequate for an aircraft. (o f course this whatever you do are within reasonable guidelines....undervolt ages, short duration overvoltages and some ripple on the input voltage). W hen a manager tries to tell me to just run the waveforms I ask him if we ca n have this discussion with the customer to get clarification.....99% of th e time that forces the required (and painful) design changes.

k MIL-STD-704/DO-160 is rigorous you should see what one well known aircraf t manufacturer in France requires in addition to DO-160. It takes weeks to run the tests.....They do not want a box to latch up on their aircraft

pplied that the unit is expected to work through. The aircraft manufacture rs HATE HATE HATE latchups, but they also do not like the unit temporarily shutting off when it should not shut off. These normal operation requiremen ts revolve around3 basic things 1. the unit will stay powered up for 200 ms (this can vary) when power drops below a specified voltage (hold-up cap re quired) 2. The unit will stay powered up when over voltages are less than 2

00 ms 3. The unit will operate through various audio frequencies imposed on top of the DC voltage. 4. The unit will operate from typically 16or18V to approximately 29-33 volts (each unit will have these nailed down exactly in a spec)

ot cause the unit to latch up (per above) and also not damage the unit (OK thats obvious, but it is explicitly stated and required).

n Ideal diode (smart FET) is used instead of a schottky diode on the input. Yeah they work for negative voltages....but About those Audio frequencie s imposed on the DC lines..... , they walk right through the ideal diode. I am of the persuasion to use a schottky diode with a large capacitor afte r it. This will not allow internal resonances to develop which can cause m any amps of current to circulate through the input circuitry. Take the 0.5 V hit on efficiency. The real diode is so much nicer (do note I am coming at this for units that are 30W or less, usually less).

lications of a particular interrupt (for instance) waveform. I insist on d oing each one manually and slowly. Apply and observe before the next appli cation of the transient. I have seen where people try to automate these tr ansient applications and wind up making a burst of 5. I think this breaks the spirit of what is expected. I have seen the automatic test blow through them so fast that you cannot even tell what happened. I insist on manual application of transient waveforms.

well of audio frequncy ripple is OK if you are still able to properly monit or the equipment.

ests are not about how the unit operates with voltage corruptions, but rath er it is an assessment of how your unit might affect the power bus. For lo w power equipment always fight for these things to be characterized but not specified. EVERY TIME I test any of these items to a spec it fails....Esp ecially inrush current. Just characterize it!

a hard spec. It will fail. Fight to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacitors have to get charged up and yes, your EMI caps theoretically take infinite current for short durations to charge up. When you design around inrush yo u start to take away internal capacitance that you really want. The aircra ft has to tranfer energy into your unit on power up. I think the aircraft manufacturers get that but the designers see a spec as a challenge and try to meet it (at the expense of inadequate internal capacitance or being in t he crappy position of telling your management that you failed at test time) ...Actually, the customer will probably give you relief on it (not on anyth ing else though)so fight up front to avoid the headaches.

Item 15...400Vac testing. These standards define tests for 28V systems, 40

0Hz 115 single phase, 400V 115 3phase and 270 V. I have been exploring the 400Hz single phase. This typically requires going to a dedicated lab to run these test (frequency and amplitude variations are simultaneously requi red). I am testing low power equipment so I am currently running my trusty picker with a step up transformer to se if I can generate many (if not all ) of the 400Hz required waveforms. So far so good. I think I can do most of the waveforms in house for confidence testing.
Reply to
blocher

I have been frequently assigned to power supply testing (and some design) per MIL-STD-704 and DO-160.

normal operation" - which have a few subtleties) the important thing is tha t if 28V (typical nominal voltage for my category of equipment) is present on the input the box better be working. It is surprising how difficult tha t simple requirement is to achieve. The testing regiment requires the unit to be put through many types of over/under voltage tests that will take th e box down and then the requirement is that the unit re-powers up without u ser intervention and works correctly. This is not a trivial requirement. Much of the testing really revolves around the standard's notion that this is not a trivial requirement.

e and beyond those in DO-160. In one case they require 8 waveforms that im pose glitches on the startup voltage when powering up. Sure enough, we ran these waveforms and one of their sequences locked our unit up (power was a pplied to the terminals and the unit was latched up and required user inter vention to power it off and back on to get it to work).

.....oh boy , this requires a lot of attention to get it right.

t times, to educate my management that most of the time I find a problem it is in the setting up of the required waveforms. Say I have an undervoltag e requirement of 12 Volts and as I am setting it up I apply 11 volts and th e unit locks up. The first thing a manager tries to do (until properly edu cated....fortunately my mangers do try to do the right thing....most of the time) is to ask if the unit works with the specified waveform and I have t o answer yes.....but.....The real purpose of the test is to make you look a t the unit 100 different ways to Sunday to see if the unit latches up and p art of the process is the setup variations that will frequently be where th e sweet (sour) spot is. So I have to go back and remind them that if I can have 28V appllied to the box and it is latched up it really does not matter what I did to the unit before ---the box not adequate for an aircraft. (o f course this whatever you do are within reasonable guidelines....undervolt ages, short duration overvoltages and some ripple on the input voltage). W hen a manager tries to tell me to just run the waveforms I ask him if we ca n have this discussion with the customer to get clarification.....99% of th e time that forces the required (and painful) design changes.

k MIL-STD-704/DO-160 is rigorous you should see what one well known aircraf t manufacturer in France requires in addition to DO-160. It takes weeks to run the tests.....They do not want a box to latch up on their aircraft

pplied that the unit is expected to work through. The aircraft manufacture rs HATE HATE HATE latchups, but they also do not like the unit temporarily shutting off when it should not shut off. These normal operation requiremen ts revolve around3 basic things 1. the unit will stay powered up for 200 ms (this can vary) when power drops below a specified voltage (hold-up cap re quired) 2. The unit will stay powered up when over voltages are less than 2

00 ms 3. The unit will operate through various audio frequencies imposed on top of the DC voltage. 4. The unit will operate from typically 16or18V to approximately 29-33 volts (each unit will have these nailed down exactly in a spec)

ot cause the unit to latch up (per above) and also not damage the unit (OK thats obvious, but it is explicitly stated and required).

n Ideal diode (smart FET) is used instead of a schottky diode on the input. Yeah they work for negative voltages....but About those Audio frequencie s imposed on the DC lines..... , they walk right through the ideal diode. I am of the persuasion to use a schottky diode with a large capacitor afte r it. This will not allow internal resonances to develop which can cause m any amps of current to circulate through the input circuitry. Take the 0.5 V hit on efficiency. The real diode is so much nicer (do note I am coming at this for units that are 30W or less, usually less).

lications of a particular interrupt (for instance) waveform. I insist on d oing each one manually and slowly. Apply and observe before the next appli cation of the transient. I have seen where people try to automate these tr ansient applications and wind up making a burst of 5. I think this breaks the spirit of what is expected. I have seen the automatic test blow through them so fast that you cannot even tell what happened. I insist on manual application of transient waveforms.

well of audio frequncy ripple is OK if you are still able to properly monit or the equipment.

ests are not about how the unit operates with voltage corruptions, but rath er it is an assessment of how your unit might affect the power bus. For lo w power equipment always fight for these things to be characterized but not specified. EVERY TIME I test any of these items to a spec it fails....Esp ecially inrush current. Just characterize it!

a hard spec. It will fail. Fight to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacitors have to get charged up and yes, your EMI caps theoretically take infinite current for short durations to charge up. When you design around inrush yo u start to take away internal capacitance that you really want. The aircra ft has to tranfer energy into your unit on power up. I think the aircraft manufacturers get that but the designers see a spec as a challenge and try to meet it (at the expense of inadequate internal capacitance or being in t he crappy position of telling your management that you failed at test time) ...Actually, the customer will probably give you relief on it (not on anyth ing else though)so fight up front to avoid the headaches.

Item 16. Test procedures and reports. I could make a separate post on this ....Engineers (young ones rightfully so, I think) hate writing and testing requires a lot (A LOT) of thought to what is going to be tested and how to go about doing it. Younger engineers I think should be allowed to learn th e trade and not get bogged down by writing. But, sooner or later, I do not believe you are a good engineer if you cannot write a good test procedure. A good procedure is based upon the right data being taken and the right s etups. Engineers are normally not good at writing and unfortunately in man y corporations the procedure writer is the "lesser" engineer, but that is a bad wrap ( I have been on both sides ). If you can get past the lesser en gineer thing you can learn to use your willingness to write procedures to y our (and the programs ) advantage. The thing about procedures, is that nob ody wants to look at them until the end of the program, so if you are good, you can write the procedures to force things that you know are best for th e program. In many respects, writing the tests allows a control over the d esign the is very powerful and goes unchallenged because a design engineer will design to the test if you can get it through quick enough. I have lea rned (I am late in my career so I am taking what gets me over the finish li ne) to embrace writing procedures and reports and to use them to my (and th e programs ) advantage

Reply to
blocher

Sounds like they (at least) let you go home on the weekends.

It's when they lock you up in a box until the test report has all check marks, that your metal is really tested.

RL

Reply to
legg

It's when they lock you up in a box until the test report has all check marks, that your metal is really tested. ...... ....... Testing for checkmarks....i could have had an item dedicated to that.

Reply to
bulegoge

snipped-for-privacy@columbus.rr.com wrote in news:42c50f86-f684-4a63-bc70- snipped-for-privacy@googlegroups.com:

I think he shouldn't meddle around trying to convince folks he is intelligent.

It's a mettle thing.

Reply to
DecadentLinuxUserNumeroUno

, FIGHT, FIGHT against a hard spec. It will fail. Fi ght to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacitors have to get charged up and yes, your EMI ca ps theoretically take infinite current for short durat ions to charge up. When you design around inrush you start to take away internal capacitance that you reall y want. The aircraft has to tranfer energy into your unit on power up. I think the aircraft manufacturers get that but the designers see a spec as a challenge a nd try to meet it (at the expense of inadequate intern al capacitance or being in the crappy position of tell ing your management that you failed at test time)...Ac tually, the customer will probably give you relief on it (not on anything else though)so fight up front to a void the headaches.

m done for now...Bye

nd reports. I could make a separate post on this....E ngineers (young ones rightfully so, I think) hate writ ing and testing requires a lot (A LOT) of thought to w hat is going to be tested and how to go about doing it . Younger engineers I think should be allowed to lear n the trade and not get bogged down by writing. But, sooner or later, I do not believe you are a good engin eer if you cannot write a good test procedure. A good procedure is based upon the right data being taken an d the right setups. Engineers are normally not good a t writing and unfortunately in many corporations the p rocedure writer is the "lesser" engineer, but that is a bad wrap ( I have been on both sides ). If you can get past the lesser engineer thing you can learn to us e your willingness to write procedures to your (and th e programs ) advantage. The thing about procedures, i s that nobody wants to look at them until the end of t he program, so if you are good, you can write the proc edures to force things that you know are best for the program. In many respects, writing the tests allows a control over the design the is very powerful and goes unchallenged because a design engineer will design to the test if you can get it through quick enough. I h ave learned (I am late in my career so I am taking wha t gets me over the finish line) to embrace writing pro cedures and reports and to use them to my (and the pro grams ) advantage

A young adult going to a 4 ye ar college and not coming out of it knowing how to r ead & write much better than when they went in is not money well-spent.

An engineer who is an engineeri ng genius but cannot express him/herself in a way th at other people understand easily...their value drops

considerably. Same for doctor, lawyer, and many othe r white-collar fields.

"Younger engineers I think s hould be allowed to learn the trade and not get bogg ed down by writing." So a guy comes fresh out of colle ge and he doesn't know how to engineer and doesn't k now how to write, either? Gosh, what are we paying t his fella for, anyway? Way easier to train a grad wi th an excellent command of English to be a good test e ngineer than vice versa I think...

Reply to
bitrex

If the converter doesn't have soft-start intrinsically can't you say apply a PWM "ramp" to the shutdown pin (or equivalent?) 40 cent 8 bit micro like the ATTiny series has PWM output and can do over-the-rail differential ADC to sense current, works great

Reply to
bitrex

nst a hard spec. It will fail. Fight to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacit ors have to get charged up and yes, your EMI caps theoretically take infini te current for short durations to charge up. When you design around inrush you start to take away internal capacitance that you really want. The air craft has to tranfer energy into your unit on power up. I think the aircra ft manufacturers get that but the designers see a spec as a challenge and t ry to meet it (at the expense of inadequate internal capacitance or being i n the crappy position of telling your management that you failed at test ti me)...Actually, the customer will probably give you relief on it (not on an ything else though)so fight up front to avoid the headaches.

this....Engineers (young ones rightfully so, I think) hate writing and test ing requires a lot (A LOT) of thought to what is going to be tested and how to go about doing it. Younger engineers I think should be allowed to lear n the trade and not get bogged down by writing. But, sooner or later, I do not believe you are a good engineer if you cannot write a good test proced ure. A good procedure is based upon the right data being taken and the rig ht setups. Engineers are normally not good at writing and unfortunately in many corporations the procedure writer is the "lesser" engineer, but that is a bad wrap ( I have been on both sides ). If you can get past the lesse r engineer thing you can learn to use your willingness to write procedures to your (and the programs ) advantage. The thing about procedures, is that nobody wants to look at them until the end of the program, so if you are g ood, you can write the procedures to force things that you know are best fo r the program. In many respects, writing the tests allows a control over t he design the is very powerful and goes unchallenged because a design engin eer will design to the test if you can get it through quick enough. I have learned (I am late in my career so I am taking what gets me over the finis h line) to embrace writing procedures and reports and to use them to my (an d the programs ) advantage

.

I don't think most engineers wish to go into testing at the beginning of th eir career. I think they should learn the nuts and bolts for 10 years or so . Well, actually I think most would prefer to do the nuts and bolts. Most engineers are known for their in-ability to write. But you are correct, a t some point one diminishes their value if they cannot write. Writing is w here all the corporate persuasion takes place and if you are not in the per suasion game then you are not a player.

Reply to
blocher

st a hard spec. It will fail. Fight to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacito rs have to get charged up and yes, your EMI caps theoretically take infinit e current for short durations to charge up. When you design around inrush you start to take away internal capacitance that you really want. The airc raft has to tranfer energy into your unit on power up. I think the aircraf t manufacturers get that but the designers see a spec as a challenge and tr y to meet it (at the expense of inadequate internal capacitance or being in the crappy position of telling your management that you failed at test tim e)...Actually, the customer will probably give you relief on it (not on any thing else though)so fight up front to avoid the headaches.

These inrush currents are the very fast loading of the capacitors on the in put power rail. They occur in the 100's of usec time frame and are all do ne before the power supplies are even close to being at regulation.

Reply to
blocher

Our trade is to produce documents.

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
 Click to see the full signature
Reply to
jlarkin

inst a hard spec. It will fail. Fight to characterize it. Low power stuf f is not going to take down the aircraft power bus and your internal capaci tors have to get charged up and yes, your EMI caps theoretically take infin ite current for short durations to charge up. When you design around inrus h you start to take away internal capacitance that you really want. The ai rcraft has to tranfer energy into your unit on power up. I think the aircr aft manufacturers get that but the designers see a spec as a challenge and try to meet it (at the expense of inadequate internal capacitance or being in the crappy position of telling your management that you failed at test t ime)...Actually, the customer will probably give you relief on it (not on a nything else though)so fight up front to avoid the headaches.

this....Engineers (young ones rightfully so, I think) hate writing and tes ting requires a lot (A LOT) of thought to what is going to be tested and ho w to go about doing it. Younger engineers I think should be allowed to lea rn the trade and not get bogged down by writing. But, sooner or later, I d o not believe you are a good engineer if you cannot write a good test proce dure. A good procedure is based upon the right data being taken and the ri ght setups. Engineers are normally not good at writing and unfortunately i n many corporations the procedure writer is the "lesser" engineer, but that is a bad wrap ( I have been on both sides ). If you can get past the less er engineer thing you can learn to use your willingness to write procedures to your (and the programs ) advantage. The thing about procedures, is tha t nobody wants to look at them until the end of the program, so if you are good, you can write the

any respects, writing the tests allows a control over the design the is ver y powerful and goes unchallenged because a design engineer will design to t he test if you can get it through quick enough. I have learned (I am late in my career so I am taking what gets me over the finish line) to embrace w riting procedures and reports and to use them to my (and the programs ) adv antage

s.

Yes, engineers are the keepers and producers of documents , and yet, I do n ot recall one time in this forum where you pointed us to a photo of your la test and greatest document.

Reply to
blocher

gainst a hard spec. It will fail. Fight to characterize it. Low power st uff is not going to take down the aircraft power bus and your internal capa citors have to get charged up and yes, your EMI caps theoretically take inf inite current for short durations to charge up. When you design around inr ush you start to take away internal capacitance that you really want. The aircraft has to tranfer energy into your unit on power up. I think the air craft manufacturers get that but the designers see a spec as a challenge an d try to meet it (at the expense of inadequate internal capacitance or bein g in the crappy position of telling your management that you failed at test time)...Actually, the customer will probably give you relief on it (not on anything else though)so fight up front to avoid the headaches.

on this....Engineers (young ones rightfully so, I think) hate writing and t esting requires a lot (A LOT) of thought to what is going to be tested and how to go about doing it. Younger engineers I think should be allowed to l earn the trade and not get bogged down by writing. But, sooner or later, I do not believe you are a good engineer if you cannot write a good test pro cedure. A good procedure is based upon the right data being taken and the right setups. Engineers are normally not good at writing and unfortunately in many corporations the procedure writer is the "lesser" engineer, but th at is a bad wrap ( I have been on both sides ). If you can get past the le sser engineer thing you can learn to use your willingness to write procedur es to your (and the programs ) advantage. The thing about procedures, is t hat nobody wants to look at them until the end of the program, so if you ar e good, you can write the

many respects, writing the tests allows a control over the design the is v ery powerful and goes unchallenged because a design engineer will design to the test if you can get it through quick enough. I have learned (I am lat e in my career so I am taking what gets me over the finish line) to embrace writing procedures and reports and to use them to my (and the programs ) a dvantage

ng

f

lds.

t

not recall one time in this forum where you pointed us to a photo of your latest and greatest document.

Let me elaborate. you have shown various napkin style schematics... I am not sure why I am getting pushback on the point that young engineers ought to focus on design and building things and not be pushed into procedure wri ting when they fist get out of school. I cannot imagine a young engineer w ho would choose writing a procedure over building a circuit. Does a SW guy want to write code or write verification cases? It takes years to get goo d at engineering and I do not think writing is the best place to put a youn g engineer. I am surprised I am getting challenged on that

Reply to
blocher

I have been frequently assigned to power supply testing (and some design) per MIL-STD-704 and DO-160.

normal operation" - which have a few subtleties) the important thing is tha t if 28V (typical nominal voltage for my category of equipment) is present on the input the box better be working. It is surprising how difficult tha t simple requirement is to achieve. The testing regiment requires the unit to be put through many types of over/under voltage tests that will take th e box down and then the requirement is that the unit re-powers up without u ser intervention and works correctly. This is not a trivial requirement. Much of the testing really revolves around the standard's notion that this is not a trivial requirement.

e and beyond those in DO-160. In one case they require 8 waveforms that im pose glitches on the startup voltage when powering up. Sure enough, we ran these waveforms and one of their sequences locked our unit up (power was a pplied to the terminals and the unit was latched up and required user inter vention to power it off and back on to get it to work).

.....oh boy , this requires a lot of attention to get it right.

t times, to educate my management that most of the time I find a problem it is in the setting up of the required waveforms. Say I have an undervoltag e requirement of 12 Volts and as I am setting it up I apply 11 volts and th e unit locks up. The first thing a manager tries to do (until properly edu cated....fortunately my mangers do try to do the right thing....most of the time) is to ask if the unit works with the specified waveform and I have t o answer yes.....but.....The real purpose of the test is to make you look a t the unit 100 different ways to Sunday to see if the unit latches up and p art of the process is the setup variations that will frequently be where th e sweet (sour) spot is. So I have to go back and remind them that if I can have 28V appllied to the box and it is latched up it really does not matter what I did to the unit before ---the box not adequate for an aircraft. (o f course this whatever you do are within reasonable guidelines....undervolt ages, short duration overvoltages and some ripple on the input voltage). W hen a manager tries to tell me to just run the waveforms I ask him if we ca n have this discussion with the customer to get clarification.....99% of th e time that forces the required (and painful) design changes.

k MIL-STD-704/DO-160 is rigorous you should see what one well known aircraf t manufacturer in France requires in addition to DO-160. It takes weeks to run the tests.....They do not want a box to latch up on their aircraft

pplied that the unit is expected to work through. The aircraft manufacture rs HATE HATE HATE latchups, but they also do not like the unit temporarily shutting off when it should not shut off. These normal operation requiremen ts revolve around3 basic things 1. the unit will stay powered up for 200 ms (this can vary) when power drops below a specified voltage (hold-up cap re quired) 2. The unit will stay powered up when over voltages are less than 2

00 ms 3. The unit will operate through various audio frequencies imposed on top of the DC voltage. 4. The unit will operate from typically 16or18V to approximately 29-33 volts (each unit will have these nailed down exactly in a spec)

ot cause the unit to latch up (per above) and also not damage the unit (OK thats obvious, but it is explicitly stated and required).

n Ideal diode (smart FET) is used instead of a schottky diode on the input. Yeah they work for negative voltages....but About those Audio frequencie s imposed on the DC lines..... , they walk right through the ideal diode. I am of the persuasion to use a schottky diode with a large capacitor afte r it. This will not allow internal resonances to develop which can cause m any amps of current to circulate through the input circuitry. Take the 0.5 V hit on efficiency. The real diode is so much nicer (do note I am coming at this for units that are 30W or less, usually less).

lications of a particular interrupt (for instance) waveform. I insist on d oing each one manually and slowly. Apply and observe before the next appli cation of the transient. I have seen where people try to automate these tr ansient applications and wind up making a burst of 5. I think this breaks the spirit of what is expected. I have seen the automatic test blow through them so fast that you cannot even tell what happened. I insist on manual application of transient waveforms.

well of audio frequncy ripple is OK if you are still able to properly monit or the equipment.

ests are not about how the unit operates with voltage corruptions, but rath er it is an assessment of how your unit might affect the power bus. For lo w power equipment always fight for these things to be characterized but not specified. EVERY TIME I test any of these items to a spec it fails....Esp ecially inrush current. Just characterize it!

a hard spec. It will fail. Fight to characterize it. Low power stuff is not going to take down the aircraft power bus and your internal capacitors have to get charged up and yes, your EMI caps theoretically take infinite current for short durations to charge up. When you design around inrush yo u start to take away internal capacitance that you really want. The aircra ft has to tranfer energy into your unit on power up. I think the aircraft manufacturers get that but the designers see a spec as a challenge and try to meet it (at the expense of inadequate internal capacitance or being in t he crappy position of telling your management that you failed at test time) ...Actually, the customer will probably give you relief on it (not on anyth ing else though)so fight up front to avoid the headaches.

Interesting...

Reply to
bloggs.fredbloggs.fred

the

Photo of a document? Sort of like the cover of a book?

I have posted lots of photos of circuits and experiments. And posted many Spice sims.

You can go to our web site and download manuals. I wrote a lot of them.

I see so many ugly Spice sims, with nothing to indicate what they are or who created them when. Just a heap of parts. And I see a lot of spreadsheets full of numbers, again no author, date, context, or a simple statement of what it *is*. Sims and spreadsheets like that will be useless in a year or so; nobody will remember what they were for.

I have to teach the kids this stuff. And how to draw, and how to read drawings. I guess EE schools don't teach engineering graphics any more.

formatting link

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
 Click to see the full signature
Reply to
jlarkin

And sheets of the schematics of actual products. And scope shots *in focus* *with* post-its furnishing context. And screen caps of Spice sims, and .asc files.

They should learn to document their output properly, from day 1.

Don't college tests and lab reports note subject, author, date? They can keep doing that when they get a job.

I have no use for an engineer, of any age, who cannot transfer learned knowledge to others in a disciplined way. I don't pay people to amuse themselves privately. To "build a circuit" and not document it.

If they can't document their work clearly, so that others can benefit, they will never be good at engineering.

--
John Larkin         Highland Technology, Inc 

lunatic fringe electronics
 Click to see the full signature
Reply to
jlarkin

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