I've used a similar technique in other circumstances. In this instance the ADC measurements of the carger circuit will determine how much energy will be dumped into the battery at any given time, again /on average/. Lead acid battery chemistry has significant hysteresis, so I do not at this time expect any major problems with this strategy. The instantaneous current at any time will be limited by the power supply, so it's not as if there will be tens of amps rushing the battery while the power transistor is turned on.
Regards,
Uncle Steve
--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
saturation will show in the primary current much more than anything on in the secondary circuit and the by detecting it you're measuring the line voltage more than any other variable.
How do you arrive at 100 ohms? I was using 200K because the value is close to the threshold where it allows something like full power to flow through the 3055. With 100k or less I was seeing my (cheap) meter show fluxuating nonsense voltages at the emitter of up to 1500V, although my scope showed nothing much amiss at lower frequency settings. I was thinking that the 3055 was somehow generating large spikes with the rising edge of the pulse, but I did not test it exhaustively.
That's what I meant. I don't like to be wrong, so it bugs me that I am not familiar enough with the nomenclature to avoid stepping on my dick. I probably should say that the PWM will limit the average /power/ going in the battery, which is what really matters.
As I understand it, volts are sort of like the size of the pipe; amperes are like the pressure or the rate of flow, and power is the throughput. Of course it isn't plumbing and there isn't any water.
Regards,
Uncle Steve
--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.
I quickly experimented with some lower value resisters and found that the primary effect of using anything lower than 10K is damage to either the 2n2222 or the BC557. The failure mode appears to be mainly permanently shorting collector and emitter, but I observed partially damaged transistors which would produce 1V at the base of Q1 in the idle state. Since I've been doing a fair bit of fooling around in the last 24 hours, it seems I've collected a half-dozen damaged transistors, which probably contributed to some of the anomalous readings I have had.
Using fresh parts and 100K between Q3 and Q2, everything is good. The battery is only drawing 1.6A at this time so I can't easily test the circuit at higher currents without draining the battery a whole lot. The ripple at the base of Q1 is still there at 60mVpp which propagates to the emitter, although I wouldn't see it without the diode. My guess is that the Sziklai pair is too sensitive for this application, but I don't really know why or what to do about it. The proximal sensitivity to mass is another concern, and I don't know whether there is an internal oscillation occuring that is amplified by a proximal mass, or whether a proximal mass is triggering the amplification of power-line hum. An extra .22uF filter capacitor on the 5V rail has no effect.
Regards,
Uncle Steve
--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.
I redrew your circuit and tried to make Q2/Q3 look like a Darlington or Sziklai.. didn't work.
One issue I have with your 'pair' is that the idea of the pair is to get more current gain. So a transistor with only a small maximum current drives the bigger transistor. I your case you've got it backwards. The BC557 has a max Ic of 100mA and the 2n2222 is 500mA. It also seems like the BC557 wiil driven right near it's max current... Maybe a beefier pnp is in order?
That's the other R1. The R1 attached to the LED is 2.2K, a mistake I updated in a later post.
I have CFL lights, a stereo, a HDTV, several laptop computers, 4G phone, oh, and there's a single fluorescent tube in the bathroom. but the signal I'm seeing at the base of Q1 (NPN) is 60/120 Hz at 70mVpp (depending on how the scope sees it) on 16V DC, and I'm only seeing the positive side of the ripple. At power on, the spikes are much larger and fall over a couple of seconds to the stated amplitude. The transformer that is powering everything has no regulator, only a bridge rectifier and a 470uF filter cap. There may be some ripple but it must be very close to the resolution that my scope LCD can display. Open-circuit voltage is 26V, which quickly drops to 19V with a 1.6A load, so I'm wondering if a 7818 regulator would clear things up, but that would necessarily introduce a different problem.
The wires hooking up anything related to Q2/Q3 are no more than four inches long; everything else (other than the 5V supply rail for the uC) is attached to the 18V rail. I can tighten things up on the breadboard a bit, but if RF is getting to the transistors through their 1" leads there's little I can do about that. ISR that antennas are sensitive to wavelength as a function of lengths, and VLF antennas are measured in the hundreds of meters. Obviously IANAEE, and I know much less about antennas than I do about transistors, which is next to zilch.
Regards,
Uncle Steve
--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.
The length of the pipe divided by the diameter is proportionally equivalent to resistance.
Volts equates to pressure
Current equates to flow rate ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Those are just the parts I have on hand, which were selected more or less at random for the purpose of experimentation. I'm not really concerned with the fact that the BC557 is 'smaller' than the 2n2222, only that there is enough juice getting to the base of the MJE3055, which appears to be true at this point. Before I hooked up the battery, I used a 36VDC permanent magnet motor and stalled it by hand to show almost 4A going through the sense resistor.
I suppose you're correct, as the diagrams of Darlington pairs don't include anything like the 100K I have installed on the Emitter of the
2n2222, and clearly the last BC557 I blew up was due to the greater driving power of the 2n2222. I see 26mA going out of the PNP. Perhaps I don't really need the BC557, and could get away with just the 2n2222 and an appropriate current limiting resistor. What led to using the PNP transistor was my initial misunderstanding of how the 3055 worked, and I assumed the base-emitter voltage of 5V meant that it should have 5V going in to it max, but I failed to appreciate that I have the 3055 and battery configured in the emitter- follower configuration. Perhaps I should move the 3055 to the other side of the battery and try again.
Regards,
Uncle Steve
--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.
Ooooops! Sorry! He is flailing quite a bit. I remember being there ;-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Volts are like PSI (pressure). Amperes are like flow-rate. Ohms are like 1/(pipe size). Watts are work performed.
Sans quantum and gravitational effects, electricity is very much like a electron fluid. There are differences, but it is a useful comparison for intuitive reasoning.
I only provide extra assholes to those already exhibiting such behavior, like our special group of posters here who are always-dead-wrong, but scream at the top of their lungs that they are correct, and name-call anyone who dares to suggest a different scenario.
I'm quite like you, I try to induce thinking. Doesn't always work :-( And I do remember "being there". In my early teens I really flailed around trying to make sense of how circuits work ;-) ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
My great lurch forward was getting an old GE manual on Germanium transistors.
My second great lurch forward was getting a technician job in MIT Building 20. I could solder ;-) And I was simultaneously taking the right circuit courses. ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
That depends on what system you're using to make a mechanical analog of an electrical system.
And the head drop through a restriction is generally some constant times the square of the flow -- quite unlike most electrically resistive materials, which make for components whose voltage drop is some constant times current^1.
(Apparently, for decades back at the dawn of electronics, people knew that the current/voltage relationship through a resistor was
voltage drop = current^x,
but measurement technology was so crude that no one was sure -- even to a factor of two -- what x was. The prime candidates were 1/2, 1, and 2. Ohm didn't figure out that resistance happened -- he was the one that showed that for nearly all materials, x = unity.)
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
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