Probably trivial, but I'm a programmer - not a ee

Den fredag den 5. december 2014 01.55.13 UTC+1 skrev snipped-for-privacy@gmail.com:

3-1-2

-Lasse

Run the lamp from a DC current source, use a resistive divider to reduce the voltage to something suitable

another option would be to sound the chimes after every reset :) but seriously, that sounds like it's hooked up wrong.

fist thing I'd do is check the voltage of the lamp in the bellpush those things are usually wired in series with the bell solenoid so they don't see the full supply voltage. Is the supply 12V AC or something else?

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umop apisdn

Worst case is less than twice as much as usual heat output of the lamp in the bellpush. (that when someone's leaning on the button) usually less than the heat from the lamp.

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umop apisdn

Don't use a rivet, use a bolt and spring washer, or a clip, rivets can crack the case.

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umop apisdn

On a sunny day (Thu, 4 Dec 2014 12:03:21 -0800 (PST)) it happened snipped-for-privacy@gmail.com wrote in :

Use optocouplers, always, I remember I wired an alarm system in the old house, and we went on holiday. The doorbell was sitting next to the alarm sensor wiring. Any time when somebody ringed the bell the alarm went off, a big horn at the front, police came to look, neighbours.. The bell sparked a bit when used, that was enough to trigger the micro, even with alarm contacts closed. Optos fixed that.

Have it play a canon, with the theme starting up when the button is pressed, and the contrapuntal theme starting up when the button is released (or on subsequent button presses, if the tune isn't finished).

The only downside to this is that if you do it right, even family members will want to ring the bell before entering the house.

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Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com

[snip]

Just buy one...

And it's loud enough I can hear it without my hearing aids in place ;-) ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| 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.

Boring.

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www.wescottdesign.com

Telephones and doorbells have simple functions. What is gained by trying to make them into entertainment centers ?>:-} ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| 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.

Exactly that! Entertainment. Are you some sort of curmudgeon or something?

--

Rick

Why, fun, of course.

--

Tim Wescott 
Wescott Design Services 
http://www.wescottdesign.com

My shipment of LM317 arrived today, and I must say that your schematic work ed perfectly. I'm still experimenting with resistors to get the current to the button down, and to achieve the correct voltage out for the arduino - but it's more success than I had on my own. The arduino doesn't reset on b utton press, and as described - voltage drops to zero when the button is pr essed.

Thanks again!

It's kinda like reading newsgroups, only you actually make something. Mikek :-)

"rickman" is one of our resident ignoramus (whatever the plural is

He is INDEED, outstanding ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| 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.

m:

rked perfectly. I'm still experimenting with resistors to get the current to the button down, and to achieve the correct voltage out for the arduino

- but it's more success than I had on my own. The arduino doesn't reset on button press, and as described - voltage drops to zero when the button is pressed.

hahaha, so - exploding voltage regulators.... My wife was not pleased, a p iece flew in her direction and she nearly jumped out of her skin. "Are you trying to burn the house down??" she yells.

In the circuit Lasse provided, there were no resistor values - so I was exp erimenting to determine the minimum current necessary to keep the bulb lit (and then maybe raise it a little higher to accommodate power fluctuations) . Apparently I started too low and/or held the button too long. My earlie r tests, I only held the button for less than a second.

39ohm resistor + long button press = exploding regulator

Any suggestions for a lower resistance limit on the LM317 adjust to avoid f uture pyrotechnics? Am I mistaken as to the cause - do I need a more robus t heat sink, was it heat related? I'm thinking my next attempt will be at

240ohm, but I don't want to get yelled at twice for the same thing.

Depends on your circuit voltage. I believe the voltage the regulator is set for is 1.25 volts across the 39 ohm resistor gives 32 mA. If the regulator has to drop 12 volts DC that is 0.384 Watts. Nearly 0.4 Watts shouldn't be too much for the LM317. Is this in a TO-220 package? I don't have the data sheet handy, but it should not make it explode in any short order. I suspect you got your hands on a 3.9 ohm resistor or maybe shorted the leads.

These days most regulators are power protected, but the LM317 is pretty old. Newer devices are designed to limit the current when they over heat to prevent exploding and the rest of the circuit.

Any idea what voltage and current the bulb sees in normal operation? Once you know that you can set the current exactly rather than experiment. If you have plenty of voltage margin you can add a dropping resistor to help spread the power so the LM317 doesn't have to take it all. For example, if the lamp sees 6 volts in a 12 volt circuit, you can use a resistor before the LM317 to drop 4 volts greatly reducing the power in the LM317. If the lamp sees most of the 12 volts then you can't use a power limiting resistor and will have to do something else to deal with the power.... but that all assumes your explosion was because of a properly wired circuit needing too much current and not a bad resistor value.

--

Rick

com:

worked perfectly. I'm still experimenting with resistors to get the curre nt to the button down, and to achieve the correct voltage out for the ardui no - but it's more success than I had on my own. The arduino doesn't reset on button press, and as described - voltage drops to zero when the button is pressed.

a piece flew in her direction and she nearly jumped out of her skin. "Are you trying to burn the house down??" she yells.

experimenting to determine the minimum current necessary to keep the bulb lit (and then maybe raise it a little higher to accommodate power fluctuati ons).. Apparently I started too low and/or held the button too long. My e arlier tests, I only held the button for less than a second.

id future pyrotechnics? Am I mistaken as to the cause - do I need a more r obust heat sink, was it heat related? I'm thinking my next attempt will be at 240ohm, but I don't want to get yelled at twice for the same thing.

I'm fairly certain there were no shorts. I'm using a breadboard and insula ted jumpers, and I've never had a problem with this breadboard before.

The lamp does take 12v in normal use.

Searching other forums, I've only come across a few instances where a LM317 exploded and most of those came to the conclusion that it was a faulty uni t.

For my project, I need only 4 (2 per doorbell) - and I ordered 20.

As I understand it, the higher the resistance - the lower the current from the LM317. Perhaps I should start high and work my way down until the lamp lights instead of starting low and waiting for the lamp to go out.

Something doesn't add up. Less than half a watt should not have "blown" the device. Overheat and stop working maybe. I guess it is possible that it shorted internally, but I doubt it was from overheating.

I said "measure" the voltage and current. In this application the transformer is supplying a voltage and limits the current when the button is pushed shorting the output. So the transformer has significant resistance and that will lower the voltage to the bulb when the bulb draws current. So what is the *actual* current and voltage for the bulb in the existing circuit?

Sure, anything is possible.

E = I*R or in your case R = E/I, E is the regulator voltage which I think someone said was 1.25 volts. Now pick your current to match the bulb current when lit and calculate the resistance. Until you know the bulb current you won't be able to figure out the power level in the regulator.

You didn't answer my question about the LM317 package. Is it a TO220? Is it a rectangle about three quarter inch long with a mounting hole?

--

Rick

e:

l.com:

ic worked perfectly. I'm still experimenting with resistors to get the cur rent to the button down, and to achieve the correct voltage out for the ard uino - but it's more success than I had on my own. The arduino doesn't res et on button press, and as described - voltage drops to zero when the butto n is pressed.

d, a piece flew in her direction and she nearly jumped out of her skin. "A re you trying to burn the house down??" she yells.

as experimenting to determine the minimum current necessary to keep the bul b lit (and then maybe raise it a little higher to accommodate power fluctua tions).. Apparently I started too low and/or held the button too long. My earlier tests, I only held the button for less than a second.

void future pyrotechnics? Am I mistaken as to the cause - do I need a more robust heat sink, was it heat related? I'm thinking my next attempt will be at 240ohm, but I don't want to get yelled at twice for the same thing.

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sulated jumpers, and I've never had a problem with this breadboard before.

M317 exploded and most of those came to the conclusion that it was a faulty unit.

rom the LM317. Perhaps I should start high and work my way down until the lamp lights instead of starting low and waiting for the lamp to go out.

the lm317 has, internal current limiting, thermal shutdown, and safe area c ompensation.

so unless it is connected backwards and/or it is an "LM317" from wonghunglo w I don't see it exploding

-Lasse