Control Panel Mystery

[Summers420us]

DocBrown and JMRanger... glad you all know what your talking about

Personally, the discussion has gotten a little above my pay grade. I would love to learn more though, but at this point it sounds a bit "Greek".

I will go home and post the specs of the Radio Shack LED I am trying to use in my US spec board. I can live with a little LED chatter when the fan kicks on and off, that won't kill me, but I really would like a nice bright blue LED on the board instead of the dim green one to show when the fridge is lit.

[DocBrown]

Vanagonner:

The blue LED for the high beams is my touch. Mine was green before I swapped for blue. Who ever heard of a green high beam light? Blue LEDs weren't really available until the late 90's. Hard to make good gallium Nitride wafers.

JMRanger:

I ought to read things before opening my mouth...er....keyboard

If the amp only puts out 3V it's not surprising that Summers420 doesn't get any light. Blue LED knee voltage is easily 3 V, possibly 4 or more.

Lane:

Don't worry about the 'geek-ese'. If you can solder you can make this work. And I know you can solder because you already swapped LEDs. In 'simple-ese', the amplifier takes the miniscule voltage from the thermocouple (0.01 V or so) and, well, amplifies it. According to JMR, after amplification in a stock circuit the signal is about 3V. that's enough to drive 1 mA or so through a red or green LED in this circiut, enough to make a bit of light. 3V will barely turn on a blue LED, particularly an old tech RadioShack one, let alone light up your cabin.

So if you want a blue LED (and, frankly, who doesn't?) you need to get the voltage up a bit by increasing the amplification. That is easily done by changing R12, the one directly under the switch in your photo, with colours brown-black-green (and probably gold). That colour code stands for 1 Megaohm. The overall amplification of the circuit varies in proportion to this resistor. Make it 2 megaohms and if the output was 3V it should go up to about 6V.

First I would check that the voltage at pin 1 of the amplifier (Right hand chip in the photo, top left hand corner pin) with the fridge lit to verify that it really is ~3 V. If so, swap the 1M resistor for something a bit bigger, I'd start with 1.5M or 2M. Experiment a bit. That alone may be enough to get the LED to turn on nicely. If you make R12 too large, the LED might not turn off. If you want it brighter still, you could then try lowering the value of R10 (it connects to the soon-to-be-blue LED on one side and limits the current through the LED). R10 is 1.2kohms, try something in the 330-1k ohm range.

Don't go ape with brightness, that RadioShack LED is not going to last too long if you drive it too hard.

As for the capacitors that I mentioned, if the flickering bothers you buy a 47 uF 25V (or higher) capacitor and ADD it to the back side of the circuit board, solder the -ve terminal to somewhere that is grounded (connected to the trace that has the black wire soldered to it) and solder the +ve terminal to the 12V supply (somewhere the orange wire is connected to). Make sure you get it soldered the right way round or it will live a short but exciting life....

If all that still seems too nasty, you could just get a better LED. The one I mentioned in my other post would probably work fine without any other modifications.

[jmranger]

[Summers420us]

Thanks for all the help

So here is my task list:

1. Post the voltage at pin 1 with fridge burning LP.

2. Post close up of bard so that colors of R10/R11/R12 can be seen.

3. Post info on the Radio Shack LED p/n 276-0311 that I am attempting to use.

I wonder if the LED I have is bad. Do you recommend testing it momentarily by attaching directly it to my 12v test battery or do you think this will burn it out?

I have also seen mention of these Radio Shack part numbers being used: 276-311 and 276-316. Is it possible I have the wrong one?... I thought 276-0311 was the same as 276-311, but maybe I was mislead by the counter jockey at Radio Shack.

More to follow after I finish my homework.

[DocBrown]

Lane:

1. Correct
2. Correct
3. If you can find it

If you hook up the LED directly to 12V then it will live a short but exciting life, and you will get to go buy a new one

I suspect that the issue here is that RadioShack doesn't make blue LEDs. They get a deal on a bunch with some vague specifications and sell them. I imagine that you have an old tech LED. LEDs made today have lower knee voltages and produce far more light with far less current than those made even a few years ago. That lumex brand diode I have puts out a huge amount of light with a few hundred microamps of current. So as I said, a new LED (from digikey where you know what you are getting) will probably do the trick with no other modifications.

The other variable is the thermocouple. There is probably a lot a variation in how hot these get with the fridge on...10mV or 40 mV? But that will show up in your measurement of pin 1 voltage. Maybe your thermocouple doesn't get so warm as JMR's.

[Summers420us]

Thanks Doc... I won't test the LED that way then.

I believe this is the LED you are suggesting to use as a replacement:

http://parts.digikey.com/1/parts/685070-led-5mm-blue-blue-diff-lens-ssl-lx5093usbd.html

If everything checks out good after I finish my "homework" from above, then I will order one of these.

[DocBrown]

Exactly what I have in my dash for a high beam light.

While you are at digikey, for a few pennies more you could equip yourself with a small selection of resistors (in case you need to fool around with the gain), possibly a capacitor (to stop the flicker with the fan) and possibly other goodies like fans for the fridge (I use a small 12 V fan on the inside). Digikey has a minimum order otherwise they hit you with handling charges. In other words, it pays to think ahead when you get stuff there.

Particularly if you're a cheapskate like me.

[DLJ]

I have worked on many of these refers. You have the wrong LED panel, its from an earlier unit. On right side ,top to bottom, Green, yellow and red are water tank level indicators. Last (or 4th) is green, this is your flame indicator. On right side is, top to bottom, Grn, yellow, red. A simple battery charge indicator. All newer models have a toggle switch at top middle.

[jmranger]

[Summers420us]

[DLJ]

Very sorry----I should have read all the way through. The panel you have from Pick-Pull looks correct. Also I dont think the Canadian panel is any different from US model. The difference seems to be the year. I upgraded my LED but now I feel its a little too bright. Its all trade-off I guess.

[Summers420us]

I finally got out there to mess around with the control panel again.

Fisrt off, I could not resist and I tested the LED with a quick touch to a 10V power source (dead motorcycle battery) and it lights up just fine, so we can rule out a dead LED.

I also verified with Radio Shack that p/n 276-0311 is the same as p/n 276-311. Here is the packaging... as you can tell, I pulled the old "kid at Christmas" routine and destroyed the packaging, but perhaps some of what is left is helpful:

Next Up... a nice pic of my board with JMRangers numbering applied to it. R10, R11, and R12 appear to have the same color codes as JMRanger's but other items on the board look a tad different. Unfortunately during testing I crossed post 3 and 4 of chip V2 with my probe and delaminated the board on the back. It still has continuity through the circuit and the Green Pilot LED still lights as well as the Battery indicator LEDs. I don't think I completely "smoked it"... do you? Ideas for relaminating it? Should I just leave it alone? Test results were the same before and after this accident.

And here are my test results
Voltage of Chip V2 between Pin 1 and Pin 3 (using Pin 3 as ground) and with my MultiMeter set at the 2V DC scale:
.0120 with the fridge not lit and with power to the panel
-OL with the fridge lit and with power to the panel. I measured this a bunch of times and could not get a reading. Everytime I touched the two pins with the fridge lit, the display changed from 0.000 to -OL. I even tried using a frame ground instead of pin 3 and got the same result.

Next I tested the votage at the Pilot LED pins with the fridge lit and power to the panel and got 1.805

I noticed that the green battery light is about twice as bright as the green Pilot LED so I checked it's pins too and found 1.958

So... where to go from here? I have not purchased any additional LED, and if I can grab a cheap resistor from Radio Shack that will do the trick, then perhaps that is the best idea...

[DocBrown]

Sorry to be the bearer if bad news, you'll need to do a few measurements again. OL means overload, i.e. more than the highest voltage on that scale setting (2V). So you'll need to measure the OLs again with the meter on the next lowest setting (probably 20V).

If your solder trace is lifting but still functional I'd be inclined to leave it alone. Maybe throw a piece of clear packing tape over the trace WHEN YOU"RE DONE MUCKING ABOUT WITH THE SOLDERING IRON just to stop it going anywhere. If you break a solder trace you'll need to bypass the break with a bit of wire, but if everything is still working then you're probably OK. The good news is that this particular mistake only (!) directly connected 12V to ground. Short circuit. Not likely to have fried anything other than the copper trace which simply got very hot and the glue let go.

The RadioShack LED is, as I suspected, a bit of a brute. 5V and 30 mA. That's not going to light up very much with a 3V signal. But if you make the gain mod (change the 1M resistor to 2M) then you have 6V to work with which should be tickety-boo. And with a 30mA rating it's going to be hard to kill by overdriving with the low power amplifiers in this circuit.

The difference between illumination of the two green LEDs is, as you can see, the brighter one has a slightly higher voltage across it and is likely drawing more current.

[Summers420us]

I redid the tests using the 20V scale. I used a frame ground, and tested the voltage from pin one (top left pin) of chip v2. The fridge was lit on propane.
2.87 - fridge lit and fan on back off
4.04 - fridge lit and fan on back on

Can you tell me, using the numbers that I added to the pic of my board:
Which resistor I need to change?
What identifies the one I have as a 1M?
What color rings will be on a 2M one?
Is the resistor you are suggesting to change, only on the Pilot LED circuit? I want to be sure I will not effect the rest of the functionality of the board.

Now... I want to also tell you about what the board is doing. When the fan kicks on, all the lights on the board very quickly blink once. While the fan is on (entire duration), the Pilot LED, and perhaps the others as well, are much brighter (more voltage as shown from testing above). About every third of fourth time that the fan cuts off, all the battery sensor LEDs come on and the pilot LED goes out. It stays this way for about 1 or 2 seconds. Then everything returns to normal. As I am adding this BLUE LED to the board, I would also like to take the opportunity to fix this issue if I can. If you have an idea on how to fix it, please let me know, just try to give it to me in "laymans terms"

Also on a side note, the fan is cycling much too frequently. 15 seconds on then 15 seonds off and repeat. Nobody else has told me how often their fan cycles, but many people said this is too fast. I am using this fan:
http://www.gowesty.com/ec_view_details.php?id=3470&category_id=204&category_parent_id=

It has been suggested that I pull the fridge and reconnect the thermoswitch, the object marked "oC" in the pic below.

And when reconnecting the thermoswitch, I should use some sort of thermal grease. Radio Shack sells this... will this work?

Also suggested was to add a vent to the outside by removing the city water port, but that project will be on hold for a while.

As for the delamination... I was thinking nail polish might stick the copper trace back to the board and then I can put a coat over the top of it to insulate it again... how does that sound? Tape will be difficult to get to lay flat in that area.

[DocBrown]

Good work.

If you are happy with the intensity of the LED with the fan on then 4V is enough to drive a decent current through your LED. Then you need to increase the gain of the amplifier by the ratio of 4.04 to 2.87 or 1.39. Increasing the 1M resistor to 1.39 would do the trick. The catch is that if you ask for a 1.39M resistor at RadioShack, they'll laugh at you (actually they'll probably just stare blankly.....). But 1.5 M is a resistor that you can actually buy. So I'd go with that. If you can't get a 1.5M but can get a 2M that would be OK, too, you may find the LED too bright then. After replacing the 1M (R12 in JMR's schematic) with either of the larger options, you can adjust the brightness t taste by adjusting R10 (1.2k). Make R10 smaller to make the LED brighter and vice versa.

Resistor value is read from the colour code, see for eg: http://www.elexp.com/t_resist.htm

The circuit board you have will be all 4 band resistors, only 3 of which are really important for you. So 1 Meg is brown-black-green-(something) where the something is probably gold. That stands for a "1" a "0" and 5 more "0's" or 1,000,000 ohms = 1M. The gold just says that it's within 5% of the stated value. Which is close enough for us.

If you want to get a 1.5M it would be brown-green-green. Your homework assignment is to figure out what a 2M resistor would be:)

The 1.2k resistor, should you need to replace it, is brown-red-red.

These two resistors only affect the pilot light. Nothing else.

Nail varnish might work well for gluing the trace back down. Acetone would remove it should you need to solder in there again.

Now on to your fan issue. In layman's terms, it's buggered up.

It sounds to me like the fan has a loose connection of some sort. Or perhaps the main power supply to the fridge-sink unit has a loose power or ground connection. This one is going to be a bear to find.

My fan cycles over seconds or minutes. No rhyme or reason. But my lights don't dim

I suspect my thermoswitch is whacked. If you do replace or mess with the thermoswitch, that thermal paste would be a good idea.

[shepherdsond]

I am resurrecting this post since my problem seems relevant.

Rather than my fridge led not working (the case for the op) it just yesterday went into a mode where it is allways lit whether the fridge is lit or not. I am guessing it's something to do with the thermo couple but am surprised that the failure mode would be on rather than off. Any ideas of what to look for?
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[Summers420us]

Been a long time, but I fionally got back to this project. The Radio Shack LED just required too much power. I am only getting 2.5V when pilot is lit, so I bought and installed this and it works great!

http://parts.digikey.com/1/parts/685070-led-5mm-blue-blue-diff-lens-ssl-lx5093usbd.html


I also installed the capacitor mentioned above and that did smooth out the lights when the fan kicks on and off.

Now I am sorting out why the fan cycles so rapidly. One thing I have found is that with the fridge pulled, and air circulating freely, the fan has yet needed to kick on. Now I put the thing in a cardboard box to emulate being in the cabinet. Wish me luck!

[Typhon2222]

Folks, hoping I can milk the amazing collective wisdom of this site.

While trying something really stupid recently, I managed to break the circuit board itself of the LED indicator panel. I broke off an entire corner, the top-right corner containing D2 (diode 2) in the pic below.

That left the whole panel inoperative.

So in desperation, I soldered a new connection with wire that just jumps over that missing corner and diode entirely.

Things seem to work. Water level indicator and fridge indicator seem fine. Battery indicator too, though I think it's overestimating battery strength now: seems to show green when it showed yellow before, and shows yellow when it used to show red. I think, anyway.

Just wondering: what the heck did that diode doo? Am I running any risks now that it's out of the picture and the circuit just skips it entirely?

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[r39o]

Don't guess. Put the diode back. It looks like it could find a new home in the middle of the board. Just follow the traces.

I bet it is a reference or blocking diode. If reading high one could guess the voltage drop provided by a series blocking diode would be important and also, maybe, protect from reverse connections. Or as a reference for the IC. Note that if it is a reference then you will likely need that specific part number diode. If blocking almost any will do. Hard to tell from the picture.

Put the diode back.
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[Ahwahnee]

Can't answer if that is okay, but...