DiyLightAnimation
Hardware => Lynx Express => Topic started by: Creativehues on July 03, 2013,
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I just finished building my first LE. When I run the built in test I'm having an issue with the #4 and #6 LEDs not illuminating.
I have checked and retouched the solder points on the chip holders and LEDs. The chip pins are not bent. I've switched Chips with known working ones with no change.
I need help to determine my next step. Thanks in advance.
- John
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Do you actually have power on channel 4 and 6 and just the LEDs do not illuminate?
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Thanks Dan. No power detected on either. So what does mean?
- John
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Can I use my meter to troubleshoot this further? If so, how?
- John
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I would try re-programming the PIC first.
Steve (from Edmonton)
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I would definitely try the PIC first as well (easy to do). I had a similar issue that reprogramming addressed, although I can't remember for sure if it was 4&6 that did not work.
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Are the LEDs installed in the correct direction?
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Now I just have to learn how to use my pickit3...
- John
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This is always the best way to learn. Where would the fun be if you had the time to learn something before using it?
If you need help with it, just ask and we are here for you.
Steve (from Edmonton)
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Yes fun!?! :-\ My wife is questioning my decision to build it myself...
I guess this may be the best way to learn. If the saying "you learn more from your failure than you do your success" is also true I'll be approaching genius level...
I think I have reprogrammed the pic, but nothing has changed. :(
I switched the pic out with a pic from a second yet to be built kit and no go with that one.
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I agree the most common reasons for these symptoms is the two LEDs in backwards.
RJ
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I agree RJ, but John stated he had no power from the two channels also, would this not mean it is the PIC or the chips?
If the chips are in backwards, will this cause this?
Check that the chips are oriented the same as the others.
Steve
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I replaced the #6 LED and still no go. When I probed it I'm not getting current to the LED.
- John
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Yes the chips are in the same. I just re-swapped the chip on #5 and with the one on #6 and no change.
- John
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Did you program the second PIC? What was the checksum when you programmed the PIC?
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I'm getting a checksum: 6538.
- John
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According to the wiki, that's a winning combination....so you are good there.
Being terribly new to this hobby myself what I'd try to do here is pull the pic chip, touch up all the solder points and then just reseat it again. Failing that I'd be heading to the airport to get a ticket to the Academy and spending some time in the troubleshooting lounge with the others who are much smarter than me.
No harm in trying my approach, but I don't think it will get you very far...but try :)
Good luck!!
Firmware Checksum
Pickit2 Pickit3
Standard 64C0 6538
I'm getting a checksum: 6538.
- John
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Swap the opto chip 6 pin chip between a channel that is working and one that is not to see if it moved.
RJ
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As RJ and drlucus have stated. checksum is good so swap out the chips. If #6 stays as no power then I would re-solder all of the connections on the PIC and the channels that are not working.
Steve
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I retouched all the connections on the pic but no change. Should I apply more a bit if solder on each joint? Right now I'm just melting what is currently on.
If I didn't have a family reunion scheduled I would be at the academy to trouble shoot this board.
- John
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Take a good look and ensure the pins on the socket actually made it thru the pc board hole; I've had a couple of that style socket where the pins bend underneath the socket when inserted.
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You need to be careful when working with the board with it powered up but,
The pic will have a pin running to the led, then the other leg of the led hooks to a pin on the opto 6 pin chip on the top side near the led. then one of the other top pins is hooked directly to 3.3 volts.
I am not where I can see the layout to tell you which pins as I am on my phone.
When the pic chip grounds the pin it allows the 3.3v to run through the opto turning on the led inside of the chip you can not see and then the current continues out the of the opto through the channel led to light it and to the ground the pic provides. When the channel is off the pic applies 3.3 v to the led and with 3.3v on both sides of the circuit no current flows. So check this. Stay away from the pin on the bottom side of the opto 6 pin as it has high voltage on it. Be careful.
RJ
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Thanks Don and RJ! I'm pretty sure I made sure the socket pins protruded through past the bottom of the board before I solder them. I will review those connections one more time.
I'm hesitant about dealing with high voltage on the lower side of the octos. I'd be more confident with a more exacting description or even a photo with the specific points to probe identified, circled or arrowed.
I'm willing to study more about the pin layout in order for me to test this safely. I'd rather not hurt myself or the board, so if anyone has a link to this info please share. Thanks!
- John
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I need to test a little later to confirm, so don't take me to the bank just yet, but looks like pin 1 of the opto (rightmost pin, side closest to LEDs) is the 3.3V pin, pin 2 (next pin to the left) is the connection to the LED.
If you are hesitant to power it up and take some readings, one thing you can do is a quick continuity check. I'd verify continuity from the pic pins for LEDs 4 and 6 to one side of the LED (traces are on top of the board). Safest way if you're hesitant is to remove the pic chip, and test from the socket (i.e, top of the board), as that will also confirm you didn't bend a pin under the socket. The common point between those two channels points you back to the pic and the pic socket.
If you have continuity, chips are in correctly, LEDs are in correctly, you really then need to get some voltage readings to see what is going on.
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Okay I have continuity between each opto and their corresponding LED. I also have continuity between the LEDs and their corresponding pins on the 24 pin socket and pic chip.
- John
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Time to do the voltage checks as RJ described.
Sent from my DROID Pro using Tapatalk 2
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Sorry guys, being a newbie to electronics, I'm feeling a bit obtuse about RJ's explanation. Reading it aloud it makes sense to me but I'm still unclear what to probe with the power on. So I guess I need to be spoon fed step by step directions.
Looking for something like "with the meter set to measure 3.3 volts, touch your red probe to pin 2 on the opto and the black probe to the..."
"Then do touch the red probe to this and black probe to this.. And you should get this..."
Again thanks for patience and support! I'm hoping that by spending my time trouble shooting this board, I'll learn enough to be better suited to teach my 6 year old son electronics. I think once he sees the LE and the DMX dongle combined with my laptop running vixen - his interest in electronics (and ultimately math and science) will be stimulated.
And if not we'll at least enjoy the holidays more with blinky flashy.
- John
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Does your meter have a diode test? If so then to see if you have a reading on the meter. This is done with power off. Check for continuity on the opto chip pin1 to pin1 on other opto chips.
thanks
Eric