Works only when button is pushed.

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D3MZ
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Works only when button is pushed.

Post by D3MZ »

Just assembled the Geiger counter, but I have to hold down the button (the long one that comes with the case) in order to hear the beeps.

When the button isn’t pressed: I hear the faint whine and there’s a faint glow from the red LED.

When the button is held down: the faint LED glow disappears, but the whine persists. The LED flashes and it beeps every 2-5 seconds.
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mightyohm
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Re: Works only when button is pushed.

Post by mightyohm »

That's an interesting failure mode and one that I have not seen before!

I'd check all of your solder joints. Most likely the power or ground connection to the microcontroller U2 are not connected, or there is a short somewhere else on the board.

If you send a high resolution photo of both sides of the PCB I might be able to help you troubleshoot.
D3MZ
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Joined: Tue Jan 17, 2023 6:11 pm

Re: Works only when button is pushed.

Post by D3MZ »

Thanks!

Here are two clips (unlisted) to show the behaviour:
Without holding the button down: https://youtube.com/shorts/gqpv2QvJ1Lo
Holding the button down with tape: https://www.youtube.com/shorts/_ZbEK7MJ7oI

Lights are off so the camera can pick up the faint LED glow.

Here are the photos:
IMG_1276.jpeg
IMG_1275.jpeg
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mightyohm
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Re: Works only when button is pushed.

Post by mightyohm »

Thanks for posting the photos and videos.

Few things to check:

Some of your solder joints look a little suspect. I circled some of the ones that I am not sure about in the attached photo. Ideally the solder joint should have a hershey kiss shape. I recommend reflowing some of the joints that look rough or incomplete by touching your soldering iron to them for a couple seconds and then adding a little bit more solder. You can see some more information about this here: http://mightyohm.com/soldercomic I would take a few minutes to touch up any joints that look dry or rough or otherwise suspect. The solder should completely surround and flow onto the leads. Also take a look at the top of the board, ideally you will see a little bit of solder coming up through the holes in the board. You can see on some of the resistors like R3, R4, R7 that the holes are really empty/dry, this can be a sign of a bad solder joint.

The pin that I put an orange box around is the ground pin for the microcontroller U2 and I'd take a close look at this pin and make sure it's actually going through the board and being soldered. If this pin isn't connected for any reason it might explain the strange behavior you are seeing.

Make sure that all of the pins of U2 are going into the socket. Sometimes the pins have a tendency to get folded under the chip instead of going into the socket. You'll have to CAREFULLY pry the chip out of the socket to check. You can gently pry on either side (alternating) with a screwdriver. Be careful not to stab yourself in the finger with the screwdriver or the sharp pins.

When you put U2 back into the socket make sure all the pins align and make sure it's pushed all the way into the socket.
2023-01-18_13-25-53.jpg
D3MZ
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Re: Works only when button is pushed.

Post by D3MZ »

It works! Not sure if this makes sense with your programming, but I've accidentally bent one of the IC socket pins when placing on the PCB, such that the pin never went through the other side. It might've shorted somewhere causing this unexpected behaviour.

With your help, I found this out when reflowing that there was no pin under one of the solder points.

Thank you so much!
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mightyohm
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Re: Works only when button is pushed.

Post by mightyohm »

Cool! 8-)
Congratulations on figuring that out and fixing your kit!
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