Geiger Counter not working
Posted: Tue Feb 12, 2019 2:34 pm
Hi,
I recently purchased a geiger counter kit from Adafruit and put it together but it doesn't seem to work properly. I'm not getting any signals.
I checked all the solder points and they seem okay.
I tried to short the TP1 pad with the ground pin in the pulse J6, i'm able to get a signal both on piezo as well as LED.
When I measure the voltage between TP2 and ground pin, I'm barely registering 2.7 volts. This led me to believe that the Q3 transistor was needing replacement. I unsoldered it and installed a similar 2N222 (https://www.adafruit.com/product/756) transistor in its place.
I'm still registering 2.7 volts on the TP2.
I made sure all the pins on the 555 timer were correct, nothing was bent, and the solder points were good.
Here are the readings on all of the pins in the U1 timer (555)
1: 0V
2: 0V
3: 2.9V
4: 2.9V
5: 1.9V
6: 0V
7: 0V
8: 2.9V
I tried to short across the two clips ( + and - ) of the GM tube, nothing happens when I do that.
What could be the source of my problem?
Will it be okay to use 2N222 transistor for Q3, it seems from wiki page, that they are similar.
Is there any other thing I can measure voltages for, in order to figure out where the problem lies?
Thanks.
I recently purchased a geiger counter kit from Adafruit and put it together but it doesn't seem to work properly. I'm not getting any signals.
I checked all the solder points and they seem okay.
I tried to short the TP1 pad with the ground pin in the pulse J6, i'm able to get a signal both on piezo as well as LED.
When I measure the voltage between TP2 and ground pin, I'm barely registering 2.7 volts. This led me to believe that the Q3 transistor was needing replacement. I unsoldered it and installed a similar 2N222 (https://www.adafruit.com/product/756) transistor in its place.
I'm still registering 2.7 volts on the TP2.
I made sure all the pins on the 555 timer were correct, nothing was bent, and the solder points were good.
Here are the readings on all of the pins in the U1 timer (555)
1: 0V
2: 0V
3: 2.9V
4: 2.9V
5: 1.9V
6: 0V
7: 0V
8: 2.9V
I tried to short across the two clips ( + and - ) of the GM tube, nothing happens when I do that.
What could be the source of my problem?
Will it be okay to use 2N222 transistor for Q3, it seems from wiki page, that they are similar.
Is there any other thing I can measure voltages for, in order to figure out where the problem lies?
Thanks.