How can I debug my 555 timer circuit?

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How can I debug my 555 timer circuit?

Postby makiyoung » Fri Jun 16, 2017 2:51 am

I'm trying to build an LED chaser circuit using a 555 timer and a 4017 counter. I've built the circuit successfully on a breadboard, but now that I tried to create a soldered version it just does not work.

On my breadboard version I can observe the clock signal coming out of pin 3 just by measuring the voltage there and I see a proper oscillation. On my soldered circuit there is 0V respective to ground, and no oscillation.

here is the ne555n datasheet.


I compared the voltage on all pins of the 555 in my working and my non-working circuit, and the difference I found is that I see no voltage on pins 2,6 and 7 to ground.

How can I identify the problem now? Could I have damaged the resistor, the potentiometer or the capacitors by causing too much heat during soldering (I use sockets for the ICs, so they can't be affected by the soldering)? If that is a possible problem how would I check if a component is damaged?

I checked the soldering joints and resoldered any that looked suspicious. Should I resolder every connection, or is there a way to locate the potential bad soldering joints?

This is the schematic of my circuit, pin 3 goes to the 4017 timer which I omitted from the diagram.
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Re: How can I debug my 555 timer circuit?

Postby Ross Robotics » Fri Jun 16, 2017 9:12 pm

makiyoung wrote: Could I have damaged the resistor, the potentiometer or the capacitors by causing too much heat during soldering (I use sockets for the ICs, so they can't be affected by the soldering)? If that is a possible problem how would I check if a component is damaged?


could have damaged a component, sure. You would need to probe around and see where the voltage drops off.

I checked the soldering joints and resoldered any that looked suspicious. Should I resolder every connection, or is there a way to locate the potential bad soldering joints?

This is the schematic of my circuit, pin 3 goes to the 4017 timer which I omitted from the diagram.


Sorry, I don't see any schematic.
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