Hello everyone, I am new to the forum and fairly new to electronics.
I have designed a circuit for monitoring the water level and pressure in a model steam engine. The circuit has been tested on breadboard and works perfectly.
I have also built the circuit on stripboard which again appears to work, in that the servos move when they should.
I have however found a problem when I wanted to add some LEDs to show what the circuit was doing.
When built on breadboard the output of pin 7 on ICs 1 and 3 would swing to within a few millivolts of the +5v and 0v rails, however on stripboard the output from pin 7 of IC 1 will only go as low as 1.6v and on IC 3 as low as 0.2v.
If I remove Q2 and Q3 from the circuit the outputs behave correctly. I don't think I have done anything wrong as the servos work correctly, and I can't see any bridging between tracks.
Can someone give me a clue as to what might be going on?
Thanks
Stew

 

Did you double check the ground connections on the IC's?

 

yes w2aew, that's the first thing I checked. I even removed the sockets and soldered the ICs directly to the board. Both ICs are reading 0v on pin 4. I think they must be picking up some form of noise but I have no idea where from.
Thanks Stew

 

I dont see any decoupling capacitors on the +5 and gnd rails. Does it really work on the breadboard and doesnt work on the stripboard?

May be you can add a 100nF cap near to pin 8 and GND of each IC and add another 100uF 16V on the +5V rail.

Allen

 

...
If I remove Q2 and Q3 from the circuit the outputs behave correctly. I don't think I have done anything wrong as the servos work correctly, and I can't see any bridging between tracks.
Can someone give me a clue as to what might be going on?
Thanks
Stew

Make sure the base resistors are still the correct values and Q2 and Q3 are oriented correctly.

 

I dont see any decoupling capacitors on the +5 and gnd rails. Does it really work on the breadboard and doesnt work on the stripboard?

May be you can add a 100nF cap near to pin 8 and GND of each IC and add another 100uF 16V on the +5V rail.

Allen

Hi Allen
I added the capacitors as you suggested and it made no difference.
I then swapped around IC1 and IC3 and the 1.6v followed the IC. I have now replaced this IC and am getting 0.2v from both. I can work with this value but it is still a puzzle as to why it works differently to the circuit on the breadboard, perhaps it's because the components are much closer together on the stripboard.
Thanks Stew