Stripboard woes

Discussion in 'The Projects Forum' started by stew1954, Feb 4, 2013.

  1. stew1954

    Thread Starter New Member

    Feb 4, 2013
    3
    0
    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
     
  2. w2aew

    Member

    Jan 3, 2012
    219
    64
    Did you double check the ground connections on the IC's?
     
  3. stew1954

    Thread Starter New Member

    Feb 4, 2013
    3
    0
    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
     
  4. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    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
     
  5. tubeguy

    Well-Known Member

    Nov 3, 2012
    1,157
    197
    Make sure the base resistors are still the correct values and Q2 and Q3 are oriented correctly.
     
  6. stew1954

    Thread Starter New Member

    Feb 4, 2013
    3
    0
    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
     
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