Cheap Function Generator

Function Generator from eBay ($7US)
tl:dr- it sucks!

Building this went relatively smoothly until I realised I had two of the potentiometers swapped; removing them from the PCB without a heat gun was a nightmare. I wasn’t expecting much but this kit managed to fall short of even my meager expectations:

  • amplitude changes with frequency (eg 1.8Vpp minimum amplitude at 200Hz vs 500mVpp at 250kHz)
  • noisy peaks
  • frequency range selector via jumper pins instead of switch
  • tri/sin wave selector via jumper pins instead of switch
  • tri/sin/squ all have different amplitudes on the same pot position
  • square wave has its own separate output
  • no amplitude adjustment for square wave
  • frequency increases as the related pots are turned clockwise but amplitude increases as its pot is turned counter-clockwise
  • no dc offset adjustment
  • no phase adjustment
  • no pulse width adjustment
  • no synchronization trigger input
  • no power switch
  • no power LED
  • no voltage regulation

All of these issues could have been resolved with a couple of extra dollars (op-amp and regulator ICs, switches, leds etc) I bought it because it was small and cute but I doubt I’ll be using it for anything.

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