bilateral switch driving

Hello,

I have a 4016 quad bilateral switch that I am using to swap in and out resistors in an opamp circuit to vary the gain. If I connect the enable pins of my two used switches into the 5v / 0v lines powering my arduino, then it works fine, and the opam gain changes as it should.

If however I try to drive the switch pins from IO pins on the arduino - set as outputs - I don't seem to be able to get the chip to switch - even though a multimeter appears to show the voltages on the enable lines rising and falling as they should.

Any suggestions as to what I am doing wrong would be very welcome :-)

It sounds like you haven't got a common ground between the arduino, multiplexer chip and the op amp.

I'm pretty sure I have actually...but I', about to sped another hour or so checking the circuit, so will post back here if I get it working as it should :-)

Oh...yes I had!

I had not connected the digital ground to anything - I thought it was internally connected to the psu ground, but on adding an explicit jumper to do the job all started working.

Thnaks :-)