servo Posted August 10, 2011 Report Share Posted August 10, 2011 Hey, all. I've run into a real problem with my control circuit. The circuit is simple enough. I am designing a controller for a servovalve that looks something like this.It's a 10VDC signal with negligible current. The equipment can handle a couple of extra volts, so the 12VDC won't hurt anything. The frustrating thing is, it works in one direction, but when I flip the switch to reverse the direction of the command, it stops working unless I turn the pot all the way and then I get a large current draw. I don't understand at all why this is happening. Why does it work in one direction, but not the other? When I hook up a power supply directly to the switch, it works fine, but with the regulator and pot in there it starts acting funny. Help please! I've been stumped for two days and I need to get this figured out.I should say that I forgot to ground the regulator in the schematic. It is grounded on the breadboard, though. Also, I've run it through Multisim and it works just as it should, so does that just mean there's a problem with the way I have it set up on the board? Quote Link to comment Share on other sites More sharing options...
servo Posted August 11, 2011 Author Report Share Posted August 11, 2011 I'll attach a picture of my setup. Hopefully it helps. This is the first circuit I've ever designed. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted August 11, 2011 Report Share Posted August 11, 2011 Have you checked that the Command - isn't permanently connected to the same ground as the 12V regulator? Quote Link to comment Share on other sites More sharing options...
servo Posted August 11, 2011 Author Report Share Posted August 11, 2011 It is connected to the same ground, more or less. The command ground is connected directly to the negative lead on the power supply, and the regulator is connected to the negative bus on the board, which is then connected to the negative lead on the power supply. Quote Link to comment Share on other sites More sharing options...
Hero999 Posted August 12, 2011 Report Share Posted August 12, 2011 If the command is connected to the same 0V rail as the regulator, ther wil be a short circuit on the 12V supply when the switch conects it to +12V. Quote Link to comment Share on other sites More sharing options...
servo Posted August 16, 2011 Author Report Share Posted August 16, 2011 so where do I ground it? Quote Link to comment Share on other sites More sharing options...
Hero999 Posted August 16, 2011 Report Share Posted August 16, 2011 You don't need to ground the 0V rail. Quote Link to comment Share on other sites More sharing options...
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