Looking for Ready made stand alone DIGITAL PID.

Jamie · 2009-07-01T18:14:47+00:00

As it said. We need to replace some analog PID boards due to supply andside effects the existing ones have. The PID code that comes in digital drives and process controllersare pretty much what we're looking for how ever, we only need justa design that allows a input ref, reference feed back and a outputto drive what ever device. This device should have it's own mini LCD interface to set thevalues or at least a computer hook up to do so. It should have the standard Proportional Gain, Integral andderivative components to set the values. Also, having an option to select unipolar and bipolar outputis a plus!.. I know there are various analog boards out there already thatdo this how ever, We have found that they seem to exhibit sideeffects and cause self oscillation under some conditions. In the digital varieties, I have found this not to be a problembecause it's being done via software and thus these effects are not visible. I have already made a few using a AVR/ATMega that employ the ADC inputs and we simply buffer the output into a PWM filter and op-amp. These units are programmed via a serial connection for the params. How ever, my employer wants to buy units that are ready made so thatreplacements can be had with out depending on in-house designs. I have looked and I can't find a unit that has a build on LCD displaywith a simple interface to do this.. We do have a SSD out board key pad unit that does do this function for us along with some other little nifty things how ever, it appears that this unit is no longer available. Any idea's?

Jul 01, 2009 22 Replies

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linnix 17 years ago

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'll

Single 4V supply. Source of 2N7002 and negative side of capacitor at virtual ground (minus input of LMV358). Drain of 2N7002 and positive of cap to LMV358 output. Gate of 2N7002 to groung with/without 10K resistor.

Tried some 2N7000 (TO-92). Same result.

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Joerg 17 years ago

If I understand it right than this sounds ok. You just can't ever go reverse because then the FET's body diode will kick in.

Something is wrong there. But hard to say from far away.

Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.

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JosephKK 17 years ago

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Please post a circuit fragment in LTspice. This 2n7002 circuit behavior is memorably odd. Be very careful to identify real ground and virtual ground differently.

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