Hello

I have a PLC module which can unly accept unipolar VDC(0-5VDC, 0-10VDC). Few of my sensors are +/- 10 VDC output and I need to feed this to the PLC module. How do I convert a bipolar signal to unipolar? Any ideas appreciated.

Thanks

 

hi,
Look at this recent thread on the same topic.

http://www.electro-tech-online.com/m...ease-help.html

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Eric
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Hi I looked at your circuit in the posting. Can I use a low power Quad Op-Amp for this purpose? Like LM 124 or something? So that I can have 2 channels from one chip. Also Supply voltage must be 8V? or Can I have +/-15? I was thinking of changing it to +/-10 input to 0-10 o/p. 5V clamping diode is necessary? Or can I live without it as long as my i/p will not exceed. Now when you mentioned 2.5Vref in the reference ckt, are you thinking of another resistor for the divider? Please let me know.

Thanks

 

hi,
You could use a quad OPA with a +/-10V supply, you must clamp the Vout so that it dosn't exceed +5V to the MCU adc input.
Also you will have to clamp the same voltage so that it cannot go negative.

Thats why I am showing two OPA's, the 2nd OPA has only a single +8V [or higher with a clamp] supply.
A very low forward drop diode should be able to clamp the output so that it cannot go negative.

The +2.Vref supply resistor is chosen to suit say about 5mA thru the reference from an available +Vsupply.

What did you think about other members idea's regarding just using potential dividers?

.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

As in the other thread, it all depends on the relative impedances.

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Thanks for your respose. What do you think of this circuit? Is it OK? Only thing it doesnt have is the attenuator portion.

http://www.daycounter.com/Circuits/O...-Shifter.phtml

One more question, Can I hook up my input signal common to the circuit common? Which will be the OP-AMP supply common too;

Thanks

 

The Daycounter circuit uses a modern rail-to-rail opamp, not an old LM324 or LM358. The LM324 and LM358 outputs go as high as 1.2V less than their positive supply voltage. Their inputs don't work if they are higher than 1.5V less than their positive supply voltage.

If you don't connect the commons together then nothing will work.

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