I have a zero center meter and need to drive it??

Question

Ok I have a meter that has two leads and you can drive it bi-directionally so I know how to dive a meter one way:

outputValue = map(sensorValue, 0, 1023, 0, 255); // scale for analog out
analogWrite(analogMeterPin, outputValue); // write the analog out value

But I dont know how to drive it both positive and negative. Sound like fun any body have any ideas

Thanks for the help ~~ Cris H.

Oh BTW I could use a DPDT relay and drive it from a digital output..lol

vsluiter · Accepted Answer

I think the simplest would be to use two PWM outputs and 'drive' your meter differentially. If the meter should be in the center, drive both outputs half-scale (127 for Arduino), if it needs to go one way, you can drop one voltage and increase the other, for the other direction you invert this. I'm not at home in Arduino programming, but I guess this should kind of do the trick (analog in value 512 will be center): outputValuePos = map(sensorValue, 0, 1023, 0, 255); // scale for analog out, positive
outputValueNeg = map(sensorValue, 0, 1023, 255, 0); // scale for analog out, negative (notice change of output w.r. to positive)
analogWrite(analogMeterPinPos, outputValuePos); // write the analog out value for postitive pin
analogWrite(analogMeterPinNeg, outputValueNeg); // write the analog out value for postitive pin This should work for a meter that is suited for +/- your Arduino output voltage. If the needle hits the max, you can either adjust the scaling in software, or add a series resistor with the meter.

mcb1 · Answer

Cristina

My suggestion would be to use an Hbridge style approach.

One pin dictates the direction (polarity across the load) and the other PWM for the amount using your analogWrite.

I beats the clunky relay ....

mark

Robert Peter Oakes · Answer

Marks idea would work well, nice feedback.

Also, you scaling is quite simple and could be quicker simply by dividing by 4 eg: outputValue = sensorValue/4 ; there are even quicker ways but that's for later