Can I do this with an Arduino?,

Hello, Thanks for taking the time to read this. I am new to Arduino, have basic electronics skills and no programming skills but am a fast learner. Here is what I need to do. I need to output a bipolar voltage of -5 to +5vdc very low amperage is perfect. I would like to do this via the servo outputs of the Mega as i have about 15 items I need to control. I was thinking servo center would = 0V. LEft = -5V Right = +5V. Is this possible to do with Arduino? Are there other options? I am using this to build gauges to interface to FSX in my flightsim. Also my motion base, the motor amplifiers except the aforementioned voltages to drive the motion system. I have ordered my Mega and am looking for expierenced help in this project. If anyone is close to Indianapolis,IN i am willing to pay for the help in set-up and programming. Thanks, Rob

I need to output a bipolar voltage of -5 to +5vdc very low amperage is perfect.

The arduino will not do this directly it will only output 0 or 5V. To get this to happen you will need a -5V power supply and also a PNP transistor on each output. If you want three voltage levels (+5 - 0 -5) then you need two pins and a few more components.

I was thinking servo center would = 0V. LEft = -5V Right = +5V.

No the servo library produce a pulse position modulated output, there is no easy way to translate this to voltage levels.

I have a PIC16 that takes a servo PWM input and outputs a 0-5Vdc signal. I guess I could drive it with the servo out of the Arduino but not sure how to change my output from the interface I made. I have a schematic if it would help. I also have a +/-15Vdc pwr supply to use so that is handled. Also, the output must be variable, not just 3 voltages. So it could swing from +5 to -5 to control the gauge or motion system. Another option would be driving a DAC using the Arduino but that as well out of my skill set. Again, willing to compensate someome for helping out here.
Thanks for the info.
Rob

I have a schematic if it would help.

Schematics always help.

I also have a +/-15Vdc pwr supply to use so that is handled.

Well not quite you still have to produce a regulated -5V to switch to.

Also, the output must be variable, not just 3 voltages.

So now you say!!! That changes everything. You want to use the PWM outputs, feed that to a PNP transistor switching between +5 and -5, and then the output needs to be filtered with an RC circuit.

Try this circuit.

See this link for a discussion about the values of the RC filter:-
http://www.thebox.myzen.co.uk/Tutorial/PWM.html

Variable Voltage.pdf (21.3 KB)

Here is a schematic of the servo pulse to 0-5vdc out converter i use. works well but i need it to swing to negative volts. If a little PIC16 can do this why not an Arduino?

egtadapt.jpg

Grumpy_Mike:
Try this circuit.

See this link for a discussion about the values of the RC filter:-
PWM

Thanks Mike, That circuit looks familiar to this one.

ifcv1.jpg

That circuit looks familiar to this one.

Well it’s doing the same thing, I just made that one up for you.
Your circuit is missing the smoothing on the PWM.

Seems to me this would be easier to do with an analog output. If the analog output varies from 0 - 5V, couldn't you amplify that to be 0V - 10V and shift it with a reference voltage.

I couldn't build that circuit if you paid me, but it has to be easier than manipulating PWM.

Seems to me this would be easier to do with an analog output.

Yes but the arduino hasn't got one.

couldn't you amplify that to be 0V - 10V and shift it with a reference voltage.

Well that would be even more complexity than just the simple A/D output that you can't build. And remember that the OP wants several of these.

but it has to be easier than manipulating PWM.

No it definitely is not. We are talking about one transistor a capacitor and two resistors. You are talking about one or more D/A chips interfaced through either SPI or I2C and two operational amplifiers. How is that easier?

Good point, so far I've only dealt with the digital pins on the Arduino, and didn't realize the analog ports were input only. Makes sense though now that I think about it.