Hello!

For an Arduino project I am putting together a DC-DC converter to get the required voltages.

As input I am using a lab power supply that provides +10V, 0V, -10V.
Since it is easy to mix up the polarity I would like to build a simple reverse polarity protection and output a safe to use +-10V, which is then further stepped down to +5V.

I read the following 2 articles on reverse polarity protection (http://www.instructables.com/id/Reverse-Polarity-Protection-Circuits/, http://qsysociety.org/qsywp/2010/12/diy-how-to-use-a-diode-to-provide-reverse-polarity-protection/) and decided my best bet might be a diode in paralell.

I am however unsure how to wire it for a +-10V power source. Is the following schematics the right way to do this?

Thank you!

 

Yup, but I expect that your lab supply has a current limit so you might not need the fuses.

 

Increase your lab power supply to 10.6V on both rails and install correctly orientated diodes in both rails?

 

Yup, but I expect that your lab supply has a current limit so you might not need the fuses.

Oh, yes you are right about that.

Increase your lab power supply to 10.6V on both rails and install correctly orientated diodes in both rails?

Yes, that is how I first intended it. But I thought it would be easier for future reference to just note: "provide 10V" to the input instead of "10.6V" so I preffered the solution without the voltage drop.
Is there any other advantage of doing it your suggested way other than not destroying a fuse in case of reversed polarity?

 

I'm not sure how much current you can get from the -10 Vout?
If you want to connect the fuse then considering the current of 7805 is Imax 1A, and considering the arduino needs probably less then 100mA, so you can
using a smaller current as 100mA~500mA, if the rated current of fuse is too high then it won't help for protection.

 

I'm not sure how much current you can get from the -10Vout?
If you want to connect the fuse then considering the current of 7805 is Imax 1A, and considering the arduino needs probably less then 100mA, so you can
using a smaller current as 100mA~500mA, if the rated current of fuse is too high then it won't help for protection.

Ok, thanks - I'll keep that in mind. I have a couple of shields and several modules hooked up on the Arduino so I'll need to make a current estimate.

The -10Vout is only needed for creating an analog +-10V signal used as input for an AC servo motor controller.

 

I've never been a big fan of dumping a dead short across the external power source as a way to protect the local circuit from reverse polarity. Seems like an extreme approach based on a potentially serious assumption. There is another way.

10 V is enough to fully enhance a power MOSFET. The bigger the FET, the lower the Rdson and consequent voltage drop. A 10 milliohm FET would drop 0.01 V, barely measureable (accurately) with a standard DVM. 1 n-channel FET, 1 p-channel FET, 0 resistors.

Circuits (b) and (d) in this image.

ak

 

I also like the use of a MOSFET to protect against reverse polarity.
I requires only 1 part and acts as a near ideal diode.