# Dropping a 75V power supply to power an Arduino Mega

I'm looking to power an Arduino Mega using this IPC-5 power supply from Teknic since I will have a free port (the other powers a servo). I would like to use this extra port to power my Arduino rather than draw power from another source. The problem is that this is 75V coming out which would eat up the Arduino.

Is it as simple as hooking up a resistor in series with the Arduino to bring the voltage down to about 7V for the Arduino? If that's the case, then how can I determine the unknowns to find the appropriate resistor?

Correct me if I'm wrong, but if I apply Ohm's Law and Kirchhoff's Rules, I can set up this relationship: 75V = IR + 7V. Can I make an assumption for the current to solve for the resistance?

This is my first real Arduino project, so my knowledge of many things that y'all may consider common knowledge is lacking.

The short answer is NO, you can't do that. Consider the size of the resistor needed to dissipate all that wattage and the fact that the current is not stable so it is practically impossible.

What you need is a DC to DC converter.

• Thanks for your answer! I believe this is the solution to my problem. Jul 8 at 14:41

Is it as simple as hooking up a resistor in series with the Arduino to bring the voltage down to about 7V for the Arduino?

No, it certainly is not.

Can I make an assumption for the current to solve for the resistance?

No, you cannot. You never assume anything in electronics without a very very good reason.

You require a suitably rated voltage regulator (a switching DC/DC regulator for those kind of voltages) to convert the voltage properly.

• Are there any options out there for a 75V to 7-12V drop? My initial search is telling me that this drop is huge. Jul 8 at 13:46
• Yes, there are options out there. Here's an example of 75v to 5v: distrelec.de/en/…
– Majenko
Jul 8 at 14:10