Variable Power Supply Connection

Hello all!

Question I’m not sure if this is the right place but I’m going to try!

My question is: I’ve built a variable AC-DC power supply and I’d like to hook up the arduino to receive power from it to power the Arduino Uno somewhere along the way. Goal is to use it for various things within the power supply enclosure.

I’ve attached a pic of the schematics and parts list. The rest of the circuit works fine, prototype worked great. Just need to plan out a point of contact for Arduino power before I order the PCB.

Thanks all for any and all help/suggestions!

Grash_Sharptooth:
My question is: I've built a variable AC-DC power supply and I'd like to hook up the arduino to receive power from it to power the Arduino Uno somewhere along the way. Goal is to use it for various things within the power supply enclosure.

8V would be, as I see it, "ideal". The supply output should terminate in a DC plug ("2.1mm") suitable for the Arduino barrel jack. That should result trouble-free use.

If I understand correctly, you're going to use this as a variable output voltage power supply, to supply various things, but also want to power the Arduino from it.

If so, RunawayPancake misunderstood your post. If not, I misunderstood your post. :smiley:

And the Arduino will monitor the output voltage, among other things.
So the problem is how to derive a supply for the Arduino.

Since I assume that at times the output might be adjusted too low for the Arduino, and possibly even as low as 1.25V, (the absolute minimum that you can get out of this circuit), you will need another separate supply for the Arduino, taken from the rectifier before the LM350, then separately regulated to either about 8V as suggested by RunawayPancake, or 5V for a direct connection to the Arduino's 5V rail.
The best thing for this is possibly a small switching DC-DC converter module if the rectified DC voltage is 12V or higher, to keep power dissipation to a minimum. (You'll already have enough problems with dissipation, using a linear regulator for your power supply.)

You don't mention the transformer's voltage rating. Could you tell us that please?
And out of interest, what voltage and current range do you want from the power supply?

As mentioned, you might have some serious power dissipation problems, especially when the output voltage is low but the current is high.

I'd reduce the value of the mains fuse a lot, a 50VA transformer will cook and catch fire if it
has 12A of mains flowing through it.

Add a power resistor before the smoothing cap to reduce current spikes and increase the
conduction angle.

You'll need a hefty pass transistor on a heatsink if you are providing 3A output, most regulators
have info in the datasheet for how to drive a pass transistor.