Power Supply Monitor

Hello. I have a variable sypply 3-20v 3a and i want to convert it with a timer. i will use an arduino nano with max471 to monitor voltage,current and time. I thought to use a transistor bd243 to on the V+ line of my power supply to switch off when the time is done. is that possible? The circuit will be like a classic NPN switch.

Thanks in advance

It would help if you drew us a circuit diagram you’re proposing.

i attatched a screenshot of the circuit that problems me. Can arduino drive the bc243? and it will be able to turn off the power to my load?

With an NPN transistor, the load should be between PUS+ and the collector, with the emitter connected to PUS-.

You should also have a resistor between the Arduino and the base to limit the current from the Arduino pin.
If Vbe of the transistor is, say 0.7V (similar to one diode), and you want to limit the Arduino current to 20mA, then:
(5V - 0.7)/0.02A = 215 ohm. So a 220 ohm resistor would work well.

Make sure PSU- connects to the Arduino Gnd as well so there is a common reference point.

So something like this and it will work. Thanks

Edit: I forgot to edit the resistor value from 10k to 220ohm. I will change it
Annotation 2020-05-11 155727.png

Annotation 2020-05-11 155727.png