Hello, I am new to electronics and I would like to know how much current my circuit draws. I've used a multimeter before, but I am now I am stuck. I have a circuit on a breadboard powered by a Li-Po battery. I have about 7 components attached to an Arduino Nano. 6 components are connected to the 5 V pin and 1 is connected to the 3.3 V pin. How would I go about measuring the current draw in this circuit when I have components connected to two different power pins. Should I unplug the 3.3 V device and measure from the 5 V pin and then unplug all the 5 V devices and measure from the 3.3 V pin and add these two currents? I just have a lot of wires and don't want to unplug everything. Thank you.
What's the purpose of the measurement, to see how long the battery will last maybe?
Correct me if I'm wrong, but it sounds as if the Nano is powered by the battery to Vin, and the components run off the Nano pins? In that case you need to break the circuit from the battery to the Nano and measure that current.
Hey there, thanks for the response. The 3.7 V battery is actually plugged into a 5 V step up voltage regulator which is directly connected to the 5 V pin of the nano. Vin on the nano is not used. Should I still measure current like you suggested - Break the circuit in between the battery and the voltage regulator? or should I break the circuit along the 5 V line? and yes, I am doing this to see how long my battery last.
I think you should break the circuit from the battery to the regulator, since it's the current from the battery you will divide into its mAh capacity to arrive at time.
Since the voltage out of the regulator differs from the input (the battery voltage), so too will the current for a given power consumption so the current out of the regulator is no help in calculating the battery life.
Just be super-careful because the ammeter is a short circuit. If you connect it directly across the battery (in parallel) you'll blow the fuse in your muitimeter, or if you connect it at the "wrong place" you can short-out and damage your circuit.
I assume your meter has a separate connection for measuring current, so as soon as you are done, switch it back to Volts/Ohms.
Seconded - leaving a multimeter setup for current is a sin - don't do it!
A friend of mine used one of those little red DMMs from Harboring Fright Tools, despite my warnings to the contrary. He had been using it on his car, then was troubleshooting his 240V dryer outlet.
He'd left the leads plugged into the 10A current measuring sockets. The DMM exploded into a lot of pieces. He was quite luck that he wasn't holding it, and that the leads did not burn through instead as it would have given him some terrible injuries.
Ouch... Yes the 10A range is often unfused in cheap/nasty meters...
Also, the 10A range in many inexpensive meters is limited to a short time and a low duty cycle.
I mean REALLY low duty cycle. This Extech is limited to 15 seconds max every 15 minutes!
https://www.lowes.com/pd/Extech-Digital-Up-to-600-Volt-Multimeter/999990508
You have to look at the meter itself, see between the 10A and COM jacks:
