I'm working on a school project where I plan to use 3 MG90S servos and 1 MG995 servo. I haven’t purchased them yet, but I want to make sure my power supply will be sufficient. I’m using an Arduino UNO R3 to upload the code, but I know it can only supply 5V, which isn’t enough to power all the servos. Based on my calculations, the total voltage needed might be around 24V, especially since each servo will also be connected to a rotational sensor. What kind of power supply or setup should I use to safely and effectively power the entire circuit?
The servos run on 5V and you connect all four power leads to a 5V supply.
What you need to calculate is the total current in Amps (A) that you need for all three servos.
An UNO can only supply 20ma (0.020a) per pin, the MG90S servo uses 100-250mA when moving.
What power supply could I use?
You can use any 4.8V to 6V power supply that is easily capable of handling the total stall current for all the servos. For the SG-90 budget 1 Ampere per servo, for MG995 budget 2.5 A/servo, so about six Amperes minimum for your project.
Battery packs for RC vehicles are a good choice, and don't forget to connect all the grounds.
Remember that servos briefly draw the stall current every time they start moving.