Hello. I am new to Arduino and my first project (other than blinking lights) is connecting a high torque servo to a door to open and close it. I am trying to figure out the best way to power the servo.
It is a 7.2v 40kg/cm servo. It should be strong enough to open the door if powered properly.
Can I power the arduino atmega 2560 with 9v adapter and then take the power from the Vin pin to the servo? I'm guessing I need to limit the 9v coming out of the pin, but not sure how to do this.
You will damage the servo if you power it from 9V. Also, motors introduce noise into shared power supplies and can cause erratic behavior or even damage the Arduino.
You need either a separate step-down regulator (this one should be fine), or much better, a separate 5-6V power supply capable of supplying a couple of amperes. If the latter, connect the two power supply grounds together.
Thanks! I found a regulated power supply that is adjustable between 3v and 15v. It has options for 6v and 7.5v but nothing in between. How would I get the most out of the servo (7.2v) with that set up?
Maximum ratings are given for a reason. The only safe choice is 6V.
Furthermore the power supply MUST be capable of supplying enough current for the servo -- minimum 1 ampere, and probably more.
Is there a way to use some step down like a resistor or voltage regulator?
6 volts will probably give close to the maximum torque. You could put a diode (be sure it can handle the current) in line with the 7.5 - that would drop the voltage a smidge so it's below the maximum allowable. You don't want to run at the max voltage anyway, a small miscalculation or external condition could result in an overvoltage that may fry your motor!
Oh, and just to be a bit of a pendant, and while still not correct, use kgcm, not kg/cm for torque. (It really should be Ncm. Here's a link.)
How many amps does your servo need?
If your power supply cannot provide enough amps the servo will not have the torque you expect and the power supply may be overloaded and damaged.
...R
I can not find any information for that. I purchased on amazon and they do not specify the amps. I have a power supply that can do 2A so I'm hoping that is enough.
Is there a way to use some step down like a resistor or voltage regulator?
Read reply #1.
The one you specified only has options for 6v or 7.5, I would like 7.2 which I can not seem to find.
It is a BAD IDEA to run anything at the maximum rated voltage.
Jkittle1209,
You are misunderstanding what a rated voltage means. In this case it means that if you give your motor anything over 7.2 volts, it will likely burn out. Use 6 volts (or follow my previous recommendation if you want a bit more voltage.) Do not try to trim a power supply to EXACTLY 7.2 volts.
Thanks for the help!