Hey all,
I'm trying to control a 7.2V powered servo with a 5V Arduino PWM output. However, it doesn't seem to be working when I power the servo with 7.2V but does work when it is powered via 5V.
Is the 2.2V difference between the servo voltage and the control voltage too much? Would reducing the servo voltage to 6V work or am I stuck with 5V?
I want to power the servo with a higher voltage than 5V so that I can take advantage of the increased servo speed at those voltages.
Thanks!
I'm guessing that when you use the 7.2V supply, you don't connect the servo/power -ve to the Arduino ground.....
Not sure what you mean... I'm powering the arduino with the same 7.2V supply. The servo ground and the arduino ground are both connected to the 7.2V batteries ground.
At 7.2 volts the servo will pull a lot more current than at 5V. You shouldn't
be powering the Arduino and Servo from the same supply, that's the cause of
95% of servo problems. Servos pull a lot of current in bursts, thing 1A or so
per small servo, 2A for larger servos. If that causes the supply to droop and
the supply powers the Arduino it will reset.
If really unlucky the servo might put inductive spikes onto its supply rail and
cause damage to logic circuitry.
Even with the on board 5V regulator?
It's definitely not reseting the arduino. The servo doesn't even appear to attempt to move or activate in the slightest.
Advancer:
Not sure what you mean... I'm powering the arduino with the same 7.2V supply.
Ah, well you didn't say that, so yes the the grounds would be together automatically.
But just to get it totally clear, best you post a schematic. Two in fact: the working one (servo on Arduino 5V if I understand) and the non-working one (servo on 7.2V). Code won't hurt, either.
Any ideas?
I'd try putting a small signal diode between the 7.2v battery and the RAW(?) input on the board, and a large capacitor between the board power bus and ground. The capacitor will help keep the board from experiencing a possible low voltage when the servo moves.
The servo doesn't even attempt to move and I'm able to freely move the servo arm; this is why I think it's an issue with the control signal not the servo pulling too much juice and resetting the arduino.
I also forgot to mention the servo is not under load at this point.
The control signal is a logic signal, it should work at 5V regardless. 95% of servo
issues are bad power...
Well, then you probably have faulty wiring if you run the same code as is used with the working servo. Also, is the 7.2v servo a digital servo or some non typical hobby servo?
Turns out the battery was almost dead. It looked OK with my multimeter and had enough juice to power the Arduino but when I connected it to my battery charger, it indicated it wasn't pushing any amps.
I charged it up and everything seems to be working as intended now.
Thanks for the help everyone!
