Servo jitters then stops working

Hey all,

I'm using a RedBoard to try to activate a back-and-forth motion of 2 servo motors (SG90s) with a fingerprint scanner (GT-521F32). Everything runs fine the first 2 times I place my finger on the scanner, but after the second time the motor starts jittering. When I place my finger on the scanner a third time, the jittering stops, but the motor does not turn. As soon as I remove my finger, the jittering continues.

I checked the voltage being delivered to each component with a multimeter and everything seems fine on that front. I've tried connecting the RedBoard to the wall as well as USB. I've also tested each component individually with sample codes I've found online, and all components work perfectly fine by themselves.

Here's a pastebin of the code: FPS w/ 2 servos - Pastebin.com

Thanks in advance!

Usually such behaviour is caused by insufficient power. The servos will almost certainly need a separate power supply. Don't forget to connect the grounds.

Power problems +1.

+2. A good rule of thumb is to budget 1 Ampere per servo. Some take a lot more, though.

Help us help you.
Get a pen and paper. Draw a wiring diagram, including details about your power source and how it is distributed to the servos and other components. Take a picture of the drawing. Post the picture here.

Thank you guys for the quick replies.

At first everything was connected in series. I attached a separate power supply for the two servos as shown in the picture, but now they are just jittering uncontrollably as soon as I upload the code. Am I supplying too much voltage now? I drew up what I think is happening.

Thanks again

Why are the servos wired up in series? They should each have 6 volts if that is what they are rated at.

Sorry, I meant to say (and draw) parallel.

This is my first project, sorry for any stupid errors.

You need a common ground between the servos and the arduino.
What is your power source for the servos? (voltage, current capacity)

common.png