Servo on off control setup

This is the wired up configuration for the servo test I was doing. The setup includes the following

• Arduino pro mini 3.3@8Mhz
• ULN2803 Darlington array(8ch) with 2 channels being used.
• Joystick analog input device
• 9g servo(w/ 1/4 in barbed valve attached)
• 1S 3.7v Lipo 500mah

In attempting to keep power consumption as low as possible, I needed to disable the signal and disconnect the servo from the main power rail. Unfortunately I didn't have any smaller darlington array transistors(TO220 or similar like a TIP21) or  didn't have enough other single transistors to do the job, so I utilized the ULN2803 which I had several of lying around.

This worked perfectly(aside from the area it takes up) bringing the current down from 100ma+ at servo idle, down to 20ma.

 The code is fairly simple at the moment for this setup with the primary things being turning off the Darlington array and detaching the servo when no signal isn't needed. If you don't detach( myservo.detach() ) the servo it will try to feed off of this signal to power the servo(though not being able to power it through the low current signal line). You will also hear a constant wining from the setup.