Cordless drills

[alinas1]

If you don't give any voltage to a cordless drill, it won't turn. No matter how much you will try to turn it (with your hand) you won't succeed. How and why does this happen?

[Addison4300]

The drill is spun by electro-magnets and locks in place when not given any power if I am correct.

[baumgartensam]

My understanding is that many have a mechanical brake that engages when the drill is stopped. Some newer drills also have electric brakes that slow down the chuck using the energy from the deceleration of the chuck (I forget exactly how they work). The E-brakes don't continue braking after the drill stops where as the mechanical brakes do. Look on youtube for some videos with people disassembling drills.

[GeeTwo]

Here's an often-cited paper on converting a DeWalt clutch for FRC purposes.

[Tom Line]

Cordless drills have anti-backdrive pins built into them. They are small metal cylinders that shift when the drill head attempts to rotate when the motor is not rotating.

In fact, the window motors you have use a similar system:

http://www.chiefdelphi.com/media/papers/download/3449

Page 6 of the nothing-but-dewalts whitepaper linked above has a picture showing the anti-backdrive pins.