Sensors

[AlexanderTheOK]

Originally Posted by platypus122597

Hey guys! One more question: I know on talons there is a brake mode and a coast mode. What's the difference and what do they do? Thanks!

This one is a bit more obscure and interesting.

A motor is basically a backwards generator. (and vice versa) You can observe this fact by plugging two nxt motors into eachother and spinning one by hand. Trippy as it is, the second motor will turn. (Because the first motor is generating electricity and sending it to the second one)

But wait, when a motor controller gives voltage to the motor, the motor spins. This means it starts working like a generator and sending voltage at the motor. This is called back voltage.

Current flows only when there is a voltage difference, so if nothing is stopping the motor (theres no load), it speeds up until it basically sends back almost the same voltage, and electrons almost stop flowing. Motors are designed around the idea that they are moving when they are being sent power. When they arent moving (stalled), theres no backvoltage, and the difference is massive.

Now why does this matter for the coast vs break settings? In coast mode it leaves the circuit of the motor controller as is. In coast mode the controller isnt sending any voltage, but the motor (by virtue of inertia) is moving, and thus generating electricity. Since you dont want electricity making the voltage higher than normal the circuit is just kind of cut (someone fact check me on that one because I'm not ENTIRELY sure this is how motor controllers deal with backvoltage) electrons are shoved into the wire, but they cant go anywhere, so once again, theres little difference between what is "being sent to the motor" (by the wire that is charged by the motor) and what the motor is sending.

In brake mode it shorts the motor, connecting the positive to negative. Now the electrons CAN move, directly, through a low resistance circuit. The voltage difference is now large causing more resistance on the motor, stopping it quicker.

I will edit this as people tell me I'm wrong, which is likely to happen.