Does the RC transmitter control power consumption?

Question

This might be a little off topic, please be understanding.

In case of an RC car toy (specifically, for children) you can control the speed of the car via the transmitter. I am wondering, if I were to customize the transmitter and limit the maximum speed of the car, let's say, to half of the original, do I (or the kids) get to enjoy playing for double the time with the same batteries? (for the sake of simplicity, let's say that the throttle on the customized transmitter can only be pushed half way)

So does the transmitter control the power consumption of the RC car, or it's only a torque to rpm conversion?

Cheers, John

Answer 1

Yes, sort-of.

The speed controller switches the motor on and off in very rapid pulses, and the width of these pulses (and the width of the 'off' period) is controlled by the throttle. It's so fast that the motor just sees it as a varying voltage.

So if you cut a piece of card and stuck it on the transmitter to prevent full throttle being used, the speed controller would only run the motor at partial power. The car would accelerate more slowly, have a lower top speed and the battery should last longer. It should break less when you crash too.

However, voltage supplied to the motor is only part of the story. The current drawn from the battery is what's actually important, as battery capacity is measured in Amp-Hours (i.e. a 1AH battery can supply 1 amp for an hour, or 2 amps for half an hour, etc). The current decreases as the motor speed increases. A motor running at full throttle with no load will spin quickly but draw little current but the same motor struggling through grass will be running more slowly and drawing more power.

So if you want longer run time, drive on a smoother, lower-grip surface or change gear ratio to a lower gear so the motor can reach its top speed with less power. Or buy some extra batteries...

Answer 2

I'm not sure that I fully understand your question, so sorry if this answer is wrong.

The transmitter controls how fast the motor goes and also makes the servos on the plane move. If you have the motor at maximum the whole time then you will run out of battery pretty fast. Keeping the motor at full for too long is also a good way to damage electronics. If you keep the throttle lower, the motor will use less electricity in a given amount of time but it will also provide less thrust. As the thrust decreases, the plane will go slower and have reduced climbing ability. If the plane goes too slow then it won't be able generate enough lift to stay in the air. I believe that the transmitter throttle channel changes what percentage of power available goes to the motor. This last part is speculation and is probably partly wrong. It is loosely based on my experience with RC cars.