hi, i am new here. i am a 14 year old, who has a electrical engineer as a father, so he has all of the parts and toys for me to make just about anything! i have lots of books, and am quite good at basic electronics, and i wish to make this project.

i want to make an esc for a r/c car. not a toy one, but a porportional control one. i have made a "rig" with a pot, mosfets, batterypack, and motor. i have made it work, without frying anything. now, i need to find a way to CONTROL it using voltages. the voltages comming from the reciever vary in hundreths of volts. the voltage range is small, and i need something to convert this to control a much higher voltage. here is what i have out of the reciever : .42 - .24 voltage. i need that to control a voltage up to about 8.4 volts, porportionally.

thank you!!! please excuse my noobishness! :lol:

 

I assume the "receiver" is a radio receiver.

I also assume that the voltage coming out of it is an analogue signal in the range 0.24 ~ 0.42 Volt.

If these assumptions are correct, then what you need is an amplifier followed by a motor speed controller. The simplest controller would be simply a MOSFET.

Connect the amplified signal to the gate and it will cause the FET resistance to change and thus control the motor speed. You will also need to shift the level so that the voltage varies from 0 to 8.4V.

A more complex (but better) solution would be to use a switching controller with feedback. The controller applies pulses of 8.4V and, during the off period, uses the EMF generated by the motor (which is proportional to the motor speed) as the feedback signal thus making the speed control much better, eg. if the car goes up a hill, it will not slow down very much compared to with the simple solution.

Remember to protect the FET from back EMF with a diode.

__________________
Len

 

oh, well just hooking up a fet wouldnt be effective, cause it only puts out the recieved voltage. my father decided to sit with me and help me on this, and now i have a working esc! we used a 324 op amp to amplify the voltage, and put it to the fet, which i connected to the motor. thank you for the response. my projects problem has been solved, so there is little need for anymore postin. thank you!

 

You're welcome

__________________
Len