Radio control of PWM motor speed?

[gregster]

Guys can anybody help, ive found a PWM circuit online that works well for speed control of a dc motor, is it possible to replace the speed pot with the output from a radio control receiver and therefore control the motor using the transmitter? any ideas would be much appreciated, cheers

 

[sam2]

How big is the motor? Voltage , current? There are alot of electronic speed controls out there for R/C. The largest ones I know of will handle 40 amps /20 volts, but I am sure there are much larger.
If the motor is alot larger you could always control the pot with a servo.

 

[Sceadwian]

Supply a link or post a schematic of the circuit you're using for the motor controller. Little to nothing can be suggested if you can't provide a schematic.

 

[gregster]

Thanks for the replies guys, here's a link to the circuit i'm using http://solorb.com/elect/pwm/pwm1/

What i wanted to do is replace the VR1 pot that controls the speed with the output from one of the channels of my receiver. I realise that there will need to be another circuit to convert the receiver output to a suitable format, just don't have a clue what it should be. I know it'd be easier just to use an ESC but I'm interested to see if there's a way of doing it myself. feel free to say if i'm asking the impossible!!!

 

[Russlk]

Assuming that the speed pot is only providing a voltage to the PWM control, a frequency to voltage IC would work.

 

[Nigel Goodwin]

Thanks for the replies guys, here's a link to the circuit i'm using http://solorb.com/elect/pwm/pwm1/

What i wanted to do is replace the VR1 pot that controls the speed with the output from one of the channels of my receiver. I realise that there will need to be another circuit to convert the receiver output to a suitable format, just don't have a clue what it should be. I know it'd be easier just to use an ESC but I'm interested to see if there's a way of doing it myself. feel free to say if i'm asking the impossible!!!

It's by no means impossible, just making it more complicated than it needs to be - you need to convert the pulsewidth to a DC voltage (0-12V), then feed that to the comparator input.

A frequency to voltage IC would be a nice idea, except the frequency does'nt change, just the pulse width.

 

[kinjalgp]

Thanks for the replies guys, here's a link to the circuit i'm using http://solorb.com/elect/pwm/pwm1/

What i wanted to do is replace the VR1 pot that controls the speed with the output from one of the channels of my receiver. I realise that there will need to be another circuit to convert the receiver output to a suitable format, just don't have a clue what it should be. I know it'd be easier just to use an ESC but I'm interested to see if there's a way of doing it myself. feel free to say if i'm asking the impossible!!!

What type of output does your receiver give?

 

[gregster]

It's a Futaba FM receiver, don't know if that means the output is FM as well?
Is there an IC i could use that will take the receiver output in at one end and throw a pulse width type signal out the other? that'd save me having to faff with two different circuits!!

 

[Nigel Goodwin]

You can do it with a PIC, which would be the modern method - but years ago ETI Magazine did just such an ESC. They actually did two different versions, to show different approaches, one analogue, and one digital - both gave similar results.

The servo outputs from the Futaba should be the standard variable 1.5mS pulses every 20mS.

 

[gregster]

Thanks Nigel, i'd like to learn more about PICs actually, i already looked at some of your tutorial pages!! forgive my ignorance but would i have to buy a specific type and then find the correct software or is a PIC a generic chip that can be programmed to suit any need?

 

[Nigel Goodwin]

Thanks Nigel, i'd like to learn more about PICs actually, i already looked at some of your tutorial pages!! forgive my ignorance but would i have to buy a specific type and then find the correct software or is a PIC a generic chip that can be programmed to suit any need?

PIC is a type of micro-controller from MicroChip, there are many other types available as well, but PIC's are the most popular ones. There are a number of websites that have radio control projects using them.

Here's one example:

 

[gregster]

Thanks very much Nigel, and all the other guys who helped out, i'm off to learn about PICs!!!
Incidentally Nigel, are those circuits you mentioned from ETI magazine still knocking about? I'd be very interested to see them even though the PIC route is obviously best for my problem.

 

[Nigel Goodwin]

Thanks very much Nigel, and all the other guys who helped out, i'm off to learn about PICs!!!
Incidentally Nigel, are those circuits you mentioned from ETI magazine still knocking about? I'd be very interested to see them even though the PIC route is obviously best for my problem.

I can't even remember what year they were - but it was a LONG time ago, I 'might' still have the issue somewhere, but I have thrown a lot of older magazines out (I had a large collection, back to the 1950's).

 

[gregster]

Well please don't spend hours rooting through on my behalf!!!! though if you should happen across them i'd love to see em
Thanks again for your help, the muddy waters are clearing, bloody slowly mind!!!