PWM to 0-5V and more...

[Gibelgab]

Hi Guys.

I need some help.

I have a 48V/200A brushless motor controller and the motor speed is regulated by a 5-10Kohm potmeter that is turned by a model rc servo. I'm using 100% of the servo movement.
Now I want to get rid of this mechanical solution by using a PWM to 0-5V converter connected to the rc receiver.
BUT... I also need a relais to be activated when the voltage is 0-2,5V (adjustable) from the above mentioned converter.
Can anybody help me trough this? I can make the circuit board and the soldering, but that's all.

 

[indulis]

Are you looking to use the servo PWM signal to drive the motor controller instead of having the PWM signal control the servo which "turns" the pot?

 

[Gibelgab]

Yes. And additional I need the adjustabel relais function. Now I'm using a microswitch on the servo arm.

 

[indulis]

You would have to first find out what the duty cycle range is of the signal that drives the servo. Then, what is the voltage range of the pot that controls the motor.

 

[Gibelgab]

The pulsewidth is 1ms for servo position 0% to 2ms for servo position 100%.
The voltage range out of the pot is 0-5V.

There is also a 12V power supply if it can be used for the converter.

I think there is a good description of the signal from the receiver **broken link removed**, but first: I can't find the components in the last diagram before chapter 3 (the article is from 2004) and second: The relais thing is still missing.

 

[indulis]

Which components can't you find? There is really nothing special there... a small MOSFET, almost anyone will do that has a small Rds on and the opamp needs to have a low bias current (probably any FET input opamp would work).

 

[blueroomelectronics]

This controller will convert RC servo to PWM but at 35A is too small for your 9,600W motor.
Sabertooth 2X25 regenerative dual motor driver

Another solution would be a microcontroller with a D/A or digital pot connected to the existing motor controller. As a bonus it could do the 2.5v output switch in firmware.

 

[indulis]

It's the rating of his controller, not his motor.

 

[Nigel Goodwin]

An easy way is to use a PIC, it can easily read the incoming signal, set the output voltage accordingly (using either PWM or a D2A), and switch a relay as required.

 

[Gibelgab]

Ok. Then I use a HEF4049BP instead of the CD4049B. But I don't understand the "U4" and "U5" in the diagram. Is it the same component? And right underneath the "RxPulse" there is a circle with + and - inside, is it a capacitor? If yes, I can't see which type. Anyway, I can't se the type on the rest of the capacitors.

2N7002 and 1N4148 are ok, but I'm not comfy about the LT1012. Can I use a LT1793ACS8#PBF instead?

And how about the adjustable relais function?

Indulis! I see your hobby is flying. The project here is for this one.

 

[Gibelgab]

Nigel! Thanks for your reply. I have been looking at your links and I think it's even more complicated than the traditional way without programming. No programming, please. The hardware alone is tough enough for me!

 

[Gibelgab]

Bill! Thank for your reply, but that part I have in control. I need some stuff to control the controller!