how to convert PWM to voltage

[Donahue]

hello, i am looking for some help on a problem for my job. i am looking for a way to convert the PWM signal from receiver into an analog 0-5V signal to be used with an industral motor controller. i am not very familiar with most of the components google says to use. can someone point me in the right direction?

[heyok]

What you want to do is build yourself an Integrator circuit. That will convert the average of the "on time" into a voltage.

signal -->resistor---> +cap- --->Ground

Then you will need to run it into an op amp or something to shift the voltage to the level you want.

Take the voltage from the positive end of the cap. Hope that gets you started.

[JohnRobHolmes]

Alternatively a servo could turn a POT if you weren't so savvy as to build such a thing. The voltage shifting of the integrator would be the tricky part.

[heyok]

Originally Posted by JohnRobHolmes

Alternatively a servo could turn a POT if you weren't so savvy as to build such a thing. The voltage shifting of the integrator would be the tricky part.

What a great solution! Sometimes it is so easy to overlook the obvious.

(I'm not being sarcastic)

Thanks!

[JohnRobHolmes]

I've had to build them before for such a task. The internal servo feedback POT can be used for the signal as well if the industrial controller 5v rail is used to power the servo and RX. Positive and negative power the system, and signal is tapped off the center of the POT. The tricky part is getting it to throw far enough to max out the feedback POT on both ends of travel, a radio with EPAs helps greatly. It is simple to get the signal to line up otherwise, if the signal is reversed biased the channel can simply be reversed.

The only downside is that the servo transit time will dictate throttle response, but that isn't always a big deal.


What industrial controller you using Donahue? I probably have experience with it, and if I don't I will know somebody that does.

[moes670]

I think this will do what you want.

http://www.bpesolutions.com/bpemanua....to.analog.pdf

Working on a simular project here at work. We are using a different module however. It requires some programming knowledge and some resistors and transistors to boost and condition the signals. A bit more involved than the link above. The plus side is we will be able to control 4-6 channels with this module at about the same cost as the one in the link.

Can't remember the name of it right now but will come to me soon

[Donahue]

Originally Posted by JohnRobHolmes

...What industrial controller you using Donahue? I probably have experience with it, and if I don't I will know somebody that does.

we use PG Drives S-Drive and I-Drive controllers for our machines. 70 and 140 amp in the 24V variety.

http://www.pgdt.com/products/i-drive/index.html

the servo to the pot idea is going to be a last resort.