Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Constant frequency variable duty cycle PWM

Status
Not open for further replies.

baddabaddabing

New Member
Hi,

I'm doing a university project (mechanical not electrical engineering, hence my lack of knowledge) which requires an analogue signal (from LabVIEW) to be converted into a PWM signal to drive a servo motor.

The servo requires a frequency of 50Hz with the duty cycle controlled by the LabVIEW output (ranging from 1ms to 2ms). I was intending to use a 555 timer, but I can't find a configuration that lets me obtain such a low duty cycle but keep the frequency constant.

Could anyone point me in the right direction for building such a circuit or at least tell me if I'm approaching this the wrong way? I had looked at using op-amps as an alternative but I've found the same problem.

Thanks a bunch,

Stuart
 

Leftyretro

New Member
50 hz with a 1-2msec duty sounds just like PPM used to control model R/C servos. Pehaps you sould search for R/C servo testing circuits to get a idea of how to proceed.
 

crutschow

Well-Known Member
Most Helpful Member
You use one timer to generate 50Hz pulses. This triggers a second timer configured as a one-shot whose pulse length varies according to the control signal (voltage-controlled one-shot or monostable vibrator).
 

KMoffett

Well-Known Member
What crutschwo said.

**broken link removed**

Look for "Voltage Controlled Pulse Width Oscillator" there.

Ken
 
Status
Not open for further replies.

Latest threads

Top