Electronics > Beginners

Control Duty cycle with (logic gates,Flip flop etc)

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christos:
Hello!
Is there any way I can control the DC% with flip flops or gates. at 100hz?
I want to control a servo motor using Logic gates and flip flops.

Thank you!

Ian.M:
Not easily with pure logic gates and flipflops, however if you allow the use of monostables available in most logic IC families, its pretty easy.  e.g. see fig 13 of http://www.ti.com/lit/an/sdla006a/sdla006a.pdf

retrolefty:

--- Quote from: christos on December 08, 2018, 01:06:50 pm ---Hello!
Is there any way I can control the DC% with flip flops or gates. at 100hz?
I want to control a servo motor using Logic gates and flip flops.

Thank you!

--- End quote ---

 Well I have seen a zillion 555 timer chip circuits used to operate hobby type servos that require a 1 to 2 millisec variable pulse width at a 20-25 msec frame rate. Many RC servo testers on Ebay.

Benta:
christos, not in an easy way. You'll need to define what kind of resolution your PWM needs. An analog PWM theoretically has infinite resolution, with a digital you risk servo jitter.

A solution using programmable counters is possible, but will be large.

christos:
Thank you for the replies!

I'm currently trying to make a block diagram in Quartus to program the FPGA . I need to make at least 1 servo move

The frequency that the servo will work is at 50Hz (20ms) with duty cycle from 1ms to 2 ms (servo model SG90)
I made a frequency divider from 50MHz to 50Hz but I stuck there, I tried to use a comparator but no luck there too.
Thats why I'm trying to figure another way to make it work


and I cant use a 555 timer or the 74L123!

Thank you again!

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