Electronic Circuits and Projects Forum

hi Hesham,
I have realised you uses the word 'turn' for the digital servo motor.

A servo will only 'turn' , that is rotate, less than an angle of 300 degress or so, its not a stepper motor.

Build the 555 circuit shown in the link and test/learn from the servo control before you consider using the 16F818 PIC.

I already build it!!

Nothing happen nothing rotate.

First about my project: my instructor or advisor decided that we just need to go as far as we can because he say if we never have a deadline you will never keep pulling things.
He is not interested about the result of the competition. He is interested how far we go. How much we learn!

Second about 555 timer, I build servo driver for my ds8911 servo but nothing happen here are several question i need to ask.
Q1> How you know for P1 where is 1 2 or 3?? or 1 and 3 doesn't really matter? just the middle one matter

Q2> I am sure that i need higher frequency rating. The one I am using now is 50Hz. I think i need to come up with a new design for 555 to run my servo motor. As the tutorial mentioned at the end there are new bread of servo motor which are know as digital servo motor. These motor need higher frequency to operate. I operate my servo motor using function generator at 300Hz. But 300Hz is just a guess. Because time is critical now, I will go with 300Hz.
If you know how I can set the period using PIC16F818 it will be great.

For fun I just bought a PIC 16F877 it so big hehe 40 legs

Why not learn to use MPLABs built in simulator. Try to generate a 1.5ms wide pulse with a 20ms period. The stopwatch function is quite handy.

Thanks blue for replying,

I connect the wires again and Ya its working now. But its shaking (jittering) in the desire place. I am not sure what wrong.

When I used function generator to operator it. It operates, but the problem is I am confused which parameter I am suppose to change duty cycle or period? Look at the diagram to understand more.

When I kept the duty cycle at 50% it operates from 0 to 120 by changing the period from 1.6ms till 4.3ms.

But when i kept the duty cycle at 20% it change from 0 to 120degree by changing the period from 4.1ms till 10.9ms.

I am confused which paramerter to change duty cycle or period. Both work, but which one is better?

When the frequency is 500Hz i can change duty cycle from 21%-62% to have that interval.

Q2> I am using pulse in function generator and its working fine when I use square wave it going crazy or jittering. You know how I can produce pulse using PIC? Any ideas?

Thanks in advance

Stop fussing with the function generator and guessing at values. Servos have specific parameters if you want them to function.
Here's my advice
Write code for whatever PIC you plan on using in assembler that will output a 1.5ms pulse every 20ms to port RA0 and run it using the MPLAB simulator. Stop playing with stupid values you think might work and start following specifications. You are proceeding at a snails pace because you simply don't seem to follow advice.

I build this servo motor circuit

555 Servo Circuit - Mechatronics Wiki

When I read the signal using Oscillascope it was reading Fine AMP +5V OnTime 1.8ms for 2.2V Analog input.
When I connect my servo it started shaking around? Any ideas why it keep shaking?

Ya the frame rate is 23ms.

Any idea why it's shaking.

What's your frame rate? Did you read my post about digital servos and 555 drivers (October 28).

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