C40S = C40R

[Shiva]

Hi Everyone,

I'm new here and I need help from everyone.

As the topic, me and my friends bought this Servo Motor (C40R) and tested few days ago. But no matter what we gave, either PWM (followed from User Manual given) or giving direct pulse, we still unable to make the motor to rotate in anticlockwise direction (just able to make it rotate in clockwise).

My servo is having 3 wires, red (power), black (ground) and white (pulse). It's an unmodified version.

I would appreciate any advices or suggestions, thanks in advanced.

[ober]

What is the pulse width you are giving to the servo?

The sample program provided used 20MHz Crystal, are you using the same speed of crystal? Can you capture a picture of your setup and show it here like other forumer did? Have you download the sample program into the PIC? Can you measure the pulses with an Oscilloscope to verify the pulse width?

[Shiva]

What is the pulse width you are giving to the servo?

I gave the pulse as the User's Manual instruction

The sample program provided used 20MHz Crystal, are you using the same speed of crystal?

Yes, I am

Can you measure the pulses with an Oscilloscope to verify the pulse width?

Yes, I could, but I haven't taken it yet. But this was what happened.
When I gave 1ms, it turned to right,
When I increased it to 1.5ms, instead of moving to center, it slowed down the speed of the rotation
When I increased it again to 2ms, instead of moving to opposite direction, it started to rotate the same way as when I gave 1ms.

[aurora]

sound like a modified servo for continuous rotation with the potentiometer screw up (faulty).

or

the code is buggy?

[ober]

Yes, I could, but I haven't taken it yet. But this was what happened.
When I gave 1ms, it turned to right,
When I increased it to 1.5ms, instead of moving to center, it slowed down the speed of the rotation
When I increased it again to 2ms, instead of moving to opposite direction, it started to rotate the same way as when I gave 1ms.

Do you mean that the servo keep rotating? Because from what you described it sounded like the servo motor keep rotating at certain direction instead of the other way. Let say if you provide 1ms, you say it turned right, does it stop after some time? It should stop at a position and maintain there as long as the 1ms is there.

Anyway, if the problem still occur, please go to our support tab (top bar of Cytron front page), fill in your problem and submit, our support team will follow up with you.

[Shiva]

Sorry for didn't mention it previously.

I have 2 versions, Modified and Unmodified. Both are having the same problems. I can't use unmodified servo and keeps on giving them pulse, cos the rotation will keeps on going and I'm afraid will spoil the motor.

Therefore, what I could do for unmodified is I gave 1ms, it turned, and then I increased the duty cycle, it still happens the same and I directly stop the testing.

[ober]

Sorry for didn't mention it previously.

I have 2 versions, Modified and Unmodified. Both are having the same problems. I can't use unmodified servo and keeps on giving them pulse, cos the rotation will keeps on going and I'm afraid will spoil the motor.

Therefore, what I could do for unmodified is I gave 1ms, it turned, and then I increased the duty cycle, it still happens the same and I directly stop the testing.

Shiva, please be clear on what you want to ask as this will lead forumer to different recommendation and solution. Cytron only sell C36 for modified servo (except for special request) and the modified servo from Cytron only have 2 wires. In your case, since you mentioned that the servo you have is C40 and have 3 wires, so we will assume you are using standard servo.

But you also mention that it keep rotating in right direction, a standard servo cannot rotate in a direction 360 degree or continuously, the boundary is only 180 degree. That is the reason Aurora and I ask you whether is modified or unmodified servo. I have checked the sample source code provided in product page. The sample source code actually generate pulses with the pulse width of 0.7ms for 50 times and jump to generate pulses width of 2.0ms for another 50 times. It will then keep looping between these 2 routines to generate pulses of 0.7ms and 2.0ms. If everything works nicely and connection is correct, the servo should will rotate clockwise, stop a while , rotate anti clockwise, stop a while and repeat until you stop the PIC or power off.

If you are using the sample source code, how do you give 1 ms and change in the middle of program running? Because the sample code is generating 0.7ms and 2.0ms pulses only. If you have edited the sample source code, have you compile it and load the new hex code to your PIC board with a programmer? Another concern is about giving pulses, not pulse. From your statement, you said you give 1ms, is the pulse being generated continuously? You need to generate continuous pulse, thus it come the "pulses".

I would really recommend you to check the pulses from PIC to servo signal pin with an oscilloscope.

You can check the unmodified servo by turning the servo horn clock wise or anti clock wise when it is unpowered. A standard servo have boundary for 180 degree only. It should have a stopper to limit the rotation. Of course don't use force to rotate until you break the stopper.

[aurora]

if the servo is unmodified, then it's probably the code. You probably use a cumulative function instead of direct fuction.

Standard servo can stand stall current for few seconds. It happen to me all the time when i accidentally sent an out of range pulse. When it hits the limit, the servo will vibrate. It should be fine as long as you disconnect it quickly. Try use a lower voltage, i.e. 4.8v.

Normal servo, 1ms is about 45deg, 2ms is about 135deg, while 0.7ms is 0deg, 2.3ms is 180deg.

[robosang]

aurora, yup correct. But nowadays, there are too many type of RC servo in the market with different spec, the standard become non standard.

Most of people like to use RC servo, but do not understand the operation condition and concept of controlling it. I have been using Futaba and Sanwa years back, C36 too (not much). I did spoil a few because of wrong control signal and cause it to stall at the limit too long and finally break the internal driver and some the mechanical stopper. Yet, I like to use it.