Make a servo go counter-clockwise for 5 rotations.

Hello. This is my first post so please don't get mad at me for any typos or errors.

Anyway, I am currently making a project with an Arduino Uno, a Servo, and a DS3231 RTC. I have constructed it and coded it to a point were the RTC activates the Servo at a specific time. It then spins it in a clockwise rotation for five spins. I am stuck at the point where I want it to go counter clockwise at another selected time for five spins. The farthest I got with this is going 180 degrees counter-clockwise.

I just need code, and it needs to spin counter-clockwise for five spins. The board I'm using is the Arduino Uno.

NoNqmeCrqckerz2: Hello. This is my first post so please don't get mad at me for any typos or errors.

Anyway, I am currently making a project with an Arduino Uno, a Servo, and a DS3231 RTC. I have constructed it and coded it to a point were the RTC activates the Servo at a specific time. It then spins it in a clockwise rotation for five spins. I am stuck at the point where I want it to go counter clockwise at another selected time for five spins. The farthest I got with this is going 180 degrees counter-clockwise.

I just need code, and it needs to spin counter-clockwise for five spins. The board I'm using is the Arduino Uno.

Some servos can't do a whole rotation. Can you post a link to the one you are using?

I am using the micro Servo SG90 Tower Pro. I am sure these can do a full rotation.

NoNqmeCrqckerz2: I am using the micro Servo SG90 Tower Pro. I am sure these can do a full rotation.

The second sentence of the SG90 data sheet says "Servo can rotate approximately 180 degrees (90 in each direction)".

ChrisTenone: "Servo can rotate approximately 180 degrees (90 in each direction)".

That's strange. I got it to go 360 degrees in one direction.

Huh. Sure, out of spec stuff happens all the time with electro-mechanical devices. But it's always an anomaly, and never guaranteed. They make continuous rotation servo motors, but perhaps you really need a stepper, or a gear-motor with encoder.

Perhaps if you explained your ideas, someone could help from a similar experience. Advances happen in baby steps.

Thanks for your help! I have used a stepper motor before but its not strong for my blind opener project. I will get another better stepper motor if it works! :)

Either way - you need to determine where 'zero' is, then get told when the output shaft completes each revolution.

A Stepper is convenient, but position still needs to be calibrated every now & then. Draws current when stopped under load.

DC motor is also fine, but also needs to know where it is. Encoders or shaft position sensors/switches can help.

(These both become closed-loop 'servo's in the strictest sense of the word.)

If you have a continuous rotation servo then it just behaves like a DC motor. You can control the direction and the speed but not the position.

As has already been said regular servos can move through about 180 degrees with position control.

You can also get sail-winch servos that can rotate 3 full revolutions with position control (and I think you can get some that can do 6 revs).

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So, should I go with a Stepper Motor, a DC motor, or continue with a Servo but with a different type?

For opening and closing a blind I would use a simple geared DC motor with limit switches for the top and bottom.

And a continuous rotation servo is probably the simplest form of geared DC motor to use as all the electronics are in a neat box that is easy to attach to things and you can use the Arduino Servo library to control it.

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You can buy a special ”winch” servo used on model sailboats. It can usually do about 10 turns. If you use servo.writeMicroseconds() you would get about 1/100th of a turn resolution (values between 1000 and 2000 microseconds).

Ok thanks! I'll try out a DC motor and a winch Servo. Thanks for your help! :)

DO check the specs beforehand to make sure they have enough torque to lift your blinds. Preferably at least double the minimum torque needed.

johnwasser: You can buy a special ”winch” servo used on model sailboats. It can usually do about 10 turns.

The most I have seen is 6 turns and most of them only do 3 turns. Position control would be very imprecise if spread over 10 turns. And the sheets on a full sized sailboat are managed +/- 1 inch.

...R