Hi, I want to build something similar to an analog clock.
I never worked with servos before, so I'm trying to get an idea so I don't buy the wrong one.
Besides the rotation range, is there any other feature I should also look for?
You will struggle. Most servos have a smaller than 360 degree movement. The so called continuous servos can not be set to a specific angle.
You would be better off with a stepping motor.
Perhaps if you used a DC motor with a big gear reduction such as these
You could control the speed of the motor with PWM and if you had some sort of feedback (perhaps every revolution of the second hand it triggers a sensor) you could adjust the PWM to keep time.
...R
you could adjust the PWM to keep time.
At a guess I would say that you wound not have the resolution on the PWM to make that work.
using a very small motor, since you only need to move the hands, you could use a small stepper, resistors and output directly.
you do not need a stepper driver until you get up to higher speeds and more power. and even then, you could get by with using transistors.
if you want one motor, then you would need gears for each hand. if you want to control each hand, then you could use a motor on each.
Grumpy_Mike:
you could adjust the PWM to keep time.
At a guess I would say that you wound not have the resolution on the PWM to make that work.
You may be right, but I was assuming the OP would have the speed almost exactly correct with gears and would only need to adjust the speed by a few percent up or down to be exactly on time.
...R
Thank you guys, I can get this one here with my provider
http://www.emartee.com/product/41886/
Would it work?
Jay98:
28BYJ48 Stepper Motor 5V - emartee.comWould it work?
Those steppers aren't quite as precise as they should be (~4000 steps per revolution, but they tend to miss one or two each revolution). If you could add something to track your position once a revolution (optoreflector, hall effect) then you should have no problems using it for a clock.
Thank you.
A final question, is there any downside with the 5V ones?
12V model is out of stock.
The 5V will be easier to implement (no need for a 12V supply).
Hi again, what is the less amount of arduino pins I will need to control one of these?
Let me change the question....
what is the less amount of arduino pins I will need to control 4 of these?
There are many Threads discussing those motors.
As far as I know they are 5-wire steppers and people use ULN2003 drivers. I think they need 4 pins per motor.
If you get a 4-wire stepper you can uses (for example) the Easydriver stepper motor driver board which only needs 2 Arduino pins - but the total cost will probably be higher.
...R
Thanks, can I manage the 4 motors with a single shield?
Let me pose an idea: The precission of the clock is coming via the arduino (that has it's own clock -quartz one), so the DC motor (or steeper or any type that can be minimally feedback controlled) has just to (slowly) correct the position of the hands along -say- the following hour (you need a "1 hour lapse" sensor in the clock itself). Such a case, you increment(decerement) a little bit the speed every hour to adjust it to the "real time" (arduino one).
¿Is it feasible?
¿Is it feasible?
Yes.
Quote
¿Is it feasible?
Yes.
¿and reasonable?
Well, I'm not planning to do a clock, actually it has nothing to do with time, I guess I did a very poor explanation.
It's more like a tachometer.
Anyway, I will like to know how this motors work.
The servo I was planning to buy at the beginning only has 3 pins, 5v, gnd and the last one to control the speed, but these ones have 5.
I can't even realize how to wire them
I mentioned already that people use ULN2003 chips (not a shield) to drive those motors. And I mentioned that there are many Threads on the Forum about them. You do some of the research.
...R