Let's Make Robots!

Can i control a servo with a 555 timer?

Hi,

I would like to sweep a servo back and forth, and theres no point on using the arduino for this, and thats all i have at the moment, so if i supply 0v to the yellow wire on the servo(signal) and then supply it with 5v, then 0, then 5v again.... would it sweep the servo? or does it have to be modulated?

 

ty

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i want to make a robot with one servo, and it can drive in any direction, i it will have to be swept back and forth to go on a stratight line. i dont want to make it sweep manually, must be automatic.

Normally a servo has a range of motion of about 180 degrees, but they can be modified for continuous rotation. If you are hoping to use a servo as the motor to move your robot around, that may be your best approach. There are walk-throughs on this site and others on how to perform this modification.

With a single continous rotation servo driving your robot, it will be easy to go backward or forward. However, if you want to be able to turn, another mechanism is needed. The most common approach in robotics is to have two matched motors (or servos). One drives the left side and the other drives the right side. You can adjust the speed and direction of the motors to allow your robot to turn. Another approach would be to use one motor or servo to drive your wheels forward and backward, while a normal servo is used to drive a wheel that steers.

Do you have something else in mind that will allow a back and forth sweeping motion to drive your robot in any direction? If so, I'd love to hear your idea. I'm having trouble visualizing how it would work.

i havent got the idea in any digital thing yet, its a draft on a paper, i'll scan it when my scanner is working :P

 

 basically the servo rests at 90º it has 30º of dead angle(meaning it wont move any wheel, must have this to be able to turn, so at 75º it starts moving the left wheel forwards, and at 105º it moves the right wheel forwards, all wheels can only drive forwards, i just use two conveir belts(rubber bands :P) two printer gears(same size) and two ONEWAY bearings(from nitro cars pull starts, i still havent got these, well, just one, they are a bit overpriced.

when its done, i will post how i did it, it will just follow light, and maybe, MAYBE a line, it works in my head, i have to try doing it in lego or something first, i'm gonna use a small carson servo, pulls about 1.2 kilos/cm.

 

i thought about using a continuous rotation servo for this, but this way is much more of a challenge :P

 

as for the 555's i found out one of them was burned, i did manage to sweep the servo by sweeping a pot(by hand) i think i will use an attiny, if all else fails.

Sometimes you have to let them do it the hard way.  We all have our own way of learning, and that sometimes involves banging your head against the desk for awhile. Yes, using a picaxe or arduino would be easier, but this way a person would learn exactly the how and why servos work. Remember, this is supposed to be fun and educational.

Mech

However, only the last (double 555) circuit on that page could be capable of sweeping the servo back and forth - the rest all hold the servo at a particular position.

Perhaps you could give us some more info on what it is that you're trying to acheive amando? Is this just a circuit for testing servos, or is it for an actual project?

Did you bother to read the circuit description? In the first circuit, the 100k pot adjusts the output pulse from 0.9 to 2.1 ms, sweeping the servo with a single 555.  The second circuit also adjusts the pulse using a single 555 and a 74121. 

Your tone is not necessary. I was under the impression that amando was looking for a circuit to sweep the servo by itself, without the need to constantly adjust a manual pot, which is why I went on to ask what the actual application of this circuit would be.

The second circuit might as well use 2 555 ICs, since the 74121 is just another type of multivibrator - a second 555, or a 556 in place of the 2 555s would also do the job.

His description suggested a manual switching of the wire to "pulse" a servo, adjusting a pot to sweep is hardly a stretch.

 

It is an assumption to state the amando was planning on manually switching the wire, just as I had assumed he wanted an automated solution from reading the post title, "Can i control a servo with a 555 timer?".