# motor to hold a specific pressure against something

i have a robot that plays a drum set. i am very familiar with programming but i am learning the electronics as i go. i am not familiar with motor types. the last step is to control the opening and closing of a hi hat. so i need a motor to hold up about a couple pounds for potential long periods of time.

if i use a standard motor would it heat up adding voltage when it cant move? is there some other motor type that would be better? or can i apply less voltage to a standard motor without burning it out.

any ideas would be helpful for creating a consistent even amount of pressure for an extended period of time with out overheating.

Use a self-locking spindle drive.

taterking: so i need a motor to hold up about a couple pounds for potential long periods of time.

I suspect the behaviour at the end of the period of time will be just as important for choosing a motor. Can you describe that please.

Also the mechanical linkage between the motor and the load is a key element. Please post a diagram that illustrates it.

If you have a motor that is powerful enough so that the weight is easy for it then the motor won't come to any harm.

...R

I'd be thinking of a solenoid instead of a motor (closing/opening a hi hat is a small linear movement).

wvmarle: I'd be thinking of a solenoid instead of a motor (closing/opening a hi hat is a small linear movement).

same first thought.. then there is the possible interference by any AC in the area that has the music. I did a light box years ago for a small band. uses AC relays for the lights. the two problemsI see are speed and distance. to move at the correct speed, one needs power, to move the needed distance, more power. a simple motor, with a cam could lift it easily, however the diameter of the cam lobe would dictate the distance. seems like a larger motor. as for holding power, it is not needed. move to position, then remove power.

dave-in-nj:
a simple motor, with a cam could lift it easily, however the diameter of the cam lobe would dictate the distance. se to meems like a larger motor.

That starts to sound like a servo.

Which solution works best will also depend on the actual construction of the hi hat, the distance and force needed, etc.

wvmarle: That starts to sound like a servo.

Which solution works best will also depend on the actual construction of the hi hat, the distance and force needed, etc.

a servo in the hobby arena is heavily geared. very slow, but does have mechanical advantage, great for applications where small and slow is acceptable. the old saying that "when the only tool you have is a hammer.... everything looks like a nail" we used a cam on a stepper to push a momentary switch. only rotated 180 degrees. steppers we had... by the score. As an aside. 1,200 beates per minute is the record for humans beating a drum. 20Hz so, that would be the upper design limit. but, like a servo, a pair of switches could say up or down.

A DC motor runs at a minimum speed, and a gear box is required for slower or stronger moves, or for linear movement. Then a self-locking gear unit comes without special extra cost, so that a certain position can be maintained with the motor power off.

Just thinking.

If the device is to move up and down or some component of up and down, the motor will need to have constant applied a torque to counter the gravity component. This is where I'd use counter weights adjusted to allow the unit to stay in position with power off; the counter to the gravity component.

I'd use either piezo transducers or pendulous resolvers to detect and create any needed offsetting torques.

I might use a magnetice lock set to provide just enough friction to help 'hold' the powered device in place but allow for movement of the device; if needed.

To go all out, using AC servo motors would to a really great job but cost a whole lot of money.

thank you for the advice everyone. so i looked through that drawer that everyone has of unused arduino “stuff”. I had a small hobby servo that I haven’t played with yet. I was actually surprised at how strong this little thing is. the strength is almost enough. i may see about ordering one slightly larger for the final project but i think this is definatlly going to be my solution. I pry never would have though of using a servo without your advice. if anyone is not familiar with a hi hat. there is a pedal at the bottom. the pedal is attached by a small chain. as far as counter weights, this is allready built into the construction of a hi hat. there are springs in the main shaft to counter the weight of the cymbols. my intention now is to rig a servo to pull on a string attached to the chain at the bottom to utilize this. I think it will be that simple. thank you again

wvmarle: I'd be thinking of a solenoid instead of a motor (closing/opening a hi hat is a small linear movement).

Except that its very common for solenoids to not be rated for continuous operation, so picking the right one is important.

Shouldn't be too big an issue with a hi hat, as far as I know (not a drummer myself but worked with them a bit) they're usually closed for short periods of time only. Like several seconds.

As a drummer, I'd say just the opposite. The hats are usually just open briefly. Think tap-tap-tap-pssst-tap-tap-tap-pssst where the psssst is the brief open sound.

An energized solenoid to push the two cymbals apart while the top one is struck would be fine, unless you are also after some nuance where the hats be opened/closed in more intermediate stages is needed.

CrossRoads: As a drummer, I'd say just the opposite. The hats are usually just open briefly.

Ah, I remembered the wrong way around :-) OP asking for the motor to actively close it wasn't helping with my memory. Indeed in that case it'd be better to actively open the hi hats, let the spring keep them closed.

Or take out the spring that holds them open, let the solenoid open them, and let gravity drop them closed (vs stepping down on the foot pedal against the spring pressure).