Servo trouble

If a servo is  not powered it will not resist rotational forces applied to it. So in your words it will fail

there may be some models of servos with locking mechanism but I am not aware of them

a motor can also be so some what braked by shorting it's winding which will cause it to self lock

this could be done with a relay, great care will be needed to not apply power while the relay is closed of course

Peter Oakes wrote:

a motor can also be so some what braked by shorting it's winding which will cause it to self lock

how to do it?

if yo take a simple motor, a small one out of a toy or something

with nothing connected to the motor power pins, try turning the motor, it should move relatively easily

now put a short across the power pins of the motor (No power or anything, just a short), with the short in place, not try to turn the motor

with the short it should be far more difficult or even impossible without significant force to move it, this is because the motor is generating a reverse EMF that ends up opposing the direction of rotation.

this happens with pretty much any motor that has a magnet and coil arrangement

Peter,

how would I know which type of motor is inside. Plus how to do it?

Wong,

I'm using a servo built, don't want to break the servo. Even if I onpen to attach a worm gear, not sure out to do it and gear ratio. I want one with the exact torque as this one(If hand build)

-Radio Control Planes, Helicopters, Cars, Boats, FPV and Quadcopters - Hobbyking

Peter,

how would I know which type of motor is inside. Plus how to do it?

Wong,

I'm using a servo built, don't want to break the servo. Even if I onpen to attach a worm gear, not sure out to do it and gear ratio. I want one with the exact torque as this one(If hand build)

-Radio Control Planes, Helicopters, Cars, Boats, FPV and Quadcopters - Hobbyking

There are many worm gear actuators that produce torque in excess of 500 kg-cm.

There are several modules that will convert standard DC motors into RC servo motors. such as this (RC Power Servo) or (http://www.robot-r-us.com/motor-controller/pololu-simple-high-power-motor-controller-18v25.html)

There are lots of DC gearmotors with worm gears that can be converted to servo motors.

There are many servo systems that outperform RC servos.

There are many motor controllers that may suit your requirements.

We need to know range of motion, size, weight, speed and cost requirements as well as torque to make any kind of suitable suggestion.

I don't want a controller: just a servo

size-  40*40(4.7 max0)

range of motion- stationery i.e. 0

weight- 78gs{ 100 g max(the lesser the better)}

speed-useless( because range of motion- stationery i.e. 0)

cost- 70${80$ max(the lesser the better)}

torque-40kg{no lesser(38kg min with adjustments)}

Hope this is helpful

What about winch servos?

-Radio Control Planes, Helicopters, Cars, Boats, FPV and Quadcopters - Hobbyking

I don't quite get why a servo is needed if no motion is needed.

A fixed bracket could do the job described.

If you want to apply a variable torque - a servo is probably not the best way.

Any linear actuator could supply holding "torque" - many can do this without power.

Greetings Royston, There's something your not telling us. Is the servo only being used to stop movement or is it being used to control the movement.  For example move the load to a position ans hold it there.

Without knowing what it's being used for it difficult for us to help you design this thing you are building. For some reason you are forced to use servos when other devices may be more efficient.

You have some very good ideas here. Maybe we don't understand your requirements.  A little clarification of what it is your trying to make would be extremely helpful.

-Steve