Protecting the motor

[aniruddha]

Hi,
I am using a motor for a particular task. I want the motor to stop if their is heavy obstruction/retardation to its motion so as to protect it from damage.

( By the way I am assuming that it will be damaged if motion is attempted in such case, is that true? or does it just switch off if it receives such heavy obstruction )

The motor is a small DC motor with torque=2kN.
It has only two i/p wires across which a potential difference of 5V (or 12V) when applied causes the motor to run, (the polarity of potential deciding direction of motion i.e. clockwise/anticlockwise).

Pleeeeeeease do pitch-in your suggestions.
THANKS in advance.

[Ante]

You need a current limit circuit preferably adjustable. Or, you could use a PolySwitch to protect the motor.

[aniruddha]

You need a current limit circuit preferably adjustable. Or, you could use a PolySwitch to protect the motor.

What are they? Where do I connect them? The motor has only two wires coming out from it.

[Ante]

Please have a look here: http://circuitprotection.com/

[Fowkc]

The device you use will be put in series with the motor. When the motor is stopped/stalled, the current through it will increase. So your polyswitch or current limiting circuitry will trip the circuit if the currnet rises too high.

[aniruddha]

Thanks for your help guys, but a polyswitch aint feasible bcos .... actually it isn't available in the local market and ordering it from net isn't possible.

But the idea, you all suggested, of using the rise in current during overload to trigger a ckt. break and again close ckt. after certain delay is great. This I plan to put to use in some way.

Soooo......
I am thinking for building something transistorised in nature.
You must be knowing the principle of "FOLDBACK CURRENT LIMITING" usually used for overload protection in transistorised regulators.
Wellll......
I am thinking whether a similar circuit arrangement is possible over here ??

Right now, we are trying to design something on similar line....

Incase anyone knows where we might get such a circuit readymade .... it would be useful.
                            OR
If someone has an experience in building something of similar type they could help us with the ckt. design...... or atleast suggest the components.


Any suggestions ??

By the way we are thinking on the right line right

[Ante]

Perhaps you can get PTC resistors where you live; they act similar to the PolySwitch if you find a suitable value for your motor (not as good but it works)!
Fold back current limiting is not the best choice for a motor circuit, this will not trip the circuit and if the motor gets jammed it will fry in a while.

[aniruddha]

Thanks for suggestions and help.
Looking forward to implement them.

[spency]

Would a chopper circuit from a L298 provide protection from stall current draw?

[Ante]

No, at least not by itself.