Current flow controller for DC Motors

[mackrackit]

The motor will draw the amps needed. So if the driver circuit will handle the starting amps you are OK.

When the motor is running, less amps are required, the amps will drop. The greater the load the greater the amps. An amp meter can be used for feed back to tell how much of a load is on the motor.

I do not think the extra circuitry is needed.

[mikebar]

The motor will draw the amps needed. So if the driver circuit will handle the starting amps you are OK.

When the motor is running, less amps are required, the amps will drop. The greater the load the greater the amps. An amp meter can be used for feed back to tell how much of a load is on the motor.

I do not think the extra circuitry is needed.

Thank you very much mackrackit for the answer.
Actually, what I'm looking for it is some "automatic sensor" that does not allow more than 5A at 24V for the motor. This kind of circuitry could also reveal if the motor's shat it is locked.
I wish to avoid the use of fuses, because one the fuse is blown it need somebody that replace it...
Any idea?

[mackrackit]

What about an automobile/truck circuit breaker. They reset on their own and normally will handle a bit more amps than rated for a short time.

But if the shaft is locked then you do not want it to keep trying? So a latching relay tied in with the circuit breaker might do the trick.

[mikebar]

What about an automobile/truck circuit breaker. They reset on their own and normally will handle a bit more amps than rated for a short time.

But if the shaft is locked then you do not want it to keep trying? So a latching relay tied in with the circuit breaker might do the trick.

Uhmmm..
It could work.
I was looking for some more sophisticated solution (like transistors that regulate the current flow right to the thereshold)...

[skimask]

Uhmmm..
It could work.
I was looking for some more sophisticated solution (like transistors that regulate the current flow right to the thereshold)...

It's called 'foldback' in a regulator circuit.
http://en.wikipedia.org/wiki/Foldbac..._supply_design)
Totally useless link, but it might get you started...

EDIT:
http://www.national.com/appinfo/power/files/f4.pdf
Better link...

[Acetronics2]

Thank you very much mackrackit for the answer.
Actually, what I'm looking for it is some "automatic sensor" that does not allow more than 5A at 24V for the motor. This kind of circuitry could also reveal if the motor's shat it is locked.
I wish to avoid the use of fuses, because one the fuse is blown it need somebody that replace it...
Any idea?

did you look at Raychem RUE Polyswitches ...

much better than your PIC ... as Dave raised !!!

lol

I think Microchip has a similar App Note about servomotor ... just take the relevant part ...

Alain

[mikebar]

Thank you guys.
It is a starting point.
I'll post some other questions and when I reach the final result, I'll post the schematics.

Thank you, for now.

[sayzer]

If your PIC has comparator, then you can use it to detect current as you wish.
The example below shows the use of an external comparator, but if your PIC has an internal one then you are good to go.


<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=2892&d=1223533980" >
________________

[mikebar]

If your PIC has comparator, then you can use it to detect current as you wish.
The example below shows the use of an external comparator, but if your PIC has an internal one then you are good to go.


<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=2892&d=1223533980" >
________________

Thank you Sayzer, for the hint.
To be honest, I've not clearly understood if GH1 and GH2 are 2 different pins or whatelse. Any suggestions for the filter capacitanze (R and C values) that goes to the comparator? I think to drive the motor with max 5KHz PWM wave. Voltage 24Volts, maximum allowed current to the motor 5A.
Some suggestions also for a good logic level MOSFET for this kind of motor and the name for a fast recovery diodes?

Thank you a lot.

[sayzer]

mike,

This is for reference.

You can play with the values and come up with the right ones much faster then using formulas.

---------OR------------
You can use analog reading to speed up and down the motor for the time you need.
You need a resistor for detecting motor current anyway.

If your analog reading is high, then slow down the motor, and if low then speed up the motor.
You just do it for 2 seconds as you need.