![dcmotor[1].jpg](https://i.imgur.com/nCgfGB4.jpg "dcmotor[1].jpg")
So DC motors are pretty interesting, and they are indeed inductors. So that must surely mean that if the magnet inside has stopped moving some kind of resistance should be changing, as such does that mean that it's possible to tell if a motor has stalled?
I want to try and set up a smart motor, that will stop pumping current through when current spikes.
Everything you've written is correct, and there have been motor driver ICs that detect stalls like this for the last forty years or so.
Something to keep in mind that current will also spike when the motor is going from stopped to spinning. Your logic needs to ignore current spikes for a short time after switching the motor on.
>>909235
Sensorless 3-phase BLDC motor controllers use the effect to advance the commutation phase.
>>909238
thank anon.
could you direct me to a good website that i could read more about this?
>>909240
>3-phase BLDC
Kinda looks like a Stepper motor. Cool
>>909241
Not that guy, but I believe this is called "inrush current protection". A google search like pic related seems to have dropped some good results, maybe have a dig through these?
>>909247
thanks anon, that's real useful
![motor-image-002[1].png](https://i.imgur.com/OryZciX.png "motor-image-002[1].png")
OP Here.
After doing some reading and looking up.
I have found that during a stall, the current shoots up real high, obviously really bad. but as such, this is a readable current draw. So that means i could read the current with a microcontroller. If anything. From other readings, i could use a voltage divider, to read the voltage as it fluxuates. But i feel that this still could be inaccurate as, hypothetically speaking, perhaps the battery isn't even affected by the current draw.
What do you anons think?
Am i on the right track
![lowside[1].jpg](https://i.imgur.com/LFcJQmy.jpg "lowside[1].jpg")
So here's a solution. This schematic is what you'll want. just use a shunt/sense resistor, like this. The Op-amp is not necessarily required, but it can help
>>909254
Don't you need a flyback diode?
>>909251
Current creates magnetic field. Field in motor opposes field of spindle. I can't remember the terms. But when it runs the current is working to turn the spindle. As torque opposing the motor increases the motor does more work to overcome this.
Maybe its even possible to pass the stall current by actively driving the motor in reverse from the spindle?
But anyway yes watch the current.
>>909354
A DC motor doesn't produce a pulse of back EMF when you cut the power like a basic inductor does. You only need the snubber diode in a situation where someone could spin the motor in reverse by hand; turning it into a generator.
>>909403
>A DC motor doesn't produce a pulse of back EMF when you cut the power like a basic inductor does
Shit, did not know that. Why not?
>>909435
That's exactly it. The generated current doesn't become a problem unless its moving in the opposite direction, which would only happen if the motor was running in the opposite direction.
>>909251
That's exactly the graph you need. You could also name the y-axis "current" and it would still fit, as the current is proportional to torque.
So, you measure the current, via a shunt or a Hall sensor, (there are diveces available that connect tirectly to an arduino). If the current value gets too high, the motor is stalled, that's it.
Basically, you can model a motor like this:
You have the resistance of the coils (which turn), and the voltage applied. These two values define the stall current. As the motor turns, a reverse voltage is generated inside, which opposes the applied voltage. So the effective voltage the coil windings see is the applied voltage minus the generated voltage. The faster the motor spins, the bigger the generated voltage is, and the smaller the effective voltage is as a result. As the coild resistance stays the same, the current gets smaller as well. If the motor spins fast without load, the generated voltage is almost as big as the applied voltage, this is why the current is very small now.
If you want things to be very simple, with the least amount of electronics possible, google "polyswitch" or "polyfuse". These things are basically self-resetting fuses. They heat up when too much current passes, and the heat increases their resistance like a lot, so that only very little current passes and nothing burns. To reset them, take away the voltage for a while to cool, and then they're good again.
I thought this was exactly what safeguards like circuit breakers were for. current goes too high, circuit turns off to protect cables. Couldn't you just wire in a low rated breaker closer to the motor with a delay to allow for start up current?
