Good morning. I'm designing a lawn mower robot with Arduino. I decided to use a brushless motor to drive the blade. During a test too much grass has blocked the blade and the engine caught fire. I wanted to ask if there is a way to control the current drawn by the motor in such a way that if this exceeds a certain level imposed the Arduino code to turn off the engine or to do something in order to avoid further damage. Possibly there were other solutions are open to suggestions. Thanks in advance.
You use current sensors to detect overload. What sort of motor and driver are you using?
I use a 1000 KV brushless motor one of those for drones with a 30 A esc.
So if I connect a 30A ACS712 current sensor to the motor and I write in the code when the current exceeds 25 A (for example) the brushless motor is turned off and then on again after a certain time it should work? Or there might be better ways?
Thanks
No, current sensor in the supply to the ESC is where to put it. They you only need one, not three.
A current sensor 30 A is sufficient? Given that motor could absorb a peak of 30 A
Well its your motor - measure what current it needs for normal running (which will take a little cleverness
devising a method to do this as multimeters go upto 10A typically). Remember the wiring in a high
current system makes a ready-build shunt resistor...
Thank you so much. I try to measure the current absorbed by the motor and then I set accordingly. once I found the maximum current consumption is enough for me to write in the Arduino sketch that a thick reached a certain "threshold current" the motor is turned off or is better put to the circuit of physical protection? (Fuses or something)
What is ready-build shunt resistor?
You already have fuse to stop the wiring melting/catching fire don't you?
No I had not put. I thought that the engines were more resistant and that within the ESC, there was already a protection.
How much current the fuse should withstand? (How should I put it?)
RC brushless motors will fry at the drop of a hat, they are run well past standard "continuous rating"
conditions. One cubic inch of motor is expected to handle upto 100's of watts, of which 10% of more is
heat into the windings.
The fuse protects the wiring, not the load.
So how do I keep the engine operating in a field in which I am sure you do not burn? if it encounters an area where the grass is dense motor will make more effort as I can ask him limits to current consumption?
I thought if I put a fuse on and if the motor requires more than a certain current the fuse blows thus safeguarding also the engine.
If the motor is being driven too hard, simply cut out for a few seconds... The fuse normally protects the wiring if there is a short,
its a different issue and should always be there is any high-current equipment.
If you have plenty of spare fuses you can use the fuse as a cutout for the motor, but I think that's not
the best way, you'll lose fuses in the grass and then damage the blades on them if you're having to
replace them constantly!
[ The other thing that you might have neglected is that RC motors are usually designed for
powerful air-cooling (if they drive a propeller), a mower is not going to give you as good motor
cooling I reckon ]
As regards the cooling I assumed to run the engine at about 20% and more add a cooling fan for the engine.
I though I did not understand what actually might be the best solution in order to avoid engine failure .... if my engine that theoretically absorbs up to 30 A mount a feeding current sensor of the engine and when the current exceeds 25A turn off the engine? and then turn it back on shortly after hoping to have less resistance from the grass?
Marco3615:
As regards the cooling I assumed to run the engine at about 20% and more add a cooling fan for the engine.
I though I did not understand what actually might be the best solution in order to avoid engine failure .... if my engine that theoretically absorbs up to 30 A mount a feeding current sensor of the engine and when the current exceeds 25A turn off the engine? and then turn it back on shortly after hoping to have less resistance from the grass?
I think the reason they use petrol is because it can run for ages. If you're going to be cutting thick stuff with electrics, your mower will probably run out of juice (electricity) pretty quick. Maybe the same issue even if you're cutting thin stuff with electrics. But, let's just say there's no energy limitations, then you probably need a system that cuts the engine if the current is exceeded for a chosen amount of time.....eg..... x-seconds. And the fuse is also used for good measure.
which could be a way to turn off the engine if the current exceeds?
Marco3615:
which could be a way to turn off the engine if the current exceeds?
You mentioned something about arduino controlling the system. So need to use the arduino to turn off the engine.
Maybe a hall effect current sensor (0 to 50 Amp capability) could work for you.
Thank you so much
And if I wanted to use a dc motor with higher power (perhaps recovery) and just wanted to check with the relay. What would be the best relay module for use with Arduino?