Good day everyone.
I have recently started on a project where I have to control a miniature wheelchair with a motor. The only question that remains to be answered, is if I should use a motor, or one with a gear reduction gearbox.
Example:
Geared Down Motor: Amazon
Ungeared Motor: Amazon
I am looking to use a normal L298N Motor Driver to control two opposite motors.
Any advice would be greatly appreciated.
Thank you.
-Dawn
If that's the only question, then:
You should use the one with the gearbox.
A ungeared motor shaft speed is usually over 1000 RPM. Way too fast to be controllabe in your project. Decide on a top speed for your wheelchair then search for a motor that, with gear reduction, yields the range of speeds that you want.
And while you are at it, look for a better motor driver.
Pololu has a good selection of geared motors and motor drivers.
Care to show the mechanical part of the chair and the bearings supporting the wheels. And how you will power the wheels with the motor/gears. Will you allow the chair to be moved without power? Will you allow the chair to turn 360 degrees?
Thank you everyone for your responses, they are greatly appreciated.
I will definitely opt for the geared motor in that case.
In regards to the bearings or mechanical aspects of the build, truth be told there isn't much to show for yet, as the design will form around the selection of motors and whatnot.
I anticipate that the wheelchair will have 2 powered wheels in the rear, and 2 pivoting wheels at the front. The 2 rear wheels will be used turn, move forwards and backwards.
Depending on the type of motor, I think a 9V Battery Pack (probably a Li-Po, quite high power draw) would work fantastically.
Thank you again.
-Dawn
Those are hobby motors. They will not push (or stop) much mass.
But again -
(Yes - I also thought this would be a large wheelchair at first)
Hopefully, it’s a toy wheelchair with no people on it - wouldn’t want to see a crash.
Sorry. I missed that.
The design had better form around the structure of the chair, and include support for that wheel assembly. Then add to the design for power and control. The design also needs to control braking for the wheels for safety to avoid a run-away chair.
This statement has me confused. The 9V battery type has rather limited current rating and Amp-Hours. With a Li-Po 9V, the motor draw will likely trigger the battery over-current protection circuit and have the battery shutdown its output for some time.
Thank you once again everyone for the responses - all of these are valid ideas to consider.
I think I will opt with the geared down 3-6V motor, and I will try to power these with a 7-8V Battery. The miniature model will be relatively small, and so 2 of these motors (one on each axle) will suffice.
I have to still consider the physical design of the product, but that will have to take the shape as the circuit itself finalizes.
-Dawn
This could damage the motors. The battery voltage should reflect what the motor needs, otherwise you will need to somehow drop some of the voltage, which will be inefficient and waste battery capacity.
The inefficient and outdated L298 will probably drop around 2V. If you use 8V battery, the motor will only receive around 6V and 25% of the battery capacity will be wasted as heat by the L298.
If you use a more modern motor driver, as suggested already, it will drop almost no voltage and waste almost none of the battery capacity. So you can use a 6V battery for your 6V motor. TB6612 might suit your needs.
I am currently thinking of adding 4-5 AA batteries (6V - 7.5V total). I realized the motor driver I have isn't ideal, but I am on a tremendous time crunch for the project and I've already ordered the parts.
With the 2v drop on the current driver, I would expect the voltage into the motor being 4-5.5V. That works overall, considering that the motor is operable between 3-6V, and using PWM, I'll hopefully be able to have more accurate variance in this regard.
Looking forward to hearing your thoughts.
-Dawn
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