Is this motor powerful enough to run the chasis? -Automatic Weeding Robot #4

RE: Is this motor powerful enough to run the chasis? -Automatic Weeding Robot #4

shabaz — Mon, 21 Jan 2019 14:10:55 GMT

Hi!

As DAB and others mentioned, it looks like a torque issue. From the last video, it looks like it can travel quite fast, so it's likely that those motors are not geared down enough, causing it to stall if conditions on the ground are not perfect.

The motor looks very low-power and poor quality, they look exactly like motors used for the past 20 years in children's underpowered toys, so there is a limit to how much gearing down you can do before its too slow to be of use.

You mention you have Maxon motors too - they are famous for powerful motors, so if you already have those then it's worth a try if you can find a way to gear them down.

Regarding a driver, it is difficult to build a discrete one, (plenty of bad circuits online):

[View:/resized-image/__size/407x244/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-251609c1-850b-43a8-835a-b9ab5bd20368/contentimage_5F00_189946.png:407:244]

but there are off-the-shelf options, like these:

ROADTEST REVIEW: TLE94112LE infineon motor driver shield.

(See datasheet page 73 to see how to parallel outputs for more power capability).

or DC Motor Control Shield for Arduino

(only supports one motor so two boards needed, lots of power but only for motors that can work with 8V or higher, so might not be suitable for the motors you choose to use).

RE: Is this motor powerful enough to run the chasis? -Automatic Weeding Robot #4

weiwei2 — Mon, 21 Jan 2019 13:35:17 GMT

On side note, since i am not able to do any physical modification on the bot for next few days, i am doing some 'online research', i do have a few pieces of high current (as in >60A MOSFET), anybody has tried to build DC motor driver out from MOSFET before? any good reference?

as i have pointed up above i also have 'research' onto 2 MOSFET half bridge driver, but any successful will be of great help [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-251609c1-850b-43a8-835a-b9ab5bd20368/contentimage_5F00_1.png:16:16]

another that i kinda don't understand is, if i use MOSFET to drive the DC motor, do i need the flyback diode across the DC motor? i do have some 30A rectifier diode, 2 pieces of current sensor (which i think can do over current protection)

RE: Is this motor powerful enough to run the chasis? -Automatic Weeding Robot #4

dubbie — Mon, 21 Jan 2019 10:14:43 GMT

It does seem to be a problem of getting more torque to the tracks. As DAB has previously indicated, you can get more torque from your existing motors, or as you are thinking, you could get more torque from bigger motors - although bigger motors will probably go faster which might not be what you want. Maybe bigger motors with motor gearing might work.

Dubbie

RE: Is this motor powerful enough to run the chasis? -Automatic Weeding Robot #4

jw0752 — Mon, 21 Jan 2019 04:45:44 GMT

Hi Cheah,

I see from the data sheet that the motor is available with different gear boxes attached. I suspect that you have the 3 stage. You might see if it is available with the 4 or 5 stage. This would slow it down but make it more like a tank. It would also allow it to run on a much reduced current and allow you to continue with the L298.

John

RE: Is this motor powerful enough to run the chasis? -Automatic Weeding Robot #4

DAB — Sun, 20 Jan 2019 20:05:35 GMT

The real issue is that you need more torque rather than speed.

By using the motors to directly drive the belt you put all of the force directly on the motor.

To get more torque, you want to used various gearing to turn the speed of the motor into more force to drive the belt.

By allowing the motor to run at higher speeds at low torque, you greatly reduce the current needed to move the chassis.

So look into using gears and or belts to enable your motors to create more torque.

DAB

RE: Is this motor powerful enough to run the chasis? -Automatic Weeding Robot #4

dougw — Sun, 20 Jan 2019 15:22:32 GMT

An LMD18200 driver would supply 50% more current but it might not be pin compatible.

Could you gear it down using a smaller sprocket?