motor type for driving bot that uses grid system to navigate?

At first i tried DC gear motors with H-bridge and PWM signal for speed control but that was a disaster. because they were not able to produce enough torque and speed controlling was very tough. The lowest possible speed with L298N was not enough for me. driving the bot straight was also tough.

So, i tried stepper motors. But they take too much current (one 2BBYJ-48 unipolar stepper eating up two fully charged 250mah 9V batteries in around 1hour) and i don't need that much accuracy and holding torque they provide. i just need to drive my bot of max weight 2 kg from coordinate to coordinate where each coordinate is a 3cmx3cm square on the floor(the bot is 21cmx21cm and i want the bot's center point to reach the coordinate square).

now what kind of motors should i use? the bot will have a raspberry pi and a stepper/servo driven robotic hand on it + a board with 4 sonars at the top of the bot that will keep rotating continuously with a stepper. so i need a lot of horsepower on it. any suggestions for batteries will be appreciated too.

The phrase “DC gear motor” conveys no useful information. You can get DC gear motors that produce a watt or less of power and others that produce 10s of kilowatts. You need to provide a link to the datasheet for the specific motor you are using.

If you mean the PP3 style of 9v battery then they are not at all suited for motors of any kind - they cannot produce enough current. Try a pack of 6 x AA alkaline cells or 8 x AA NiMh cells.

An L298 is a very inefficient motor driver and you may be losing 2 volts through it. A more modern driver that uses mosfets may help.


i used this one -
bought from here -
what controller to use if not L298N?
the thing is these DC motors very low torque and high RPM that i dont need. i need my bot to be slow and accurate. so what do i do now?

I have some gear-motors like that and IMHO they should have plenty of torque for moving a robot.

Have you checked the capability of the motor by connecting it to a 4.5v battery - a pack of 3 x AA alkaline cells? Just now I powered mine with 3v (2 x AA cells) and i could not prevent it turning with my fingers.

The most likely cause of your problems is using an unsuitable power supply. Read the second paragraph of Reply #1.

The L298 has a minimum voltage requirement of about 7v I believe. If you want to work with a lower voltage the Pololu DRV8833 would be suitable, but its max voltage is only about 10v IIRC. The Pololu website has a range of motor drivers. Other suppliers probably have similar products.


even if it manages to carry 2kg of weight and friction from 2 ball casters at front and back of the bot will it be able to accurately navigate the grid system? besides, the last time i used them they had too much speed. any PWM below 100 was of no use. the motor won't spin below 100PWM. I care about the accuracy a lot. because i have nothing that much to know the current position of the bot accurately(i had two encoders that detected motor revolution). if it goes even 5-6cm away from its path it'll be of no use to me. the most difficult problem with these motors was driving both at same speed and making the bot go straight.

if you think it'll be possible to drive them straight with accuracy i'll give them a try again. i've the motors and the wheels. just need a better controller. will this be okay?
will Li ion batteries be okay for it? something like this
i couldn't find any rechargeable AA battery in any local online shop. I'll still try to go to my nearby electronic shops and search for some. Actually i have already bought 5 9V Ni-MH batteries and i fear buying 6 rechargeable AA batteries will exceed my budget. are you sure these Ni-MH wont work?
actually most international online shops dont deliver their product to our country so i have no other way but to buy from local retailers. techshopbd is one of them.

i thought i should add this,

previously i used one 9V Ni_MH 250mah battery to power the L298N and the L298N was powering both motors. the motors were okay with no load. but as i added more weight they became more inaccurate and kept suddenly stopping in runtime.

-- sorry for my bad english :cry:

That motor driver should be much better than an L298.

You won't know if the little 9v batteries are suitable unless you have a bigger battery for comparison. Can you not try a pack of AA alkaline cells - much cheaper than NiMh cells for initial testing.

Ultimately you will only get answers by experiment.