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Topic: Robot Wheels are not Turning Enough (Read 1 time) previous topic - next topic

Empty

Hey,

I have bought myself a what once was a RC controlled car, to make it into arduino controlled one. Everything is going fine except for one problem im encountering, which is that the front motor, that controls the front wheels, doesnt turn them that much. While im tryin to turn, it take a huge radius to do that, either it is turning left or right.
The front wheels are connected, and this connection has a spring, that makes the wheels straight, if the motor is not spinning.


I'd like to know if someone has an idea that would help me, or send me to another direction.

Here's what Im using:
1. L298P motor shield
2. 9V alkanine battery for the shield
3. 6xAA 1.5V batteries for the Arduino Uno
Unfortunately I dont know whats the voltage of the motor yet


Cactusface

Hi Empty,
               The L298 is a very poor motor driver as you lose power in the output transistors, about 2-3 volts. Please don't tell me your using one of those tiny 9v batteries for the motor shield!! it's useless and can't provide the current the motors need. The motor shield needs the 6xAA's the Uno could run on the 9v as long as there are no real current demands on the I/O pins... Remember to connect it to the Vin pin, not the 5V pin.

I've built a few buggy-bots you can see them here: www.melsaunders.co.uk
Hope it helps...

Regards

Mel.

Open your mind! But not too far, your brains might fall out.
Also like Photography, model building and my 300+ Cacti and Succs.

Empty

Thank You for the help, Mel.
I have a L9110s motor driver lying down somewhere, but I suppose its not so much better?
And yeah, I was using a simple 9v battery, as the tutorials Ive seen suggested and I thought it would be a start just to see how things work.

Cactusface

Hi,
    The L9110 is a much more upto date device and works well, these modules are available very cheap on ebay, etc. THe L9110s chip works a bit different to some others, in that the 2 control input pins are DIR and PWM, so with only 2 pins you can control direction and speed the L283/298 needs 3 or 4 control lines, depending how you do it.

Have you tried changing the battery packs over as I suggested?? it really will make a difference to your motor speed. What tutorials have you seen, NOT Instructables! their full of rubbish and errors....

Does the motor look like it's well made and capable of a good speed, it's likely to be about 6V, what was the power pack in the car? when you got it?

Regards

Mel.
Open your mind! But not too far, your brains might fall out.
Also like Photography, model building and my 300+ Cacti and Succs.

Empty

The car came with no batteries, but  it requires 5xAA 1.5V, which is written where those should go.
Unfortunately, I im not able to switch the battery packs at the moment, since it requires some soldering, which, at the time, I cant do. But I'll keep trying to connect it somehow, to see how things work out

Empty

Alright, it seems that using the L9110s motor driver, and switching up the batteries worked.
Now the question I have, will I not overheat this motor driver, by using two motors and supplying it with 9v, or maybe even 7.5v, using the 5xAA slots that the car has?

MarkT

Quote
2. 9V alkanine battery for the shield
3. 6xAA 1.5V batteries for the Arduino Uno
Wrong way round, surely?  Motors need current, lots of it.  9V battery is utterly wimpy.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Cactusface

Hi,
     That's just what I said! Use the 6x AA's for the motor shield, and no it shouldn't over heat!! I take it the shield will take 2 motors most do? If it's not got an heatsink the CHIP/s might need one, or forced air coolling..

Battery basics big size lots of current, small size dribble current, but if the battery consist of lots of small cells, then it might not be TRUE!

The Uno needs less then 100ma to run, motors depending on quality/type start at 50-100, but usually need a lot more for power and speed..

Regards

Mel.
Open your mind! But not too far, your brains might fall out.
Also like Photography, model building and my 300+ Cacti and Succs.

Empty

#8
Nov 19, 2016, 08:29 pm Last Edit: Nov 19, 2016, 09:36 pm by Empty
Alright, so I switched up the batteries, and here are the results

1. The L298P is still not doing the job.
2. The L9110s is doing better, but it heats up so quick, so thats a no no.

I still cant measure the current draw of the motors, but my guess is that they draw more than 800mA, so the L9110s overheats.
Now the question is, why the L298P doesnt do its job. It can give 2A per channel, which I think is surely enough, but again, need to check, or as Mel said, it has something to do with the power loss?
Or maybe the batteries are close to being done, because, they are not rechargeable (the next ones Ill buy will be).

Any ideas? As you can tell, Im not so good at the electronics stuff, im enjoying the program part more, but its hard to test the code, when the wheels wont turn.

Also, thank You for your help so far.

EDIT: im looking at other motor drivers, that I could switch to
https://cdn3.bigcommerce.com/s-vt19phz/product_images/uploaded_images/l298n-motor-driver-from-tronixlabs-australia.png
this is L298N, does it have the same flaw as the L298P one?

Cactusface

Hi Empty,
                The L298/283 both use power transistors on the output, this results in a power loss across each one. My early bots used the L283 and with 4-6x AA's ran well but they were high capacity rechareables. I now use Lith-ion! these are lighter in weight and more power for their size, 2xAA's(14550) give me 7.2v at 1800ma, in half the size and weight, a double wammy!!

The L298 may work better if you give it higher volts and the current, if your using primery battery then they need to be top quality, if they excist??

2A should be enough but I know nothing about your motor, some RC car motors can suck a lot of juice at speed, how fast do you want it to go?

Some of the new driver modules are tiny, like the pololu ones based on the TI (Texas Instruments) DRV8833/35, sure this was the last one I used.. take a look on the net, you can get cheap Chinese versions that I find work fine.

Where in the world are you?

Regards

Mel.
Open your mind! But not too far, your brains might fall out.
Also like Photography, model building and my 300+ Cacti and Succs.

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