4 Motor Arduino Project doubts

Using Arduino Project Guidance
1

Hello everyone,

I have to create a car-like robot that will use 4 motors, an arduino UNO, a motor driver (L293D), power supply, etc. So, this is my first time creating a project like this and i have several doubts, so im looking for some help:

I searched online for projects like this and they seem simple, but i dont want to damage any component because im on a limited budget.

My plan of connecting everything is as follows (remember this is a car-like robot):

1- Motor shield L293D goes on top of the Arduino UNO. I choose this driver because it can handle 4 motors.
2- The motors I choose are G12-N20 Geared Mini DC Motor. I choose this one because it offers the torque i need for this. The datasheet of this item shows this important information:

Rated Voltage : 6~12V
Revolving Speed : 100RPM @ 6V
Load Speed: 80RPM
Rated Torque: 2 kg.cm
Stall Torque: 16 kg.cm
Rated Current: 0.07A
Stall Current: 1A

3- Power supply, i choose a 2x Li-ion 3.7V battery 7800 mAh.
4- Connect everything. Motors to motor driver, power supply to motor driver, connect jumper on motor driver so it powers up the arduino uno.
5- Mount everything of top of the chassis. Connect wheels to motors as well.

So, i have several questions regarding this project:

1- As far as i know, the L293D should be used with motors that have less than 600 mA of current consumption. The datasheet of the N20 Micromotor says that it has a stall current of 1A, wont this be a problem?

2- Connecting the power supply to the motor shield and connecting the jumper so it can power the arduino, it this the recommended way of doing it? or should i use a separate power supply for the arduino?

Thank you in advance!

3

Are You sure that the L293D outputs 5 volt? The L298 does but the 293?

Check the absolute maximum ratings for the circuit, in the datasheet. Good You know the question!

4

I do not see any method to monitor the wheel RPM so you can make the robot go straight or turn.

5

The L293 DC motor driver is ancient and inefficient technology. Its BJT darlington output stage will drop 2V to over 4V of the supply voltage, dissipating that power as heat. That means that that driver is less than ideal for battery powered projects. Modern MOSFET output drivers are much more efficirnt.

Pololu has a good line of DC brushed motor drivers. They provide good tech suppory an each product has an page to instruct on its use.

Choose a motor driver based on the motor supply voltage and stall current.

6

Im pretty sure the L293D can output the necessary voltage to the Arduino board. Have seen several projects using this combination.

Maximum absolute for the L293D are 1.2 A for less that 100 us. I believe that 4 motors that each have a 1A stall current its extremely dangerous.

7

Yes, you're completely right. My partners and I thought that we can kind of use ultrasonic sensors to measure distance to a front wall (because the robot will go straight to a stair step and climb it) so if we measure distance with both sensors we could correct the path.

We didnt investige this much because its not a top priority aspect right now, but if you know a better approach im all ears.

8

Got it. Most of the motor drivers are single/dual, this means that i need two dual motor shields to manage 4 motors? (4 channels).

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Can You point into the datasheet showing that? It looks like the low voltage parts can use either motor power voltage or externa voltage. Conclusion: No 5 volt generated.
Do You think of a board containing the L293D, having more circuitry "doing things"?

What's the current situation? What works and what doesn't?

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I think that i was confused about how the L293D and the Arduino are powered when they are togheter. I dont believe now that the L293D can output 5V to the arduino. If im using both i should use a separate power supply for each part.

The construction of the project has not started yet. We are in the Planning/Design part of the process, right before ordering the parts. Because we are completely new to this kind of projects we are using a lot of our time to investigate this topics first.

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Using proper power for the controller, the controller can power the 5 volt circuitry via its 5 volt pin, or the strap on the driver fixes that.

Rather, the design is ongoing. Fully okey.

As stated by @ groundFungus that driver is a low cost, power wasting thing, scrapping 2 - 4 volt. This is unfavourable regarding battery operations.
To give motor the full voltage the power supply needs to be give some 2 - 4 volt higher then the motor voltage.

12

Yes, that's the way you can do it.
The 2S LiPo battery is then connected to V-in of the Uno.

I wouldn't worry too much about the warnings for the L293D.
It's indeed an old lossy dinosaur, but it will likely work for a toy setup.
Leo..

13

That is quite an assumption. Do you or your partners drive a car? Does it go straight without any help?

1 Like
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We did not make any assumptions.

15

Then you would not be posting on the Arduino forum.
Lets assume you can measure the front wall. What is happening then? Does your robot move?

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