Powering 4 x Sharp GP2D120 IR Sensor and Tamiya 70097 Motor

Hi all!
This is my first post so please tell me if there are any things I’m doing wrong/ could improve on! I’m relatively new to mechatronics and am working on a university project to build a “one-button-start” vehicle to navigate a track and climb a step.

The mechatronics aspect of our design consists of 4 x Sharp GP2D120 IR Sensor, a Tamiya 70097 Twin Gearbox Motor and we are using an Arduino Eleven (essentially Arduino uno) board. I was just wondering what would be the best way to power all these? I was thinking I could run the sensors via an external power source (4x1.5V batteries with a voltage regulator to bring it down to 5) and then run the motor via the board (2x1.5V batteries). This seems logical to me however as I said I’m very new and this may be completely wrong.

The specs for the motor and sensors are:

Tamiya Motor:
Typical Operating Voltage: 3V
Free-run current (no-load current when disconnected from gears, so total no-load current will be slightly higher) @ 3V: 150mA
Stall current @ 3V: 2100mA

Sharp GP2D120 Sensors:
Supply voltage: 4.5 to 5.5V (I’ve read that 4.5V isn’t enough so probably more like 5-5.5V)
Consumption current: Typ. 30mA

There some more specs for each but I didn’t want to clutter the post so I think these are most relevant.

Anyway thanks in advance for all the help! Let me know if you need any more information :slight_smile:

and then run the motor via the board (2x1.5V batteries).

What does this mean? The Arduino will not supply the proper voltage or anywhere near enough current - those motors need 4+ amps at stall speed. Which board are you referring to?

Thanks for the reply! The board I was referring to was my arduino Eleven board and I was thinking of using some sort of voltage regulator (although I've now changed my mind). Since posting this I'm thinking that I will instead run the 4 sensors through the board (at 5v) and power the board with 6xAA batteries. Then power the motor with 2 or 3 pairs of AA batteries in parallel to maintain 3V and satisfy the current needs. However, you mentioned they require 4+amps to run? So what do you think of my setup and how many AA batteries (or otherwise) would you recommend for powering the motor?

Then power the motor with 2 or 3 pairs of AA batteries in parallel to maintain 3V and satisfy the current needs.

Two or three pairs of AA batteries will not provide 4A. You really need to look at RC car batteries.

Sorry I'm a bit confused can you just clarify why its 4A? Because it says that the stall current 2.1A and I thought that was the maximum current it will require.

Because it says that the stall current 2.1A and I thought that was the maximum current it will require.

Aren't there two motors? If not, then I'm wrong.

Oh yeah you're absolutely right, so that is the power for each motor? Also I should have been more specific at the start, the vehicle has to only navigate a track and climb a step which will take less than 2 minutes at a time, then we can replace batteries if necessary, would this affect the required batteries (sorry I should have mentioned this earlier)

You may be able to get away with using two Alkaline "D" cells for the motor power. Otherwise, a single Lithium Ion rechargeable such as a 16850 (or two of them) would probably do, or a model battery specified for the job. Note the recommendation to charge them (with the correct charger) outdoors on concrete and preferably in a (metal) sand bucket with a cover. XD

Presuming you also use a motor controller like the Pololu Low-Voltage Dual Serial Motor Controller which is designed for this purpose.

This power source has nothing to do with the Arduino/ "Eleven" of course, and unless you are using switchmode regulators such as provided in some ESC (Electronic Speed Controller) units for models, it is not a good idea to attempt to use the same battery for both purposes as voltage "sag" if the motors are stalled may cause the MCU to behave randomly.

You can probably get away with using three AA alkalines - 4.5V to power the "Eleven" through its "Vcc" terminal.

Unfortunately I don't have the Pololu Low-Voltage Dual Serial Motor Controller :frowning: We were planning on using an l293d H-bridge micrcontroller to control the direction/speed of the motors, is that sufficient do you think? When you say

it is not a good idea to attempt to use the same battery for both purposes as voltage "sag" if the motors are stalled may cause the MCU to behave randomly

do you mean that I shouldn't power the four senors through the arduino board? Because I'm not sure if you misunderstood me or I am misunderstanding you but my plan is to power the motor seperately and then power the sensors via the board.
Thanks for your help! :slight_smile:

Teamteabags:
We were planning on using an l293d H-bridge micrcontroller to control the direction/speed of the motors, is that sufficient do you think?

It does not sound like it. It is specified for 4.5V minimum whereas you are looking at 3V, and 600 mA for the "d" version. I cannot see on the datasheet (perhaps I am not looking hard enough) just what voltage drop it will give, but an "H-bridge" loses twice, once on the positive and once on the negative, so you might need to consider that Popolu purpose-designed system or using at least 4.5V and wasting some - and a heftier H-bridge anyway!

Teamteabags:
do you mean that I shouldn't power the four sensors through the Arduino board?

120 mA will not be a problem as running from 4.5V as alkaline batteries, you will be powering the sensors directly from the battery as you are bypassing the regulator anyway. It would not be too unreasonable even if you were powering it from the regulator, as long as you do not add too many other things.

I was referring to the recommendation to use separate batteries for the electronics and the motors. The H-bridge of course is necessarily powered from the motor supply.