Help... I'm at my wits end

[chimpfunkz]

So I'm currently building a robot that will follow a line. It is powered by a combination of an arduino Mega microprocessor, a Pololu QTR-8RC sensor array, and an Ardumoto motor controller. I am able to run the ardumoto and arduino chip, or the Sensor array and Arduino chip, but I am unable to power both at the same time. I need some help.


Currently, The Arduino chip is being powered by a 9V battery. I have the 5V output from the arduino connected to the Vcc on the Sensor array, and the ground form the sensor array connected to the arduino's ground port. Then, I have a 9V batter connected to the Ardumoto's VIN input. Then, The Ardumoto and Arduino's VIN ports are connected. The problem I am having is that is seems that either the ardumoto can be powered, or the Sensor Array can be powered, but not both at the same time. Help me please.

[Soeren]

Hi,

A 9V (PP3) battery is not very strong, so the available voltage will fall when loaded.
Use 6 AA-cells instead and you'll be able to power it all and then some.
If at all possible, get rechargeable NiMH cells, it will save you a bunch over alkaline (non-rechargeable) cells and don't ever use carbon-zinc.

[chimpfunkz]

Thanks for the advice. Just to be clear, would I be connecting the 6 AA batteries to the Ardumoto or the Arduino?

[Soeren]

Thanks for the advice. Just to be clear, would I be connecting the 6 AA batteries to the Ardumoto or the Arduino?

If the 5V regulator on the Arduino can handle the motors as well, you should drive both the 'moto and the sensor array from that and use the battery (the 6 AA-cells) on the Arduino.
However, depending on your motor(s), it may be too much for the regulator. Measure the current taken by the 'moto when driving the motors and see if the regulator gets hot.

If it won't work with both at the regulated 5V from The Arduino...
The L298 (the chip used in the 'moto) can only take 5V at the logic supply, but can handle up to almost 50V on the motor supply - I cannot see, from the documentation, whether these two supply lines are connected on the 'moto, but if they are, they should be limited to "5V".
Using four (4) AA-cells will be OK though (absolute max. 7V). Four alkalines will be ~6V and 4 NiMH will be ~5V.

Yet an option would be to add a regulator to the 'moto and supply both boards from "9V" i.e. 6 AA's.

[billhowl]

Are you still using this motors?

this motor power from 1.5V to 4.5V(Max) having running current about 660mA, the L298 have internal voltage drop about 3V, 6 AA batteries on alkalines cell will give you 9.
The arduino Mega 5V regulator was not LDO need about 7V input to work and only can supply 800mA.
Hence if you supply both Arduino and Ardumoto with 9V (6 AA batteries on alkalines cell) will have problem over supply your motors.
You will need 4 AA batteries to power the motors and still can use your 9V (PP3) battery to power your arduino Mega.

[chimpfunkz]

I am not using the Tamiya motors anymore. Instead, we are using the Micro Metal 100:1 HP motor (http://www.pololu.com/catalog/product/1101) driven by an ardumoto. I says that the required amperage for the motors is 80 mA free run and 160 mA stall. Does this mean that using the 9V (PP3) battery connected directly to the Ardumoto's Vin, the motors aren't getting enough current/voltage? or is there another problem that I am not seeing? Thanks for all the help. It is really appreciated.

[absentwizard]

You might be kind of pushing it. Ultralife's U9VL (one type of their PP3) is rated for 120mA continuous discharge. Generally speaking, you don't want to push more than 60% of that rating in the first place.

(Their site link is broken. Check Google cache for the datasheet.)

[chimpfunkz]

So what you're saying is that in order to fix the problem, I need to get a better battery to power the Ardumoto? would be be able to reccomend any, preferably one you can buy on amazon but if not a good, reliable battery?

[chimpfunkz]

So I am planning on getting something like this:
 (http://www.all-battery.com/li-ion1865074v2600mahbatterypcbmodulewith22awgbareleads.aspx)
It is a 7.4V battery, rechargeable, that can provide 4.4 Amps of power. Will this be enough power to power my motors, and will the motor shield (the Ardumoto)  be able to handle the voltage and amperage? if not, are there any alternative battery supplies/motor controller combo's that will work for me

[billhowl]

The battery will do, make sure you get the Li-ion charger too.