Instructables

Battery life indicator for Arduino powered fish feeder

Hi all,

So I am basically a noob in electronics and a 1st time arduino user for my project.

I need to do an automatic fish feeder and this is what I have in mind:
I'm gonna use an arduino UNO R3 to connect it to these following components:
- a 16 x 2 LCD Display (connected to RTC chip)
- a small DC motor
- 2 pushbuttons

So these are the main components and I need the arduino to be portable ( So has to be battery powered - Maybe a 9V batt)

As such I have 2 questions:

1) Is it possible for ALL the components to run using power from arduino?

2) I need to add a battery life indicator as well.. how do I go abt doing it?

Hope you guys could help me

Depends on the motor being used. Motors tend to draw a lot of current when they first start up .So even a short turn will draw a lot of power. So you'll want to use a motor shield and a separate power source for the shield. The 500mA offered from the Arduino's power pins won't be enough. Unless you use a small hobby servo.

You can have the Arduino do the battery life test but may not be very reliable. So you may want to build a separate circuit for that. Here is a simple battery indicator circuit.
http://electroschematics.com/993/9volts-battery-indicator/
kurtselva (author)  mpilchfamily1 year ago
Hey thanks for the reply

I was thinking of using this servo:
http://www.robot-r-us.com/motor-rc-servos/sub-micro-generic-servo.html

So do you think it needs a external power source? Actually how do you determine if the component needs an external power source or power from the arduino is sufficient? (Sorry for the noob qn)

And just to clarify, each I/O pins from the arduino can only provide max 40mA right?
The arduino can only offer a max of 5V @ 500mA. If the servo draws more than say 300mA then you will be working the voltage regulator on the Arduino too hard and need a separate power source. The servo you choose should be fin and can be connected directly to the arduino without the use of a shield. The I/O pins are not going to be providing the power to the servo just a signal to the servo to move it. The servo has 3 wires. Your ground and power wire will go to the 5+ and Ground headers on the arduino then the 3rd signal wire will connect with an I/O pin of your choice.
kurtselva (author)  mpilchfamily1 year ago
For the low batt indicator, I'm thinking of using arduino to test the battery life. And if the battery is low, the LCD display will indicate a warning (like "low batt").

So any idea how to do a low batt indicator circuit for arduino? Some sites say use voltage divider while others used some chips..
Like i said using the arduino to test the battery may not work well. The LCD may start fading out before the arduino notices the lower voltage. To test the battery level with the arduino you would have to use the analog inputs which rely on the voltage from the battery as a reference. Anolog reading will vary widely as the voltage from the batteries drops. A very simple battery indicator circuit like the one i linked to is your best option. When that circuit lights the low battery light it can send a signal to the arduino so you get a low bat indicator on your LCD.
kurtselva (author)  mpilchfamily1 year ago
Hey, do you think this schematic would work?

http://www.rmvhf.org/wordpress/?page_id=889
kurtselva (author) 1 year ago
Additional info: The motor will only make 1 turn at a low speed at specified intervals (say at most, 1 turn per 3 hours)