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Topic: Newby, wondering if this is what I need (Read 1 time) previous topic - next topic


I would like to make a droid phone interect with 8 relays.
I think this is the product I need.

What is the best version?
Is there some sample code to get started on the droid?

I am a php devloper, and I restore cars as a hobby.
However, I know nothing about makeing a phone interact with a mechanical device.

I'm here to learn.


Read this: http://developer.android.com/guide/topics/usb/adk.html


Sep 15, 2011, 08:02 pm Last Edit: Sep 15, 2011, 08:10 pm by jwatte Reason: 1
Maybe this should go in the "project advise" sub-forum?

I'm also an Arduino newb, but I've done other integrations in the past. I see four separate challenges you need to overcome:

1) Wiring relays to the Arduino. There are "digital out" pins on the board that you can use, but unless the relays are really triac/opto-couplers, you will need some driver electronics/buffers to avoid overloading the chip and frying it.

2) Writing code for the Arduino to read commands from the phone (or computer) and turn it into relay signals. This sub-forum is right for that challenge. Your loop would basically just read data from the serial port, and turn digital pins on and off based on the commands that come in. You could make it simple: uppercase letter (A, B etc) to turn on; lowercase letter (a, b, etc) to turn off, for example.

3) Wiring the Arduino to the phone. If the phone can act as a USB master, then this probably means getting the right cable from the phone to the Arduino USB slot. If the phone cannot act as a USB master, you will need some other way of communicating. There is a Bluetooth shield, for example, perhaps that will work.

4) Writing software for the phone to talk to the Arduino. This is probably going to be a lot harder than the Arduino-specific bits, unless there is some control software for the phone already that is compatible with whatever connection you use from the phone to the Arduino board.

There's some question about how much you want to build yourself, and how much you want to buy ready-made, too.

I just saw Frank's response -- it looks like the Accessory Mode solves problem #3, assuming your phone supports it.
If you then buy a ready-made board like the SparkFun IOIO, they already solved #2, so all you got to do is #1 and #4.


Sep 15, 2011, 09:19 pm Last Edit: Sep 15, 2011, 09:47 pm by frenchsquared Reason: 1
I want to figure out a way to build an application on a droid phone that will trigger up to 8 12v relays.
Preferable using bluetooth.

I think I need this board:

What do I use to power the Arduino board?

I was reading the blink loop. That is basically all I need this to do. I just need it to blink a relay.

What do you guys recommend.
What Arduino boards and software?

I am a complete newb. I am a php developer by trade so I understand code.
I also restore cars so I am fine on the car side of this project.

I need to figure out how to connect the relays to the Arduino board and
how to make the droid phone talk to the arduino board.



Powering a standard Arduino from a car battery (e.g. 12 volts) ? If so you can just connect it directly; the regulator can handle 12v easily.

Connecting relays is pretty easy, you just connect a pin from the Arduino to a resistor, then to a transistor, and connect the transistor to the relay. Here's the standard implemenation:


As far as which board, if you go with the Arduino + Bluetooth from your link then you're set, but you'll need a separate circuit to convert 12v to 5v. Here's one idea:


I can't help you with the Bluetooth link between the phone and the board but there are other people who've done something similar; "arduino bluetooth android" turns up several interesting hits.

Good luck,


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