building a cheap tone/signal radio for a 3 button controller

General project help for Adafruit customers

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
dandenson
 
Posts: 52
Joined: Fri Oct 04, 2013 4:48 pm

building a cheap tone/signal radio for a 3 button controller

Post by dandenson »

I'm building an arduino project (pretty simple, 3 buttons and the keyboard library) but want to add a remote set of buttons as well.

Basically, I'm looking for some help making a very cheap 900Mhz or other free band transmitter to send button presses up to 10 feet indoors. I'm hoping for the remote unit to no have to boot or run any code, just a button press closes a circuit to activate so that it can be battery operated for many months. The receiving side will be a USB powered arduino.

Thanks for any advice!

User avatar
zener
 
Posts: 4567
Joined: Sat Feb 21, 2009 2:38 am

Re: building a cheap tone/signal radio for a 3 button contro

Post by zener »


User avatar
dandenson
 
Posts: 52
Joined: Fri Oct 04, 2013 4:48 pm

Re: building a cheap tone/signal radio for a 3 button contro

Post by dandenson »

That PT2206 looks nice! What's the story on 315Mhz? I that free to use in the US? I need something that doesn't require a license.

Looks like pairing this with the 315Mhz momentary receiver is exactly what I need.

User avatar
zener
 
Posts: 4567
Joined: Sat Feb 21, 2009 2:38 am

Re: building a cheap tone/signal radio for a 3 button contro

Post by zener »

Yeah. A lot of key fobs use this freq. Range isn't too far though. And you can't transmit continuously. I think the license allows only intermittent use.

User avatar
dandenson
 
Posts: 52
Joined: Fri Oct 04, 2013 4:48 pm

Re: building a cheap tone/signal radio for a 3 button contro

Post by dandenson »

I have an application that uses a keyboard and the up and down arrow keys, so I'm only needing 3 different button presses and only for very short duration. Also, average distance is only 5' though a 10' range would be preferable.

Question is, how does this PT2206 identify the button presses uniquely, in other words how do I make sure that a car keyfob doesnt trigger one of the button presses?

User avatar
zener
 
Posts: 4567
Joined: Sat Feb 21, 2009 2:38 am

Re: building a cheap tone/signal radio for a 3 button contro

Post by zener »

Well, there are a number of reasons that you would not get false triggers. First of all the range of fobs in general is very short, maybe 20 feet or so. So you need to look at what fobs will be getting that close. Then there is the fact that different transmitters/mfgs use different encoding schemes, and ideally ignore all but pulse trains perfectly matched to their own format. How well this chip does that I have no idea. It isn't to hard to do though. Next this chip has 8 (or more) address pins so you can set it so that your neighbors identical fob doesn't (probably) have the same address. So it comes down to some mathematical calculation of false trigger probability. I have no idea what the answer is. Is it 1 false trigger in a year, in 10 years, 100 years, a month? Don't know. Keep in mind it is $7 so if you need perfect performance then you will have to aim a little higher probably. Maybe someone else has an opinion.

User avatar
adafruit_support_mike
 
Posts: 67454
Joined: Thu Feb 11, 2010 2:51 pm

Re: building a cheap tone/signal radio for a 3 button contro

Post by adafruit_support_mike »

The chip also has 12 tristate address pins. That gives you a bit more than 500,000 unique addresses, which severely limits the chance of a collision.

User avatar
dandenson
 
Posts: 52
Joined: Fri Oct 04, 2013 4:48 pm

Re: building a cheap tone/signal radio for a 3 button contro

Post by dandenson »

I ordered parts, so well see how it all comes together.

Locked
Please be positive and constructive with your questions and comments.

Return to “General Project help”