Let's Make Robots!

Make robots talk.. to each other.. dirt cheap!

UPDATE: More info on the subject here: http://letsmakerobots.com/node/5194

Original post:


I have this thing in the back of my mind that "the next step" for me must be my robots talking to each other.

In the very little time I have for building & playing & researching these days, I have been playing arouund with pulsating lights, robots feeling the bass from a stereo, the very useful "external timer" commands within the Picaxe libraries and such.. But have not found that killer app that I was looking for.

Staring out in blank nothing, thinking.. oh, if only I could buy like 10+ Easy Radio transmitters.. but that would be quite expensive.. and so I just browsed, and wow!

You can really get some dirt-cheap wireless communication devices now! Holy cow, tomorrow I will browse more and order some.

How about 10 of these:


- That's 5 robots communicating 2-way wireles for about USD 50 including p&p!! 

- or check out this page for inspiration:



Sworm robots may be just around the corner :)


Let's hear it if anyone can find better deals for robots informing each other, just within a space of say 10 meters. 

I only browsed google for about 5 minutes, sure there is more to find out there :)

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Hey frits,

I was looking at your $5 Rx/Tx units and it seems that they are not addressable. Not that this is a huge deal, but at a minium you will always have to send 2 numbers --the first sets the "address" while the second is the data-packet.


You are a very competent person.
I was wondering if there was a way to utilise the i2c bus since it is already set up for multiple masters. The problem is that both SDA and SCI lines are bi-directional plus even at it's slowest transfer rate it is too fast for audio or IR on a 38KHz carrier wave. You really want something like FM. FM transmitters are very cheap and simple to make but not receivers so much.


I'll make my own protocol :)

I don't know about range but using tone encoder/decoders would be cool as your swarm of robots would talk in audable beeps and sound a lot like R2D2 from Starwars.

They work fairly well, the best way I found to use them is to have a second axe that handles the incoming data. I've got the reciever connected to an 08 which constanly monitors the 433 band. When it receives data, it will put one output high connected to the master (28x) axe's interrupt, then a second output is serial. When the master axe see the interrupt it will read the serial from the 08. 

This was to get around the problem of the main axe wasting time waiting for serial data that may or may not be there (in the magic 433 air). But if you don't need them to receive the data immediatly, you could use the timeout function in the serin command on some of the higher axes to check for serial data every so often (will slow down the program).

 So my point is; I think they are the cheapest way to cummunicate (excluding IR) but you will need to allow for the 08.

You could also use IR sensors that cost less than a buck for 2. Of course you can only send numbers from 0 to 255, but if each bot knows what the number means then it works. You also have to worry somewhat about line of sight but IR bounces a lot. I got an IR sensor to work when the sending and receiver had a kitchen table in the way


Problem is both line of seight, and the processing they take: With an external reciever - like the ones I link to above - you can background-task the listening. The Picaxe has interrupts, check the setint command. 

And then all the sunlight-flourecent-light-problems, I'm not too happy about them :)

The cheap way toys and such communicate is usually with IR. The Wowee robosapiens, quads, what have you react a little to each other, through their flashy IRs blinking at each other. Cheap and works, but think they are typically around a foot (30 cm) from each other when "yakking".

A clue from one swarm robot project I sorta remember seeing, is to  have each bot be a node. One robot gets a message, reacts to it, and passes it on, repeating the message. So you have say 3 robots, 1 in a hall, one at a corner, and another around the corner, the hall-bot generates a message, which the corner bot picks up, and begins moving to, and it reflashes the message to the hidden-botwhihc gets it and travels futher without having line of sight to the hall-bot. Termination could be after the message is reacted to, to sent back an acknoledgment, so the hall-commander-bot can think of something else the underling bots can react to.

But cheap RF is hard to beat for getting more faster better information out and back.

what about sonar?