Let's Make Robots!

Radio emitter and receiver query

Hi all..

I'm new here so hello and be gentle!

I am looking into developing a small bot that could follow me around at a set distance (approx 3m) behind me. Ideally I would like to find a cheap pair of radio emitters and receivers that I could use to measure distance (2 small emitters placed on me and the receivers on the bot) This way I could separate the receivers on the bot to triangulate the position of me relative to the bot, this being used to guide the bot in my direction.
Are such things available as I can’t seem to find anything anywhere.

Has anybody done anything similar to this who could share some of their ideas or findings. I have an alternative idea as follows but it’s not as solid. Comments on potential issues would be greatly appreciated.

Use an ultrasonic range finder mounted on a servo or stepper that scans left to right until it finds a target (me) and returns the distance and angle so as to guide the robot. It is then continually scanning left and right at the target until it passes the target and then reverses direction and so on – this would give an angle range of the target with the direction being between the 2 extremes.

Thanks again for any help.

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No Way !.  This is exactly the application i was eventually going to use the system for. Damn aussies got their first ! (no offence intended Ant) - But at least i (well we) was on the right track regards the principle..

Going to give it a go with the ultrasonic transmitter and sweeping receiver (hopefully i wont need the "equivalent of 3 pcs to process the information!)..

Thanks all again!  No doubt i will back for more guidence (never picked up a soldering iron in my life!)

Hi lostmyed and other robot people,

I am beginning a similar person-following project for school using a non-image processing solution such as GPS or RF transmitter/receiver. GPS seems not accurate enough, so I'm also leaning toward the RF transmitter/receiver for guidance. I also saw that Shadow Caddy and was very impressed. Do you have any tips on processing the location? Is there any software that ties into the receiver to provide useful location tracking data?



Good implementation of a following robot, and done by an Aussie to boot! Some other interesting inventions on that site too. I especially like the this one just for its name.
But maybe you could use a simpler solution : you carry several IR leds as a beacon and your bot has two IR receivers to seek it, and you use the ultrasonic rangefinder just to be sure your bot stay at a safe distance...
Thanks, but would that work reliably in both light and dark conditions i.e. in sunlight ?

You're right, i have to stop thinking only indoor...

Maybe with a strong beacon? But i don't think so...


(jeez, i just keep being wrong on this thread!)

I would think so, with a pack of 5 ir emmiters I think it would be possible to get some good range. heck with a pack of 3 emmiters you should be able to get some decent range....even in sunlight.


You could have the following setup.

1) The robot sends an ultrasonic pulse at a certain frequency (it's basically yelling 'MUMMY WHERE ARE YOU?'. This pulse will take a certain time to travel to the receiver of mummy

2) Mummy receives this message and ....

3) responds by sending an 'I am here you little twit' back (same distance, same time lapse).

4) twit receives the signal and calculates the distance to mummy. If distance to big, than move, if too small then just stop/slow down.

If 2 doesn't happen then mummy is out of range and the robot has to stay put. (mummy is in the shop just wait until she's back).

I am not sure about the directional stuff though ....


P.S. Sigh.... replied to the wrong message in the string.... sorry




1) Mummy, where are you?!
2) Mummy responds "MMWAAAAAARRRHHHH"

 As opposed to the Zombie version which tracks brains ;)

*truly sorry about that. those responsible (me) will be sacked*

No thanks for your efforts ! I can’t believe how quickly people have contributed and replied, I’ve got so much food for thought now. Much appreciated.