I'm working on building a bot that returns to a specific base station sans GPS. How can this be achieved keeping the costs low? the bot has to be able to come to a certain proximity of the base station.
The complete project
a robot that receives a message from the base station to go around and sense certain parameters. It goes around senses and returns to the base station. Then transmits the data over to the base station. The base station is connected to the internet[ethernet shield or pc] and keeps checking for specific mails requesting sensor data / requiring control action. I'm struck on detecting the base station - :-/
and need some ideas..
Classic way to do it (same method as the Roomba, but has been used by hobbyist robotics for 30+ years, likely) - is an IR beacon. Send a signal to turn it on, and have your robot look for it via a directional IR sensor (of some sort) and drive toward it. Once you get to the dock, the next issue to conquer will be docking (I am assuming the base station is mainly for recharging?)...
I wanted to do the IR thing to my wifitank too, and when it is close enough, then switch to line follower, and follow some lines drawn on the plate, all leading into the charger. When it then gets close enough, the walls on each side of the charger will guide it perfectly in.... Or, in my head this totally works ;D
Thanks Crash! Can you tell me more on how the Ir beacon works, what kind of directional ir sensors are we talking about? and in general, how can we sense the intensity of the ir?[without confusing it with ir from the sunlight / other sources?]
If the intensity can be measured, then it becomes easier. mount a the ir intensity sensor on the robot on top of a 360degree servo. keep moving the servo to determine the direction with the most intense signal and move towards it.
Can you tell me more on how the Ir beacon works, what kind of directional ir sensors are we talking about?
Well, if you modulate it like you would for a remote control (38-40 kHz or thereabouts), then you can look for that modulation. You might also put an IR filter in front of the phototransistor detector (classic way to get such a filter was to expose a piece of black and white film, then have it developed, and use the negative - IIRC).
Another thing to do would be to put an IR opaque tube around the sensor, to make it more "directional" (with maybe a lens at the end). You could make the sensor using 8 or 16 IR phototransistors in a radial pattern (instead of a mechanical system).
The beacon is basically the same - a bunch of IR LEDs and a driver arranged in such a manner to throw the IR signal in an omni-directional pattern...
You could use something like this Pololu IR Beacon Transceiver ( or make one ) and then use the line following idea it worked for me ( i used laser and ldr )
Well, if you modulate it like you would for a remote control (38-40 kHz or thereabouts), then you can look for that modulation. You might also put an IR filter in front of the phototransistor detector (classic way to get such a filter was to expose a piece of black and white film, then have it developed, and use the negative - IIRC).
I get all of this... what i dont seem to understand is how you measure the intensity of the signal? for example will a modulated remote signal have the same duration for marks & spaces at all distances from the source?