Hi, I’m the author of these papers: http://www.epokh.org/blog/?page_id=11
I would like to use the 3pi robot but i need some additional sensors\emitters.
The experiment set up is as follows:
a flat playground with walls, white floor with colored circular blobs (circular shape, let’s say black but i need also to detect different colors).
Every robot has a left and right input.s
A couple facing down to detect food blobs.
A couple facing front to detect other agents lights.
Every robot produces an omnidirectional light source (one of this colors red, green and blue at a time) : ideally should be a a triplet ring of connected LED. So that i can choose to produce every time 1 omnidirectional colored light
A couple facing front to detect proximity objects: capacity sensors or Ir sensors for obstacle avoidance.
I know it looks like an epuck agent but your robot is cheaper so if I can manually add this feature I’m happy to buy it.
Hello,
I’ve never used an e-puck, but from what I can see, the e-puck and 3pi are quite different robots - I think the e-puck is designed for high-level applications involving image processing, since it features the dsPIC and its main sensor is the color camera. The 3pi is designed more for low-level programming where raw speed and performance are important; its top speed is about 8 times faster than the e-puck, and it can make more than 5000 sensor readings per second (5 sensors at 1 kHz). The 3pi also has no odometry, though its motor speeds are consistent enough for some amount of navigation. Make sure you consider these issues when choosing a robot.
With 3pi, we’ve focused on the line sensors only, so that we could do them as well as possible, but we left a little bit of room for you to add extra sensors. Take a look at the pin assignment table for detailed information about what ports are available for your use. The simplest way to start is by removing all of the optional jumpers - you can then get access to three extra analog inputs, without losing any of the line sensors. Two digital ports are also available for more advanced expansions - these can be used as serial communication lines to talk to a second microcontroller. So you could put a more advanced processor, with a color camera or whatever else you want, on top of the 3pi. For example, you could put a CMUcam3 on top, using its ARM7 processor as your main controller, and program the 3pi to be a “dumb” base that is drives in response to commands from the ARM7. The total cost would still be less than half of the e-puck.
For your specific application, I don’t know of anything simpler than a color camera that would work - but did you have some kind of simpler color sensor in mind? If you don’t want to go with a camera, I’d recommend taking colors our of your environment. For example, the different LED colors could be replaced by IR LEDs modulated at different frequencies. You might be able to use our IR beacon development board for this purpose, but it’s definitely tricky to get this solution working well in a noisy environment with many robots! The multi-colored blobs on the floor could be replaced by black blobs of different sizes or shapes; 3pi should be able to distinguish a solid circle from a circular ring.
Anyway, this sounds like a fun project. Please let us know how it goes - I’d be happy to hear more about it, whether or not you use the 3pi!
-Paul
Hi thanx for the detailed reply.
Yes the epuck is for intense processing but I need more reactive agents and I don’t care about navigation.
I would like to avoid the camera solution because they should be like simple insects (antennas like sensors).
For my old lego project I used CDS light sensors but of course they need to be connected to an ADC port.
I was thinking about changing the light with sound: i.e. using a PWM audio generator, but I need to exchange the buzzer with a proper speaker.
About the inputs to use: since i only need PC0 and PC4 but not PC1,PC2,PC3 are free but they are analog inputs right? The reflectance sensor works as on\off?
The problem of my project is that i need to use a lot of agents: starting from 10 and adding new ones progressively, so buying 40-50 epucks is not a cheap economical solution.
P.S.
I’m waiting my department approval for expenses than i can order one and start to play.
Hello,
Did you manage to use the CDS sensors as color sensors? I know that you can get them with some amount of color sensitivity, but I think it would be very hard to actually tell the difference between, say, green and red blobs, without some kind of filters.
PC1, PC2, and PC3 are used for the middle three sensors on the robot, so they are not free, but you could “free” them by de-soldering the resistors like R13 (see schematic) to disconnect the sensor. Are you sure you don’t need them? Anyway, they are general purpose I/O pins usable as digital inputs or outputs, or as analog inputs.
The sensors are used with the pins configured in digital input mode, but they actually act as analog sensors - the RC circuit around each sensor allows the digital port to act like a simple analog-to-digital converter. See our application note on the QTR-RC sensors for an explanation.
Well, I guess that description wasn’t quite as clear as it should have been. I’ve fixed it up a bit. Product #747 includes the programmer and a USB cable, and the Product #975 is just the 3pi alone.
You are welcome to order directly from our site, and you can preview the shipping charges by adding items to your cart and starting the checkout process. It looks like the cheapest shipping option for a 3pi to the UK is about $15. If you are planning to order a lot more later, it would be a good idea to let your local distributors know that you are interested in buying it through them - there is a chance that they would be able to help you save on shipping.
