Just done some quite extensive research and can't make up my mind as to what to use.
The project:
A fairly small (about 14cm long and only 4cm wide) model bus has to SMOOTHLY navigate around a basically rectangular course (with rounded corners).
I looked into IR, ultrasonic, IMUs and even GPS and they all don't quite hit the spot.
I'll probably only have room for an Arduino Nano inside, plus all the driving hardware and a Li battery, so that makes things even more interesting.
I'm currently looking at putting IR leds at the end of each straight and then programming for a smooth 90 degree turn to latch onto the next IR led when a certain distance away. Seems sort of sloppy though and it would be nice if sometime in the future it could find it's way on a different sort of course.
Also, it would be really nice if I could program in bus stops and docking at a recharge station.
Yeah, I know, not wanting much am I.
So any ideas, help etc. are going to be VERY welcome.
Have you come across the Faller car system. It is steered using small magnets that follow an iron wire laid into the roadway. Does not need any microprocessor.
The only alternative that I can think of is a line-following system wth a white line painted on the surface to denote the path to follow,
I suspect that only having reference points at the corners would not be sufficient to keep the car on track after a turn. It would also be difficult to ensure the turn was the correct number of degrees.
Hi,
Thanks for that link Robin2. The line following idea had occurred to me but not in as simple a form as that.
BUT it doesn't use Arduino and lacks flexibility. Although I may yet end up with something like that.
In that case I'd still put a Nano in, let it decide when to pull into a bus stop or not and smooth out the motion etc.
And Tom, nice to hear from you again. (You helped a lot with my "cable car"project). You put your finger on the problem. WHAT am I going to use to guide it.
I don't want an obstacle avoidance setup, too jerky.
I'd be quite happy to use IR "beacons" but not sure how straight a line that would produce (ambient interference etc.).
Or ultrasonic, but that would imply a wall or such to follow, don't have that.
IMUs??? Each lap it would have to re-initialize to correct errors creeping in and wouldn't allow for bus stop detours etc. etc.
Decisions, decisions, decisions. Well, not really. More lack of knowledge really.
What about a combination of line following and a Hall effect sensor. You can embed small magnets in the track which can optionally trigger the bus pulling in.
BUT it doesn't use Arduino and lacks flexibility
You can make. An optical line follower using an Arduino. You could even have a colour sensor to sense the changing colour of the line to trigger other options / possibilities.
Decisions, decisions, decisions
Often the hard part, the mistake beginners often make is trying to do too much at once. Start simple and then add complexity.
Thanks for that Grumpy_Mike.
What do you think of an IR Led at the end of each straight. At the preset distance it turns (Australia, so always to the right) until it spots the next beacon and homes on that etc. etc.
The attraction is that the beacons aren't visible. For bus stops/detours, switch the next beacon off and switch on one at an angle to the progress. As soon as it orients on that, run a small prog to complete the stop and rejoin the track, focusing once again on the end beacon
Too complex? Should I go with the Faller idea? What is your view?
Grumpy_Mike:
What about a combination of line following and a Hall effect sensor. You can embed small magnets in the track which can optionally trigger the bus pulling in.
I think the Faller system can do that. I have certainly seen some very realistic OO scale road models working alongside model railways.
And, with a bit more space and an Arduino it should be possible to implement some very fancy moves. What about a 3-point turn?
Indeed with an Attiny 1634 you can get a lot of computing power in a small space while still being able to do hand-soldering.
What do you think of an IR Led at the end of each straight. At the preset distance it turns (Australia, so always to the right) until it spots the next beacon and homes on that etc. etc.
That is. It going to be smooth is it? Which I thought was one of your criteria.
Hi,
Thanks for all the responses.
I am now starting to think along the lines of the Faller system, copying the turn-off system with electro magnets etc. and augmenting it with an Arduino to control the motors, allowing smooth stopping/starting as well as using a servo for the steering, making that smoother. As in, the wire follower inputs a signal to the Arduino which then does the actual steering.
And yes, getting the bus to do a 3 point turn somewhere (and self park for charging) sounds real cool.
Well, looks like the job is done.
All that remains now is source the bits, build the hardware, write and debug the code. Piece of cake!
But seriously, anything else comes to mind to make things easier or simpler or fancier or just plain more fun, please speak up.
"How about a line-follower, with the line drawn in invisible UV marker pen, using a couple of UV LEDs?"
Great idea!! Will an IR line and 2 LEDs be enough to take reasonably tight corners? And is there any existing code to do it? (Yes, I know. I'm lazy).
It could still be combined with magnets/reed switch for bus stops, traffic lights etc.
QUESTION: It would have to be drawn on a black paint surface. Will it fluoresce enough to pick up reliably and would the LEDs have to be a specific wavelength????
