LeeM
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Registered: 26th Sep 05
Location: Liverpool
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I need to build a solar powered car, only small and basic and doesn't need to follow a track just drive a set distance and stop within a range.
I was thinking of using one of these small circuit boards but I can't remember what they're called, running a basic code etc but I'm in the very early stages of the research so have no idea what I'm doing yet 
Anyone got any helpful suggestions?
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adiohead
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Registered: 28th Sep 01
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Could you not get an already made battery powered remote control car and convert it?
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John
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Registered: 30th Jun 03
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Do you mean Arduino, that would probably do what you want, there will also be loads of code examples if not that exact thing.
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ed
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Registered: 10th Sep 03
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You can even get a solar shield battery charger for Arduino.
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
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Arduino that's the one, thanks John. now ed does that run it directly from solar power or do I plug a battery into the board and then the solar panel into the battery? I was hoping there would be something along those lines for the Arduino, seems to be a lot of potential with it
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
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quote:
Originally posted by adiohead
Could you not get an already made battery powered remote control car and convert it?
It's a Uni project, that would be cheating
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ed
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Registered: 10th Sep 03
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You'd want a battery ideally as if your control board looses power it'll shut down. Is there a requirement for your project to only use solar? The Solar Shield lets you connect a panel and a lithium battery together, it charges the battery and will power your board. You then just need a motor controller (something like an L293D board) and you're away.
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ed
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Registered: 10th Sep 03
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http://shieldlist.org/seeedstudio/solarcharger
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
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That great cheers ed, I'll be getting a full spec sheet later on today just trying to do the groundwork
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Dom
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Registered: 13th Sep 03
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Do you need an Arduino? As it sounds like the car just needs to travel in a straight line for X metres. Which case a simple motor, battery solar charge setup with a simple timer would do the trick. Obviously if needs intelligence of sorts then an Arduino (or an eBay copy which is about half the price) would be suited.
As for the solar charger, a solar cell and diode would do the job (wouldn't be suitable for lithium batteries though).
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
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I want it to stand out as innovative rather than a simple timer
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ed
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Registered: 10th Sep 03
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Just make sure the thing works at the end of your assignment! In a class I taught last year the students needed to make a robot that solved a maze, there were a few over ambitious groups who attempted to use ultrasonic sensors and other things to make their work stand out. Would have been bloody brilliant if they did something more than just spin around in circles on one spot...
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
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yeah there is that
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
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Had a 555 timer suggested. It only needs to go 10 meters in less than 20s
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John
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Registered: 30th Jun 03
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Does it have to stop after 10 meters or just go 10 meters?
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
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10 meters in a straight line, come to a dead stop after that. Doesn't specify a stopping distance but I imagine the shorter the better.
If I use batteries I can only use 3 aa's and the supplied 6v 250mA solar panel...
[Edited on 17-01-2012 by LeeM]
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John
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Registered: 30th Jun 03
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What about using a capacitor?
Get one just the right size to give you 10 metres, would be really simple.
Depends what the learning outcomes are.
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
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Can use a capacitor yeah, we're being encouraged to go outside of the spec, but there's certain things we can't change
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John
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Registered: 30th Jun 03
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Solar panel either charges capacitor directly or charges a battery that you then use to charge capacitor.
Switch it on, place it down, runs out of power just before the 10m mark.
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ed
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Registered: 10th Sep 03
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Capacitor could be pretty accurate too actually. You'd need to experiment a little to get the right amount of charge, perhaps you could make the chassis using the PCB/stripboard to save some weight.
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LeeM
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Registered: 26th Sep 05
Location: Liverpool
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I wanted to have a look into a sheet of carbon. Got to be a max of 200mm long but not sure how much that would cost
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Ian
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Registered: 28th Aug 99
Location: Liverpool
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Couldn't you build a tunnel on the finish line?
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adiohead
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Registered: 28th Sep 01
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quote:
Originally posted by Ian
Couldn't you build a tunnel on the finish line?
or a wall
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Ian
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Registered: 28th Aug 99
Location: Liverpool
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You could do distance without an Arduino, you need a pulse from the wheel/transmission and you need to calculate how many pulses equals your distance, then use a binary counter to track the pulses with a not gate on the most significant bit in series with your motor supply.
Have a look at the counters section here - http://www.kpsec.freeuk.com/counting.htm
Uses a 555 to stabilise the pulse and a binary counter, not sure what chip for that, you just need to calibrate your gearing so the distance is achieved in of 2^n pulses for any value of n.
If you wanted to be a bit more flash you could use a series of ANDs across the entire binary word so give you a configurable value at which you isolate the motor, like if the binary counter gets up to 100101, you go a.not b.not c.d.not e.f is true with that value is met, not that and you'll have a value that goes to zero when the desired distance is met.
You would also need to isolate the counter after that point as well somehow so it doesn't continue past and re-engage the motor because that truth condition is no longer met due to momentum.
Edit - think you can count in binary just using a chain of bistable 555s, think you can get another chip which is built with that in mind and has integrated output/trigger in the chain, although this would be more difficult to get your distance number out of if you're going for the non 2^n solution.
[Edited on 17-01-2012 by Ian]
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Ian
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Registered: 28th Aug 99
Location: Liverpool
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Just looking there if you assume an 8 bit word, 10 metres / 128 is 7.81 cm
So you take the pulse from the axle you need wheels with a circumference of 7.81cm work the diameter back from that using c=2 PI r
If that comes out too small then go down to a 7 bit word and if that's too big then get the pulse from somewhere in the gearing as you will probably need to step it down if you have a high speed motor with insufficient torque.
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