Electric Vehicle C

[fleet130]

I always thought that working with microprocessors was one of the main purposes of the electric vehicle event.

Just the opposite is true. It has been a struggle to prevent them from being banned. Microprocessors are viewed by many as an unfair advantage due to their "excessive" cost. They complain that a team with big bucks can just buy a microprocessor and off the shelf software, plug it into their vehicle and magically get a perfect score every time without having to do any work.(I make no claim this has a basis in reality).

assuming the mechanical bonus really materializes in the final rules, does anyone have any idea how much of a bonus there is?

The proposed bonus was 1/3 the difference between 200 and the final score if the vehicle doesn't use any electronics. Note that as the error approaches zero, so does the bonus! I don't have the final rules, but, to my knowledge, it hasn't changed. Can anyone confirm that?

[WrightStuffMonster]

I am pretty sure that you can get a everything you need to program an Atmel including the chip for around 15-20 bucks if you shop around. Sparkfun sells everything that you need to get started for somewhere around that. That is a weeks worth of coffees for your average teenager. If you can not afford you spend 15 for a micro you probably have some fairly serious issues with your ev. I would love to see that off the shelf software that allows ev to be a plug in and play affair. I have never seen anything like it. Thanks fleet for dealing fighting to keep micros in. That was by far the most educational part of the event was learning how to program micros well enough to make the ev go.

[Dark Sabre]

I always thought that working with microprocessors was one of the main purposes of the electric vehicle event.

Just the opposite is true. It has been a struggle to prevent them from being banned. Microprocessors are viewed by many as an unfair advantage due to their "excessive" cost. They complain that a team with big bucks can just buy a microprocessor and off the shelf software, plug it into their vehicle and magically get a perfect score every time without having to do any work.(I make no claim this has a basis in reality).

assuming the mechanical bonus really materializes in the final rules, does anyone have any idea how much of a bonus there is?

The proposed bonus was 1/3 the difference between 200 and the final score if the vehicle doesn't use any electronics. Note that as the error approaches zero, so does the bonus! I don't have the final rules, but, to my knowledge, it hasn't changed. Can anyone confirm that?

That is the correct calculation. The run scores are both based off of Distance Score + Time Score + Finish Line Score + Center Line Score + Bonus Score (which, if present, is calculated based on the sum of the first 4 scores).

[andrewwski]

That bonus seems fair...if you do good it won't depend on the type of vehicle.

But using electronics isn't necessarily expensive...I did a timer for less than $30...

[gh]

I am pretty sure that you can get a everything you need to program an Atmel including the chip for around 15-20 bucks if you shop around. Sparkfun sells everything that you need to get started for somewhere around that. That is a weeks worth of coffees for your average teenager. If you can not afford you spend 15 for a micro you probably have some fairly serious issues with your ev. I would love to see that off the shelf software that allows ev to be a plug in and play affair. I have never seen anything like it. Thanks fleet for dealing fighting to keep micros in. That was by far the most educational part of the event was learning how to program micros well enough to make the ev go.

This is true, but remember that you do need an optical encoder to interface the vehicle with the microcontroller, and a good encoder is not cheap. However, the Vex robotics franchise (I think I'll call it that from now on) sells reasonably good encoders, and you can get $400 industrial precision encoders used from eBay for under $20, which is what I did.

You also need some way of driving motors with the micro. This can be had for a few cents in MOSFETs, or could run up more than $50 if you buy a dedicated motor controller. I feel that modifying a $20 servo to continuously rotate (Google "continuous servo" for tutorials) is the best tradeoff in price vs. performance. That $20 will buy a self-enclosed, relatively tough gearbox and motor, with its own internal motor driver that can provide simple but precise speed adjustments, as well as braking.

Finally, throw in about 50 hours of programming, and twice as much time testing, and you might have a winning vehicle. My EV last year was pretty minimal, compared to the stuff I listed here. A lot of the stuff was surplus or free samples. Spending lots of money will save time, but spending money will not help you win.

Anyways, I usually justify my SO expenses to my parents by reminding them that I don't have a cell phone or video game console, and I haven't gone to the mall in years. Those are teenager stuff, right?

[jander14indoor]

OK, so how do you interface with those cheap electronics? If you say laptop or palm device BZZZZzzzzzzt, the cheap 20 dollars of electronics on your vehicle just went to $220 to $520 minimum and THAT's the expense of concern.

Note, I don't think there's anything WRONG about the approches you guys are discussing, they are all valid ways to learn about science and technology. And trying to save money can be a BIG driver of innovation. But, you should understand the rest of the story.

One of the percieved (and probably real) issues with SO is lack of participation by disadvantaged schools and students. Here in MI we have regular debates on the state board about allowing the use of computers at any event. My local region (region 8, Wayne Co) includes areas ranging from the most impoverished areas of Detroit to some of Michigans wealthiest suburbs. For some schools even the entry fee is challenging so we've established grants to recruit them. But computers at such schools are RARE and not widely available for uses such as this.

The rule you see is partly an offspring of this issue. It is there to encourage those without access to computers to compete without at least the perceived barrier of lack of resources.

Hope that helps understand how the bonus came about, I'm still curious to see both the mechanical solutions AND the cheap electronic ones.

Jeff Anderson
Livonia, MI

[andrewwski]

It's really a shame that some schools don't even have computers. Our schools is far from a rich school...but we have computers everywhere. It shouldn't be a problem to find one computer to use for competition, but I suppose it is in some places.

Maybe they could ban using computers in the competition? Then, you could use a microcontroller programmed by any computer (not necessary to be present at competition site) with some kind of input to set distance.

Or, in my case, a timer works well enough. And I don't even need a computer to set it. It's only composed of a few logic gates and stuff.

[sachleen]

you dont need a computer. if you have a microcontroller, you can setup a system with switches that increase/decrease the distance the car needs to travel. Before someone donated a old laptop to me I did it with a button. every push increased the distance by 5 pulses, then I had another button that increased it by 1 pulse (pulse of the encoder, 90 pulses per revolution) I also had a 7segment LED on it that would read out the time that it took to travel the distance while testing the car.

see, no laptop needed but it sure makes life a whole lot easier. Also, if you have VEX, there's a PALM thing that lets you download code to the controller from your PDA. You could find a PALM PDA on ebay really cheap i guess.. but you could also find a laptop really cheap there too

[gh]

First of all, the encoders and servos I mentioned can be interfaced with easily, as they use very simple digital signals (no messy voltages, mixed signals or super high speeds). I used the change-on-PORTB interrupt feature on a PIC I got for free to increment a counter every time an edge occured on the encoder's output line. I believe WSM used a very fast SX chip (not as cheap as my solution, but we're talking like $10 here) to poll the line for changes. Tehkubix used whatever Vex uses to read the Vex encoders, so he got off easy with a more encapsulated solution there. Well, Vex uses the 18F family of PICs, so it's not hard to guess how they did it. What actually goes on a vehicle is not out of reach of 90% of the teams. I speak of this as a student who used to be on a less than privileged team that couldn't afford to do several events and had to share a bus with another team to make it to states.

I can understand the concern about needing a computer to actually program the microcontrollers with. It is completely impossible to use a microcontroller without frequent access to a computer to work on. I didn't realize it was that bad.

On the other hand, it is not necessary to bring a computer to competition, if that is a more pressing concern. kube had a gold-winning vehicle that he operated with a button and a 7-segment he scrapped off of a broken motherboard. I didn't have a laptop, so I used a fancy screen and pushbuttons that I won in another competition. I may add that Uncle Fester's Div B nephew (if I recall correctly) was able to make his own electronic terminal for EV in a week, or something like that.

Now I'm going to get boiled alive for mentioning all of these people and their expert techniques. :)

[andrewwski]

I'm sure you can use a computer somewhere though. School, library, friend's house, etc.

But the way they then use "electronics" in general is too limiting...a simple timer circuit requires no microcontroller, and no computer access at all. Yet it uses electronics.