Anyone on here know about PIC chips?
Discussion
Hi all,
Just working on a university project to build a variable length induction system for a formula SAE car. Anyway, to make the thing actually move, my plan is to use a high speed stepper type actuator to slide the primary pipes the 7cm or so that they need. Now I haven't done much research into the motor yet(I'll get onto it this week), but as far as I can tell, I'm going to need a varying 0-5v signal corresponding to 0v = min height, 5v = max.
The reference signal will be taken from the crank sensor which I'm guessing gives a 12v pulse each time a tooth is seen. So what I need to do is create a system which can read the output from the crank sensor and convert it into a 0-5v signal, ideally using some sort of lookup table so I can alter the height for a given engine speed. The ultimate goal is to run the car on the dyno and for several points on the power curve, find the optimum trumpet length for maximum resonant tuning and then put this into a table. This table would then alter the trumpet length in real time to optimise both mid range torque and top end power.
I'm just trying to think of the best way of doing this and as far as I can tell, a PIC chip system would be best. I have never used a PIC chip before though so I'm not sure if they are capable of this type of application. Before I do a little more digging, has anyone here got any experience with these? Would this work or should I be looking somewhere else?
Cheers,
Nick
Just working on a university project to build a variable length induction system for a formula SAE car. Anyway, to make the thing actually move, my plan is to use a high speed stepper type actuator to slide the primary pipes the 7cm or so that they need. Now I haven't done much research into the motor yet(I'll get onto it this week), but as far as I can tell, I'm going to need a varying 0-5v signal corresponding to 0v = min height, 5v = max.
The reference signal will be taken from the crank sensor which I'm guessing gives a 12v pulse each time a tooth is seen. So what I need to do is create a system which can read the output from the crank sensor and convert it into a 0-5v signal, ideally using some sort of lookup table so I can alter the height for a given engine speed. The ultimate goal is to run the car on the dyno and for several points on the power curve, find the optimum trumpet length for maximum resonant tuning and then put this into a table. This table would then alter the trumpet length in real time to optimise both mid range torque and top end power.
I'm just trying to think of the best way of doing this and as far as I can tell, a PIC chip system would be best. I have never used a PIC chip before though so I'm not sure if they are capable of this type of application. Before I do a little more digging, has anyone here got any experience with these? Would this work or should I be looking somewhere else?
Cheers,
Nick
http://www.national.com/an/AN/AN-162.pdf
Have a look through that, what you need is a frequency to voltage convertor, and those simple circuits should do that somewhere.
Have a look through that, what you need is a frequency to voltage convertor, and those simple circuits should do that somewhere.
>Sheepishly raises hand<
Yep, I have quite a bit of experience with embedded systems like this. A PIC based system is probably a good place to start in a fairly simple system like this. Although, having said that, if you have access to a more powerful micro, such as something including an ARM based chip, that would allow you to use a high level language such as C or C++. If you haven't done any assembler programming before, it can be rather daunting. The great thing about PIC micros is that you can pop them in a universal prototype breadboard and play around with them there. They are also extremely cheap and robust. I haven't had a PIC fail on me yet, despite quite a lot of electrical abuse.
Yep, I have quite a bit of experience with embedded systems like this. A PIC based system is probably a good place to start in a fairly simple system like this. Although, having said that, if you have access to a more powerful micro, such as something including an ARM based chip, that would allow you to use a high level language such as C or C++. If you haven't done any assembler programming before, it can be rather daunting. The great thing about PIC micros is that you can pop them in a universal prototype breadboard and play around with them there. They are also extremely cheap and robust. I haven't had a PIC fail on me yet, despite quite a lot of electrical abuse.
Zad said:
>Sheepishly raises hand<
Yep, I have quite a bit of experience with embedded systems like this. A PIC based system is probably a good place to start in a fairly simple system like this. Although, having said that, if you have access to a more powerful micro, such as something including an ARM based chip, that would allow you to use a high level language such as C or C++. If you haven't done any assembler programming before, it can be rather daunting. The great thing about PIC micros is that you can pop them in a universal prototype breadboard and play around with them there. They are also extremely cheap and robust. I haven't had a PIC fail on me yet, despite quite a lot of electrical abuse.
Just because it can be done by a risc processor doesn't mean it should be, especially when a f to V convertor chip will do exactly what's required.Yep, I have quite a bit of experience with embedded systems like this. A PIC based system is probably a good place to start in a fairly simple system like this. Although, having said that, if you have access to a more powerful micro, such as something including an ARM based chip, that would allow you to use a high level language such as C or C++. If you haven't done any assembler programming before, it can be rather daunting. The great thing about PIC micros is that you can pop them in a universal prototype breadboard and play around with them there. They are also extremely cheap and robust. I haven't had a PIC fail on me yet, despite quite a lot of electrical abuse.
Or as a compromise look into using a Basic Stamp.
They're a programmable chip but they're programmed using basic so a doddle to get started with.
With a simple application like yours, should be a piece of....
http://www.parallax.com/tabid/295/Default.aspx
Yes I'm a geek.
They're a programmable chip but they're programmed using basic so a doddle to get started with.
With a simple application like yours, should be a piece of....
http://www.parallax.com/tabid/295/Default.aspx
Yes I'm a geek.
Infinitely variable might be a bit overkill? gut feeling is that you won't see massive improvements vs. a two step system a-la toyota ACIS, not for the hassle involved anyway. Manufacturers don't generaly do it so there's probably a reason for that - sorry to be on a downer about it! It is interesting stuff never the less.
buggalugs said:
Infinitely variable might be a bit overkill? gut feeling is that you won't see massive improvements vs. a two step system a-la toyota ACIS, not for the hassle involved anyway. Manufacturers don't generaly do it so there's probably a reason for that - sorry to be on a downer about it! It is interesting stuff never the less.
That's why it's a Uni project for a race car.Pretty much everything in an engine is a compromise somewhere, and it is quite a simple project.
From what i gather, the true length for a resonating intake is massive, and the ones you see are actually 1/4 wave resonators.
What would be a clever idea is some sort of small package variable length intake , which i suppose would be spiral telescoping tubes in a large airbox, otherwise you'll have runners poking out the side of the engine!
spikeyhead said:
Just because it can be done by a risc processor doesn't mean it should be, especially when a f to V convertor chip will do exactly what's required.
Fine if you just want a voltage proportional to the frequency. You need to process that to activate the inlets though (a lookup table was mentioned). You might also want to make into account things like throttle opening, air mass flow etc. If you are doing that with a micro then you might as well skip the F-to-V and sense it with the micro. Lecturers like to see a nod towards total cost and whilst software development seems expensive, PIC16s start at 39 cents each in 1000qty. Even ARM7s from Freescale etc are only around $2:80. Doing it with analogue components tends to be the expensive way.Maplin used to do this as a little kit - but anyhows, one of these, plus some triming components to adjust for speed should do the trick. K.I.S.S. ...
http://www.maplin.co.uk/module.aspx?moduleno=2470
http://www.maplin.co.uk/module.aspx?moduleno=2470
Wow thanks for the quick replies guys, amazing how much specialist knowledge is present on this site. I thin the nice simple PIC systems look like the sort of thing I'm looking for as I haven't any experience with this at all. I have seen quite a few of the two stage systems and it is something I'm looking as as this system is used on the Yamaha R1 bike which is very similar to the engine I'm working on (R6). I'm aware that the gains won't be huge, but the point of the project is to prove that resonant tuning does work. If I can, I'd like to go for the infinitely variable system, just so I have plenty of variables to play with, but if its going to be too tricky then I could go for a simple switch system when the crank sensor freq reaches a certain preset value and have a two step system.
I'm just doing the groundwork for the electronic bit so I'll see what's realistic and what isn't in this case. The PIC stuff looks most realistic, though I'm not really sure I'm capable of programing it to do what I want it to do. I'm sure we have PIC programming software and chips at University so if I can figure out how to make a program then I'm set. The pdf posted looks like a good place to start - thanks for that! Best get reading before I ask any more questions...
I'm just doing the groundwork for the electronic bit so I'll see what's realistic and what isn't in this case. The PIC stuff looks most realistic, though I'm not really sure I'm capable of programing it to do what I want it to do. I'm sure we have PIC programming software and chips at University so if I can figure out how to make a program then I'm set. The pdf posted looks like a good place to start - thanks for that! Best get reading before I ask any more questions...
TheEnd said:
buggalugs said:
Infinitely variable might be a bit overkill? gut feeling is that you won't see massive improvements vs. a two step system a-la toyota ACIS, not for the hassle involved anyway. Manufacturers don't generaly do it so there's probably a reason for that - sorry to be on a downer about it! It is interesting stuff never the less.
That's why it's a Uni project for a race car.Pretty much everything in an engine is a compromise somewhere, and it is quite a simple project.
From what i gather, the true length for a resonating intake is massive, and the ones you see are actually 1/4 wave resonators.
What would be a clever idea is some sort of small package variable length intake , which i suppose would be spiral telescoping tubes in a large airbox, otherwise you'll have runners poking out the side of the engine!
Then again I don't really know what the actual rules of f.s.a.e are....
hi there,
interesting little project. I have considered using a membrane stretched over sprung trumpet. for infenatly veraible system that is nice and smoth for air flow. also you might want difrent lengths for each inlet
a pic would be a good for this type of project a 16 or better still 18 series would provide all the IO you would need for this and controlling other stuff as well. i.e. rule dependant gear change / traction / stability or just the dash or what ever else you feel like controlling.
if you do do with the PIC mack sure that you add an RS232 port to the device then you will be able to use a boot loader.
there is also a C compiler if asembaly is scaring you off witch I think is free for educational use.
if you felt like going over kill you could ues a DS series for some funky number crunching at the end of the day there are a number of low cost devises out there you are best off going with what ever you have support for in your department. or pop over to electrical engendering and see what they have
ceebmoj
interesting little project. I have considered using a membrane stretched over sprung trumpet. for infenatly veraible system that is nice and smoth for air flow. also you might want difrent lengths for each inlet
a pic would be a good for this type of project a 16 or better still 18 series would provide all the IO you would need for this and controlling other stuff as well. i.e. rule dependant gear change / traction / stability or just the dash or what ever else you feel like controlling.
if you do do with the PIC mack sure that you add an RS232 port to the device then you will be able to use a boot loader.
there is also a C compiler if asembaly is scaring you off witch I think is free for educational use.
if you felt like going over kill you could ues a DS series for some funky number crunching at the end of the day there are a number of low cost devises out there you are best off going with what ever you have support for in your department. or pop over to electrical engendering and see what they have
ceebmoj
The reason is that the fsae events require power all the way across the powerband. Some events favour top end stuff whereas the handling course/acceleration test etc requires as much torque as possible. Usually the car is tuned to a compromise but I aim to get the best of both. As has been said though, the true resonator length for the engine is around 1 metre from 0-18k revs so I will be picking a smaller band of around 6k to 12-13k as this is the most frequently used band. This should see some gains over around a 10cm adjustable length trumpet which I'm building into a telescopic type setup.
Edit: Thanks very much for the offer Adrian, I may have to take you up on that! I'll go and have a chat with the elec engineers tomorrow and see what they come up with...
In case anyone is interested, this is a (very vague) idea of what the system will look like. It's way off completion but this is the basic model I've been using to flow test. As you can see, its not done yet as cylinder 1 is getting less air than 4 in this pic. The problem is that the car has to run a 20mm restrictor which has the habit of turning the inlet air into a supersonic jet. This plenum is trying to diffuse it yet not impede flow
Edit: Thanks very much for the offer Adrian, I may have to take you up on that! I'll go and have a chat with the elec engineers tomorrow and see what they come up with...
In case anyone is interested, this is a (very vague) idea of what the system will look like. It's way off completion but this is the basic model I've been using to flow test. As you can see, its not done yet as cylinder 1 is getting less air than 4 in this pic. The problem is that the car has to run a 20mm restrictor which has the habit of turning the inlet air into a supersonic jet. This plenum is trying to diffuse it yet not impede flow
Edited by 450Nick on Sunday 1st February 21:25
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