Re: microcontroller for rocket.
 

I have to agree with Cdeaver that the eletronics are going to a little bit complicated but it can be done. You have to spend some time testing. The pic Microchips have a couple A/D converters(analog to digial) with 10 bit resolution and so they are more than capable and I have a working servo code.
If you guys can use servos to open the shute then it can be done.

As Gdeaver was saying you need to figure out what pressure you need to deploy the rest is in the data sheets and programming. I haven't played with the A/D converter but I don't think they are hard to work with. Once the code is set up the only thing that will probably need to edit the the 10 bit value (0 to 1024) to get the precise altitude. What you are planning to do should not demand much form the pic at all. I can get you guys set up with a simple circuit. The servos signal wire can be directly connected to the Microchip via a 220 Ohm resistor.

You are going to need:
A Pic Microchip (any can do it but the 18 series can be programmed in C)
MpLab IDE (microchip.com) FREE
C18 compiler(microchip.com)FREE
28 or 40 pin socket (depending on the pic) Radio Shack
IC-Prog (icporg.com) FREE
A male serial plug(for the programmer in http://www.picbasic.co.uk/forum/arc....php/t-703.html )Radio Shack
4.7k Ohm, 220 Ohm, and the whatever is needed for the pressure sensor
resistors. Radio Shack
5+ voltage regulatro Radio Shack
.1 uF capacitor (metal film? i am not sure) Radio Shack
9V battery and connector Radio Shack
The pressure sensor(internet?) and whatever components its circuit needs(Radio Shack)

What is your DEAD LINE?

Re: microcontroller for rocket.
 

Wow, thanks so much for the help. The Deadline is April.

The question is whether or not they'll get that far with it, while doing FIRST at the same time. Like I said I think they have a good fall-back plan. But we'll try to do the electronics bay - which will really make it cool.

Most of the items don't seem to expensive, even the C18 controller is only like $9 at DigiKey. I'm not sure about the barometric pressure sensor (which may be the most expensive). But won't it still require a separate component for programming the PIC, or is it as simple as hooking it up to the correct pinout on a that serial port?

Re: microcontroller for rocket.
 

I was thinking about just finding out the voltage/pressure that would equal the altitutde of chute deployment.
I'm not exactly sure how the sensor works, but would we be able to set an initial pressure (when the rockets on the ground) and then the reading by the sensor would be the same regardless of distance from sea-level.

only thing is that air pressure vs. altitude follows a non linear curve ... so i'm not sure how a sensor would be able to "tare" itself


EDIT: the precision we are looking for is about +- .1 sec for flight time and +-1ft in height. :rolleyes: lol

Something tells me we should be worrying more about rocket stability...

Re: microcontroller for rocket.
 

There is no C18 controller but a C18 compiler which is a C compiler for the 18 series pic Microchips. It is free off the website.
Yea with the resistors, that programmer works, i have used it. The particular software allows it to work with minimal hardware. There are programmers out there for the pics but this one amazingly works and is very very cheap.

In the pin Diagrams for the partiqular pics in the Data Sheets:

DATA = PGD pin
Clock = PGC pin
_____
MCLR or Vpp = MCLR/Vpp pin

Depeding on the pic you have to pull the PGM pin to ground during programming.


What exacly is the flight time, for lauch to touch down?
The processor is fast enough to do it but I don't know if the sensor can do such precision (+- 1ft is going to be hard). Could you explain this and other technical componets of the competion in a little more detail?

I would have to read the Data Sheets to figure out the voltage/pressure ratio.(This might help: http://www.geocities.com/SiliconVal.../altimeter.html)
You are right it is quite pricy at around $30. This sensor just might not be accurate enough. You need like a low altitude one.
I know about the pics not the pressure sensors.