Newbie in need of help

stevertr

hey all. We're working on a HS physics project and need some help. This is as newbie as it gets because we're going to need to learn everything from scratch. I've tried reaching out to folks familiar with BS2 work here, and they're all "delighted to help" but so far haven't followed up so we're going to try and do it ourselves at least for starters.

Here's what we need to do. If you guys could at least tell us "what to purchase" for starters, we can get the items in hand while we wait for further help.

In short, we're doing a high altitude balloon research platform. We need a circuit board that will do the following:


A: We need it to activate 3 relays, each at specific times. One will activate the balloon cut down switch, one will turn on the audible horn, and one will cut the parachute cord. (the cut downs will be done by closing the circuit on a 9V battery through a piece of nichrome wire wrapped around the cord.

B: We need it to activate a tiny sirvo to close the payload bay door at a particular time.

For the items above, we need to be able to flip a switch on the outside of the device, to start the operation, and then have it automatically do X at 90 minutes, Y at 92 minutes, Z at 95 minutes etc...

C: We need it to log temperature and altitude on the flight using sensors that parallax sells.

i know that for you experts, this is all probably 6th grade robotics, but for us it's literally learning a new language.

If anyone can point us in the right direction, tell us what pieces to order, we'll get them here and take it from there.

Warmest regards

Steve

allanlane5

How heavy can it be? And how cold will it get?

Personally, I'd start with a BOE-Bot package. That has the AA battery pack I think you're going to need, a mounting frame, a Board Of Education (BOE), and a Basic Stamp 'plain' (BS2) which I believe is the lowest-power BS2 flavor.

Now, for timing, it depends on how accurate you need it to be. One approach is to do it "native" on the BS2 -- you'll need to code carefully to make sure it dooesn't gain or lose time based on what's running. A more accurate solution would be a 1607 time-chip with a coin-cell and timing crystal.

For relay-drivers, I find Darlington-Arrays work well, are small, and already have the 'snubber' diode built in. Plus they come in an IC of 8 darlingtons.

And you'll need one "Standard" servo -- the BOE-Bot comes with 2 servo's modified for continuous rotation. Oh, and you'll need the Parallax "Logging" module, or at the very least a 24L32 external eeprom to use for logging. Oh, and the temperature and altitude sensors.

allanlane5

Once you've built your first prototype on the BOE-board, you could get an inexpensive circuit card from Radio Shack and solder up a more permanent version. But use a socket for the BS2, you don't want to solder that into the circuit.

stevertr

Thanks for getting us started. Is there one that can use 9V? We want to use a 9V lithium cell because of the cold. Timing isn't critical as long as it's within a minute or so. Don't know what that array is, because I'm so new it's not even funny. What about relays? I see only two selections on the parallax site and they both seem to be only for high voltage.

Is one BS enough to do all that I need to do?

allanlane5

The BOE-Board has clips for a 9-volt battery, yes, so that can work. The problem is that relays can take quite a bit of current -- so you'll probably want *2* 9-volt batteries -- one to run the BS2, and one to run the relays and the "cutter" wire. Oh, and I believe a Darlington Array chip is like ULN2803.

You'll definitely want a 7.2 volt adapter, which you'll use to power the board during development. Then you can plug in the 9-volt lithium cell for flight. And yes, one BS2 (plus the other hardware) should be able to do all of this.

stevertr

Yes I'd assumed that one 9V would run the circuit board, open and close relays etc., but that a separate 9V battery would be used for each cutter wire. Still not sure what that Array chip is for, but then I'm pretty clueless. I just assumed that the BS would tell the relay to close at a certain time. What would the array do?

What does the 7.2v adapter do?

Ok so I'm going to order a BOE Board, and a BS2 or do I need one of the more advanced ones like the BS2sx or one of those?

How do I add the USB datalogger to it all?

Thanks again. Sorry to bother you guys with such elementary stuff.

stamptrol

Steve,

From your post, I understand you're new to the world of micros and electronics, but I'm afraid from your questions that you are expecting a purely "plug-and-play" solution to your project. It is unlikely that some shopping list will be presented which will magically assemble into the exact solution to your needs.

It would make sense to get the BS2, a few components and download "What's a Microcontroller?" from the Parallax site then have the team go through the experiments until there is at least a bit of comfort with the basics of the Stamp products. You will be amazed at your progress in a short time.

Then, you'll be able to ask and receive focused answers to your questions rather than a mad scramble to get unfamiliar equipment to work without damaging it (or yourselves).

Cheers,

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tom Sisk

http://www.siskconsult.com
·

stevertr

You're exactly correct, and we have no intention to do the thing ourselves here. The project we're working on has little to do with robotics, and so we were trying to not have to become "experts" to add this one component. Our hope was that if we ordered the correct materials, and had them in hand, I could then get physically go over to one of my friends who's adept in these things and have them help us put it all together and program it - as opposed to seeing him on the ball field and having him just etherally say "sure I can help." What I don't want to do is show up at his house with "x" and have him look at it and say, "well it's great that you have the board, chip and relays, but without the 'X' we really can't do anything with it.

Not sure if that made sense.

Quite honestly, as a person proficient in so many amazing things in my life, it's embarrassing that I've never been exposed to this stuff before. As such, I went out this week and ordered my 12 year old (my youngest unfortunately) a leggo robotics NXT kit, and I'm about to order a "How to program pbasic kit" for him to play with this summer. I want him to be one of those kids, like most folks here probably were, who truly know how to do this and carry it with them forever...

This is me by the way... http://www.stevelevine.com/magicmoments.htm

allanlane5

The BS2 "PBasic" language and IDE is quite a bit simpler, and more straightforward, than the NXT 'brick', so it shouldn't take too much.

The problem people have with relays is that the output pins of the BS2 can't source or sink enough current to drive a relay. The Darlington chip (ULN2803) CAN sink enough current to activate a relay, when driven by a signal from the BS2 that it should do so.

Having said all that, any platform you choose will have similar interfacing issues: how do you switch enough current to control the 'hot-wire', control the relays, implement the timing needed, read the altitude sensor, log the reading into an EEPROM. There isn't going to be any off-the-shelf solution for doing all this -- not a large enough mass-produced market for such a niche application. Having said that, the BS2 and Parallax makes the whole thing about as simple as it can get.

Steph Lindsay

Hi Stevertr,

Believe it or not, we have a free pdf book on this very subject called "Near Space" written by high-altitude balloon guru Paul Verhage. You can find a wealth of information, including chapter downloads, here:

http://www.parallax.com/tabid/567/Default.aspx

Also check out this high altitude photographic balloon project by Earl Foster:

http://www.parallax.com/tabid/565/Default.aspx

...and Payload-the Edge of Space·by Dave Harper:

http://www.parallax.com/tabid/569/Default.aspx

These are all posted to the Science section of our Customer Applications archives:

http://www.parallax.com/tabid/281/Default.aspx

Those interested in advanced scientific research balloons can read about Paul Voss' work here:

http://www.parallax.com/tabid/782/Default.aspx

This one is from the section of the same Customer Applications archive:

http://www.parallax.com/tabid/770/Default.aspx

I hope this helps!

-Stephanie

logan996

i would use the prop instead, use their dev board it is $30 and but the propeller idea book, they have some projects that show yyou sd card use and some good sensors, and how to use all differnt types of sensors, but first get the propeller education kit ($90)

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"WOAH! that wasn't supposed to happen!"