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  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-17 18:05
    Here (picture) is a straightforward way to connect that capacitor. One lead of the capacitor comes from pin 8 of the 3202 (the Vdd pin), and the other lead goes to a line in the protoboard immediately next to the 3202 (but not connected to any of its pins directly). Then a short piece of wire connects that line of protoboard holes to pin 1 of the 3202 (the Vss pin). (* But see below - I screwed up on that part. *)

    Post Edited (sylvie369) : 6/18/2010 4:32:17 AM GMT
    378 x 569 - 155K
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-17 18:59
    Sylvie,

    THANKS for the detailed explanation about which wires go where, and why. This will allow me time to decipher and digest·your post·so I can explain it to the Rocketeers in "kid speak" at Saturday's practice.

    OK, I plead ignorance on this: why·is it important that·the wire the capacitor runs through be as·short as possible? Does a longer wire "drain" capacitance? That is, will the capacitor not store as much power if the wire is longer? I continue to live and learn.

    Dry, red vino,·huh? Which do you prefer? I enjoy a·Chateauneuf, with medium rare steak of course, and a good mushroom sauce. Chateau Mont Redon '86 is excellent. Or Merlot, depending on the vintner. But enough of that; I'm getting hungry for steak (medium rare)!

    Thanks again for the excellent turorial! I'll get Christopher·busy (re)wiring the breadboard and adding the fourth wire tonight. Be sure to keep the launch rod vertical this weekend. We don't·want to·be·read·about 'Land Sharks in Wisconsin" (*unless they're from the late Paleozoic.)·I'm eager to hear·all about your flights.

    Best regards,

    Mark
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-17 19:13
    Mr.Kibler,

    What do you mean when you say the capacitor's leg?

    Sean
    Sean,

    ·This is a good question and I probably should have used a more technical term. But I'm not sure what·the "legs" are·called so I called them legs (they look like "legs"to me.) Andrew had it right when he said I was referring to one of the two wires·leading from·the capacitor (*nice diagram, with arrows for emphasis,·Andrew!) Maybe they're called "leads" but I'm not really sure. Maybe they're just called "short wire thingies" or maybe there's a real technical name we should learn.

    We learned from Dr. Allen and Sylvie that, if a capacitor (resistor, etc.) has one "leg" (lead?) shorter than the other, then one is positive and one is negative. That's called "polarized." It means that one side should have a postive charge going into it, and the other, a negative charge. Go back and re-read the post where they discuss it to learn more.

    Here'a homework question·for Sylvie and Dr. Allen: Do the two wires that come out of a capacitor, resistor, etc. have a technical name? Are they called legs, or leads, or... "short wire thingies"?·Do they have·a technical name we should know, learn, and use?

    Thanks Sean! Thanks Sylvie and Dr. Allen! Thanks Andrew (Team Graphic Designer)!
    Mr. Kibler
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-17 20:16
    Mark in NH said...

    Sylvie,

    THANKS for the detailed explanation about which wires go where, and why. This will allow me time to decipher and digest·your post·so I can explain it to the Rocketeers in "kid speak" at Saturday's practice.

    OK, I plead ignorance on this: why·is it important that·the wire the capacitor runs through be as·short as possible? Does a longer wire "drain" capacitance? That is, will the capacitor not store as much power if the wire is longer? I continue to live and learn.

    Dry, red vino,·huh? Which do you prefer? I enjoy a·Chateauneuf, with medium rare steak of course, and a good mushroom sauce. Chateau Mont Redon '86 is excellent. Or Merlot, depending on the vintner. But enough of that; I'm getting hungry for steak (medium rare)!

    Thanks again for the excellent turorial! I'll get Christopher·busy (re)wiring the breadboard and adding the fourth wire tonight. Be sure to keep the launch rod vertical this weekend. We don't·want to·be·read·about 'Land Sharks in Wisconsin" (*unless they're from the late Paleozoic.)·I'm eager to hear·all about your flights.

    I'm not the best source on that capacitor question, and it's entirely possible that yours is a situation in which it's not that vital. Again, I just stuck in a disc capacitor with 3/4" leads - that's right, they're called "leads" - and it seems to work fine. But in general, I believe the idea is that the capacitor is smoothing out the variations in voltage by acting as a sort of reservoir for electricity. If there are long connections from the reservoir to where the electricity is used, there are more opportunities for variations to build up again. Remember that your Vdd pin is also your voltage reference for the analog to digital conversion, so if it's going up and down wildly, so will your voltage readings, even if the voltage from the sensor is not changing.

    Re. the two different length leads: a device that has a positive and a negative lead is said to be "polarized". The capacitor you are using is not polarized. Generally those electrolytic capacitors (what you called "traditional") are polarized, and others are not (though there are exceptions). The polarity of an electrolytic capacitor is usually marked on the case, not by lead length.

    Chateauneuf, rare steak and mushroom sauce sounds perfect. Can you get that anywhere near Black Rock? If so, I'll make the trip. I'm mostly a Cabernet person. I have an outstanding bottle of very expensive Napa Valley Silver Oak Cabernet here, waiting for just the right evening.

    We haven't had any land sharks here that I can remember - we're more a lawn dart kind of group. I myself am more likely to have a perfect flight except the main snarls.



    My question for Dr. Allen: If Vdd is also Vref, they're going to be stuck with a 5V reference, right? What if the voltage range out of the sensor's test point doesn't get up nearly that high? Won't they wind up wasting most of the range of the 3202? I see it could be run from as little as 2.7V, so I'm wondering if you've been secretly considering having them add a voltage divider or something like that, to make better use of the 3202's range. Depending, of course, on what kinds of voltages come out of the CO2 sensor in the ranges of CO2 that they can expect in the flight.

    Post Edited (sylvie369) : 6/17/2010 8:24:45 PM GMT
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 00:45
    sylvie369 said...
    Here (picture) is a straightforward way to connect that capacitor. One lead of the capacitor comes from pin 8 of the 3202 (the Vdd pin), and the other lead goes to a line in the protoboard immediately next to the 3202 (but not connected to any of its pins directly). Then a short piece of wire connects that line of protoboard holes to pin 1 of the 3202 (the Vss pin).
    Sylvie,

    · I'm somewhat confused by·your picture of the AD converter on the breadboard. It would not be the first time today I have been confused. The·schematic that names the·AD pins indicates that the·"Din" pin is directly opposite (side-by-side) the "Vss" pin. The way I interpret the picture you posted, the short black jumper wire comes from the "Din" pin, connecting·the capacitor that goes to·the "Vss" pin. The "Vdd/Vref" pin that the capacitor and the "Vss" pin (are supposed to?) connect to is in the "opposite corner", diagonal from the "Vss" pin. Maybe I·just don't understand where the current flows on the underside of the breadboard, how one row and column connects to the other.

    They way I interpret the picture, current comes from (or goes to)·the "Vss" pin, then to the capacitor, out throught the capacitor,·then through the short black jumper wire, then (since it's in the same "row" as the black jumper wire) to the "Din" pin.

    I think (therefore I am... confused. Cogito ergo confuso.)

    Mark
    bmp
    94K
    AD.bmp 93.6K
  • Andrew (ARLISS)Andrew (ARLISS) Posts: 213
    edited 2010-06-18 01:04
    Mark in NH said...
    sylvie369 said...

    Here (picture) is a straightforward way to connect that capacitor. One lead of the capacitor comes from pin 8 of the 3202 (the Vdd pin), and the other lead goes to a line in the protoboard immediately next to the 3202 (but not connected to any of its pins directly). Then a short piece of wire connects that line of protoboard holes to pin 1 of the 3202 (the Vss pin).


    Sylvie,



    I'm somewhat confused by your picture of the AD converter on the breadboard. It would not be the first time today I have been confused. The schematic that names the AD pins indicates that the "Din" pin is directly opposite (side-by-side) the "Vss" pin. The way I interpret the picture you posted, the short black jumper wire comes from the "Din" pin, connecting the capacitor that goes to the "Vss" pin. The "Vdd/Vref" pin that the capacitor and the "Vss" pin (are supposed to?) connect to is in the "opposite corner", diagonal from the "Vss" pin. Maybe I just don't understand where the current flows on the underside of the breadboard, how one row and column connects to the other.



    They way I interpret the picture, current comes from (or goes to) the "Vss" pin, then to the capacitor, out throught the capacitor, then through the short black jumper wire, then (since it's in the same "row" as the black jumper wire) to the "Din" pin.



    I think (therefore I am... confused. Cogito ergo confuso.)



    Mark

    Mr. Kibler,

    I don't believe I can fully answer your question, but the schematic attached should help you better understand "where the current flows on the underside of the breadboard." As you can see, each horizontal row is connected, but not columns. Also note that the two groups of 5x17 holes are not connected in any way, rows or columns.

    Andrew
    391 x 449 - 40K
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 01:17
    Andrew,

    ·· Thanks for an excellent visual explanation·of the underside·of a breadboard. I understand it much better now. lol.gif

    Can we assume then, that the underside of all breadboards·are the same?

    So how do you interpret Sylvie's "blue breadboard" picture (see his post, above)? Is the "Vss" pin connected to the AD converter's "Vdd" pin through the·capacitor and the short black wire? Or is "Vss" connected to "Din"...?

    Please be sure to send an e-mail out to your team, reminding them that practice is Saturday, not Sunday. What is your plan for Saturday? What do you want to accomplish? Convey·it to your team ahead of time so they·will come prepared.

    Thanks,

    Mr. Kibler
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 01:38
    Sylvie and Dr. Allen,

    Attached is a diagram of how we understand the analog-to-digital converter to be wired. Are there any questions, comments, or corrections?

    The Rocketeers
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-18 04:28
    Mark in NH said...


    · I'm somewhat confused by·your picture of the AD converter on the breadboard. It would not be the first time today I have been confused. The·schematic that names the·AD pins indicates that the·"Din" pin is directly opposite (side-by-side) the "Vss" pin. The way I interpret the picture you posted, the short black jumper wire comes from the "Din" pin, connecting·the capacitor that goes to·the "Vss" pin. The "Vdd/Vref" pin that the capacitor and the "Vss" pin (are supposed to?) connect to is in the "opposite corner", diagonal from the "Vss" pin. Maybe I·just don't understand where the current flows on the underside of the breadboard, how one row and column connects to the other.

    They way I interpret the picture, current comes from (or goes to)·the "Vss" pin, then to the capacitor, out throught the capacitor,·then through the short black jumper wire, then (since it's in the same "row" as the black jumper wire) to the "Din" pin.

    I think (therefore I am... confused. Cogito ergo confuso.)

    Mark
    Shoot - my mistake. I convinced myself that pin 1 on the 3202 is Vss, but it's the chip select pin. That black wire should come from pin 4 (Vss) up to that row next to the 3202, not from pin 1. (* Corrected version attached *)

    I think, judging from what you wrote, that you're thinking I have the chip oriented the other way. In the photo, pin 1 (CS) is in row 27 on the bottom, Vss is in row 24, and Vdd is in row 27 on the top. The Din pin (5) is in row 24 on the top, and is not connected to anything. The only thing that should be changed from how I have it is for that black wire to go to row 24 at the bottom, not row 27.

    Can you see the little notch, and the dot on the chip in the photo, which indicate the orientation and pin 1? They're over on the left side of the chip.

    Rocketeers - the "adwiring.tif" graphic you sent looks correct to me. The only additional things you'll need will be the wire from the CO2 sensor to pin 2 of the chip, and the wires connecting the three grounds together.

    Post Edited (sylvie369) : 6/18/2010 12:01:04 PM GMT
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-18 04:32
    Mark in NH said...

    Can we assume then, that the underside of all breadboards·are the same?

    Every breadboard I've ever used had the rows connected the way they are in that diagram. They do differ in other ways, mostly in how the power and ground "rails" along the sides are connected.
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 13:20
    Sylvie,

    ·· The numbers for the AD pins in our diagram were wrong. The pins·were upside down in our diagram·(5, 6, 7, 8 instead of 8, 7, 6, 5.) So the black and white picture we posted above is wrong. We'll post a corrected diagram that shows where the wires go. Then we'll rewire the breadboard and post a picture of·it.

    I think we may be able to find a good steak house in Fernley, Nevada. That's where·we're staying during the ARLISS launch (check out Fernley Inn - Best Western.)·We have a female parent coming·along as one of the two requisite chaperones and I'm·the solo male chaperone. So there's plenty of room for you and Tracy to share my room... and breakfast is included each morning!

    We'll write more later after we re-do the wiring diagram and then rewire the breadboard.

    Thanks for the clarification,

    Mark
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-18 13:47
    Mark in NH said...
    Sylvie,

    ·· The numbers for the AD pins in our diagram were wrong. The pins·were upside down in our diagram·(5, 6, 7, 8 instead of 8, 7, 6, 5.) So the black and white picture we posted above is wrong. We'll post a corrected diagram that shows where the wires go. Then we'll rewire the breadboard and post a picture of·it.

    I think we may be able to find a good steak house in Fernley, Nevada. That's where·we're staying during the ARLISS launch (check out Fernley Inn - Best Western.)·We have a female parent coming·along as one of the two requisite chaperones and I'm·the solo male chaperone. So there's plenty of room for you and Tracy to share my room... and breakfast is included each morning!

    We'll write more later after we re-do the wiring diagram and then rewire the breadboard.

    Thanks for the clarification,

    Mark
    I see what you mean. You do have the right wires going to the right places, and the correct labels on each of the pins. However, your numbers on the right side are backwards, as you pointed out. Do not change where the wires go - they're already correct. Just redo the numbering.

    DIP ICs always have something to indicate where pin 1 is - either a little dot, or the indentation indicating the top side, with pin 1 being the upper left. Then you always count pins in a counterclockwise direction (rather than from top to bottom, then top to bottom on the other side, as your diagram has it).
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 14:47
    Sylvie,

    ·
    ··· Good morning. OK, let's try this. Attached is the revised wiring diagram with the AD pins numbers corrected and with your black jumper wire and capacitor added. I'll *try* to upload the picture Christopher just took of the newly wired breadboard. But with dial-up internet I may have to post it later today when I take him to work in Concord. He·was fortunate to·find a summer job where he patrols and maintains trails at the Forest Society.·We live out in the country and so I'll stop by Borders' for a cup 'a Joe... and some high-speed internet access.

    Questions:

    1) Should we add resistors to all the wires that go from the AD converter·to the BOE pins? One has a resistor already·but two don't.

    2)·Where do we·go with the programming? I'd like to have some of the Rocketeers wire more breadboards tomorrow at practice while others work on the program.

    Mark
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 15:09
    Sylvie and Tracy,

    Yes, we've been using the little half-moon shaped "dimple" as a reference point on the AD converter. I'm not sure how we got four of the numbers "backwards" but they're correct now.

    Success! The files uploaded (It took a kid to remind me that saving the picture·in "Paint"·would take less file space.) Duh! The picture isn't perfect resolution but it's very visible. The black-and-white diagram explains it well and I think we're all on the same page. What about adding resistors to the other two wires that go to the BOE?

    Theoretically·I have a very (very x 10 to some large exponent) basic idea where to be pick up with programming. The Rocketeers understand that:

    1) They have to decide which BOE pins the wires will go to, then define" them in the program. They want to share pins 12 and 13 with the LED, which Tracy explained will blink faster when the program is running. And we've grown fond of the LED's cheery "hello" blinking each time we run the program. It's sorta like ET's "heart-light". But I am aging myself by talking about the movie "ET".

    2) They have to·send program commands to the·AD converter from the BOE/ Stamp. Tracy started with some·16-bit s "DIR" program lines but I am lost here. Help!

    3) The program will include an algorithm(s) to convert mV to CO2 ppm. They (and I) are proud of the fact that they understand conceptually that the program changes mV into ppm by using math. They are also starting to·understand·how math and science are interrelated, and the relevance of math.

    Tracy, does the wiring look sound to you? Do have any observations or suggestions? Can you help us pick up where we left off with programming? Thanks!

    *I'm glad yesterday was the "last day of school...!" tongue.gif

    Mark and Chris

    PS - Sylvie, I got·the potentiometer you suggested at Radio Shack yesterday. I never realized there were so many choices.
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-18 15:36
    Mark, I don't think you're going to need resistors on any of the other connections. Tracy may correct me here, but I believe that the resistor is simply because you're sharing a pin as an input and an output, and it protects that BoE pin from being accidentally pulled in two directions at once. The other pins will be declared outputs (from the Stamp to the 3202), and there will be no danger of them being pulled high by the Stamp at the same time they're being pulled low by the 3202. I set mine up without any resistors at all, but using two different Stamp pins for Din and Dout: it works just fine that way.

    The DIR command tells the Stamp which pins to treat as inputs and which to treat as outputs. I'll let Tracy tell you the rest, rather than further confuse matters.

    Do you have a second BoE to hook up your 3202 breadboard to? I'd suggest, again, adding one of those potentiometers to provide a variable voltage source, connecting the +5V Vdd and the 0V gnd (Vss) to two of the potentiometer leads, and then connecting the other lead (the "wiper") from the pot to pin 2 (Ch 0) of your 3202. Then, again, connect all the grounds together, and run the 3202 sample program from the product page at Parallax.com. You should be able to see the pin reading and corresponding voltage on the lines representing channel 0, and see it change as you turn the pot's knob. Channel 1 will just jitter around randomly, because you don't have anything connected, though you could get it to read 0V or 5V by connecting it to Vss or Vdd.
  • Tracy AllenTracy Allen Posts: 6,658
    edited 2010-06-18 17:25
    Hi Rocketeers,

    I'm busy at work as this week comes to an end, so I haven't had time to keep up. (Okay, I also watched a couple of World Cup matches too!) I see you are figuring things out and that Sylvie is fielding questions and has an MCP3202 hooked up neatly on a breadboard. Take his advice about trying it out with a potentiometer as an input signal, apart from the ASP-2.

    Parallax provides programs, and Sylvie has a program working. Get those going. I'll be back in touch tomorrow, I hope in time for your meeting. Figuring things out for yourself is great exercise!

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Tracy Allen
    www.emesystems.com
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 21:09
    Tracy,

    · So who are you cheering for in the World Cup? How about that muffed goal in the US vs. Great Britain game? They don't get much easier than that...!

    Mark
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-18 21:14
    Here's where I'd shout "Allez les Bleues!", but there doesn't seem to be much point after yesterday. Sigh.

    My second choice is Spain, and they'll probably be out of it by the end of the first round too. I'm inclined to cheer for Chile after that.
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 21:33
    Sylvie,

    ·· "Les Bleues??" Ils sont d'ou? Canadien(ne)?" Allez Cote d'Ivoire!

    A tout a l'heure (or, as they say in les Etats-Unis, "toodle-oo")

    Marc
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 21:37
    Susanne (my wife) just commented, "Who played yesterday...? THAT's who "Les Bleues" are! So you see how much I know about hockey... (No, wait. That's the STANLEY Cup, isn't it...!) Tee hee lol.gif
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-18 22:05
    Ils sont d'ou? Zut!

    I watched the last World Cup final match, the one between France and Italy, with the (previous) French Ambassador to the U.S. and a couple of high-level Ministers. It was great fun until the tragic outcome was clear. There was much gnashing of teeth, but they didn't blame anyone, or commit suicide, or anything of that sort.
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-18 22:28
    Zut, alors!

    "Les Bleues", bien sur, sont les francais! Les italiens sont les "Vert and Rouge", je crois (peut etre?)·Vraiment, je ne sais pas. Je ne comprends pas l'hockey'. Pas du tout! Je parle "rocketese".

    Montgolfier
  • edited 2010-06-19 00:58
    Dr.Allen, Sylvie, and Mr.Kibler,

    Unfortunately, I haven't had a chance to watch any of the games but I heard the U.S lost/were down to Slovenia by 2. At least I think I am correct about that. Anybody else watch the Celtics game last night!?

    What is a potentiometer? Why do we need to have one and what exactly does it do?

    Sean
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-19 01:46
    Sean from ARLISS-NH said...
    Dr.Allen, Sylvie, and Mr.Kibler,

    Unfortunately, I haven't had a chance to watch any of the games but I heard the U.S lost/were down to Slovenia by 2. At least I think I am correct about that. Anybody else watch the Celtics game last night!?

    What is a potentiometer? Why do we need to have one and what exactly does it do?

    Sean
    The U.S. came back to tie Slovenia 2-2.

    A potentiometer is essentially a variable resistor. What you're going to use it for is to make a variable voltage that you can use to test your analog to digital converter setup. That 3202 chip reads a variable voltage from the CO2 sensor and sends out (to the BoE) a digital number from 0 to 4096 representing that voltage.

    Here's a pretty good look at some, and an explanation of how they work:
    http://en.wikipedia.org/wiki/Potentiometer

    You're going to connect 5V to one of the outer terminals, ground to the other outer one, and then the middle one will have a variable voltage on it, from 0v to 5v, depending on where the knob is turned. You'll attach that middle terminal (the "wiper") to one of the 3202's analog inputs (Ch 0 or Ch 1) to see if the 3202 is correctly reading the voltage on it. Here's where you can use that fancy voltmeter as well - you should be able to attach one lead to ground and the other to the wiper terminal of the potentiometer, and see the voltmeter read the same voltage that the BS2 program displays on the screen. It works just fine here on my setup.
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-19 02:45
    Sylvie,

    ·· I'm trying to visualize how the potentiometer is supposed to connect through the AD converter but I can't quite "see it." I'll need to get all the parts out again in the morning, before practice at 1 PM, and·re-read your descriptions. Then I'll put it together on the breadboard. Your potientiometer and AD conveter are mounted on a breadboard, yes...?

    It seems fairly straightforward; here's what I understand:

    1) The wires go from the (previously specified) potientiometer pins, to/ through·the specified AD converter pins, and into our spare BOE. The potientiometer and the AD chip are mounted on·our breadboard.

    "...connect 5V to one of the outer terminals, ground to the other outer one, and then the middle one will have a variable voltage... attach that middle terminal to one of the 3202's analog inputs (Ch 0 or Ch 1) to see if the 3202 is correctly reading the voltage on it."

    2)·Next we download and run the·3202 program from the Parallax website.

    3) As in voltage changes (or as we change the voltage on the potientiometer screw) we should see a corresponding change in 0 to 4096 on the computer screen.

    Why is the middle potientiometer pin called the "wiper?" Is it because·the pin·factors in to a voltage change (like a windshield wiper going back and forth...)?

    Tomorrow we have a lot to accomplish in·our few short hours together. Some of the new Rocketeers have rudimentary skills. I'll work with Andrew (Team Captain) and Dylan to get the potientiometer set-up working. I hope to have it·operational before they arrive for practice so I can guide them. Tracy wants us to help with the programming more and so I'll have Andrew do what he can after we have the potientiometer set-up working.

    Sean and Justin will be downloading and running·the program Tracy posted for the Team, the one·where you input·"any number" and it's multipled by 1.2207.·They need to leave tomorrow'spractice with a basic understanding (quasi-pun intended)·about where and how to put·a Parallax·program on the·computer/·screen. Did I·mention rudimentary? Christopher works from noon until 6 PM and·I'm not sure whether Mike will·be here.

    I think/ hope that the AD wiring is correct because I'd like to move through getting the potientiometer operational and into the programming the CO2 sensor. It seems like were close, yet far away... Our "team time together" is sooooooooooooooo limited and it gets tighter as we move into July. We'll hopefully meet again·sometime next week, but then·the Rocketeers·go·like seeds to the wind through July. We'll be lucky to meet just once during July and so I·really need to impress on the team the importance of·communicating through the forum.

    As you have seen, some are·very responsible about this but not all are.·My/our task is essentially·that of teaching half a dozen young teenagers the fundamentals of programming, from wherever we all happen to be, then asking them to figure out everything about the·BOE-MAWD-ASP-CO2 sensor in one fell swoop, with no background whatsoever... while they're on summer vacation! Sometimes I just scratch my head and giggle. In the final analysis some really good learning happens. But it is challenging sometimes, adn I appreciate your and Tracy's help more than you can ever imagine. I'm not a programming or electronics expert·by any means (not even close) but I do enjoy organizing and orchestrating projects for students who will benefit from them in both the short- and long term. So we move ahead.

    Hey, there's no "football" on TV! What time is it in South Africa anyway?!

    Je vais dormir. A demain, mon ami,

    Montgolfier
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-19 13:07
    Sylvie,

    OK, setting up the potientiometer was straightforward. I connected the:

    1) Potentiometer pin on one end to the BOE ----> Vss

    2) Potentiometer pin on the other end to BOE ----> Vdd

    3) Potientimeter "wiper" (middle) pin wired to AD converter pin channel 0.

    4) Downloaded and ran the sample program as suggested. These voltages appeared on the computer screen:

    ADC CH O: 4095
    ADC volts: 5.006
    ADC CH 1: 4095
    ADC volts: 5.006

    I understand that CH 1 voltage should not change because CH 1 is not connected to the potientiometer (though as you said, there may be some "flickering".)

    But when I adjust the small screw on the potientiometer to see a voltage change, CH 0 voltage does NOT change.

    I did not: "...connect all the grounds together..."

    QUESTION: Which "grounds get connected together" and where do they go once they're connected? The Vss pin on the AD converter to Vss on the BOE...?

    We will continue to experiment. Good luck with your launch today!

    Mark
  • sylvie369sylvie369 Posts: 1,622
    edited 2010-06-19 13:24
    Do you have a voltmeter available? You should make sure that the pot (potentiometer) is giving you the variable voltage you're after before you try to get the ADC to measure it.

    Set the voltmeter to measure voltage, attach the black lead to ground, and the red lead to the wiper pin on the pot. Then you should see the voltage change as you turn the knob.

    If that does not work, then you have a wiring problem in the connection of the pot. You might photograph the pot and let us see what you're working with.

    If you do get a variable voltage there but not on the computer screen, it's a problem with wiring the 3202.



    You wrote that you did not connect the grounds. The Vss pin of the 3202 must be·connected to the BoE's Vss, and that must be the same ground that you're using on the potentiometer (and eventually on the CO2 sensor).
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-19 13:27
    FLASH UPDATE: As we (Chris and I) adjust the potientiometer screw, the voltage and variable '4096' DO change. They flicker momentarily and we see a change flash on the screen. But the numbers reset back to 5.006 volts and '4096' almost instantaneously.

    QUESTION: Should the voltage change and variable stay on the screen when the the potientiometer screw is turned?? Or should it reset back to 5.006 volts and '4096' almost instantly? wHat do we do to keep the changes on the screen? I suspect it has something to do with the part where Sylvie said to "connect all the grounds together."

    We connected the AD converter's Vss pin to Vss on the BOE but that did not work.

    Mark and Chris
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-19 13:39
    We put a jumper wire from the AD converter's Vss pin to the wire that goes from one end of the potentiometer into the BOE's Vss slot.

    Chris is getting the voltmeter as I write. I'm uploading photo momentarily...

    Mark
  • Mark in NHMark in NH Posts: 447
    edited 2010-06-19 13:47
    Sylvie,

    Attached is the wiring photo. It seems clear enough if you enlarge it. The half-moon shaped AD "dimple is oriented to the left in the photo; Vss pin is the bottom right pin. We're getting the voltmeter out. You're up early out there in the Midwest (no doubt to watch "football'!)

    Mark
    1280 x 960 - 106K
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