Help with student project idea

Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
Hi all. Sorry I've been gone so long. It's been crazy busy around here. Anywho, on to my topic. We're working a science fair of sorts for the students around here as part of a project to get kids to think outside the box. (you'd be surprised how hard that is these days) The idea I have for my piece of the project is to build a pedal powered generator using off the shelf and readily available parts. IE, old stuff/parts you'd find laying around the house. Now, onward to my question. The 12v AGM batteries I'm using have a 2amp (28w) maximum safe charging rate. Since I'll have no charge controller on my setup (unless you guys know how to build a mechanical one, I'll have to forgo having it per the rules of the project), I'm looking to keep the motor output at 28w or less. The question is, what 12vdc motor would give me that?

Would I be safe using the blower fan motor from a car (ie, the one used for the heater), or should I look for something else? The idea here is that you're supposed to use only spare/scrap/off the shelf stuff that any kid can find in their home, and the project budget must be $20 or less. I'm going to use my $20 to pick up a 36 count pack of 10amp 1000v blocking diodes (I don't want to run this project without them if possible). But the rest I want to get off the shelf. My setup also has to be entirely mechanical and can't have any electronic parts. The diode I think would be allowable, as it's not technically an "electronic part". Even if it was, I plan to use it anyways because I'm not about to attempt this without one. Too much bloody work. Anyhow, that's my question. On a side note though, the bike powered battery charger project would be a cool way to convince kids to exercise more. But that's another story. ;)

Comments

  • westbranchwestbranch Solar Expert Posts: 5,142 ✭✭✭✭
    Re: Help with student project idea

    Dumb question maybe, but just what is it you want them to learn 'outside the box'?
    maybe they need to learn how not to destroy a battery by actually destroying :cry: one?....

    an old saying is that you never learn anything by not making a mistake, otherwise life is boring...

    hth
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Help with student project idea

    unfortunately, a diode is an electronic part. now this part may be found laying around in my house, but my house is not the typical household. now without finding the right motor one may possibly use spinning magnets through a fixed coil (or several), but it could also be argued that the magnets and wire is not always something laying about in a typical household either.

    it may be better to do an air solar thermal collector with glass, wood, and insulation. the insulation can be several layers of cardboard and these are common things unlike diodes. the inside should be painted black, but if it's argued that black spray paint is not common enough then use charcoal to darken the inside.
  • fix_it_guyfix_it_guy Solar Expert Posts: 26
    Re: Help with student project idea
    niel wrote: »
    unfortunately, a diode is an electronic part. now this part may be found laying around in my house, but my house is not the typical household. now without finding the right motor one may possibly use spinning magnets through a fixed coil (or several), but it could also be argued that the magnets and wire is not always something laying about in a typical household either.

    it may be better to do an air solar thermal collector with glass, wood, and insulation. the insulation can be several layers of cardboard and these are common things unlike diodes. the inside should be painted black, but if it's argued that black spray paint is not common enough then use charcoal to darken the inside.

    Black construction paper would work to. Niel it sounds like your home is similar to mine, you never know what you'll find just laying around. That is in my shop anyways, I have children and a lot of what you might find isn't exactly safe for kids.
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Help with student project idea

    you're right as many places have some of it on hand from leftover projects, especially roofs.
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    Westbranch, the idea here is to get kids looking at the things around them differently than they've been raised to do. Such as finding ways to re-purpose everyday objects into usable items. Some examples the others are doing is a plant drip watering system (for hanging or potted plants) made out of a 2 litter bottle, some fish tank hose, and some other things to regulate the flow and drip rates. Basically we're looking to get kids looking for solutions that come from their immediate environment and don't require them to drive down to the local Walmart or online at Amazon to solve issues. One of the adult leaders called it the "after school epic kludge science festival." :)

    Neil, those solar thermal collectors might be an idea we could build at the next festival in a few months. I'm already looking into building a Sterling engine (if I can find a viable set of blueprints or instructions on how to do it) out of scrap parts if possible for our next festival, but that solar thermal idea might be a good alternative if I can't. If I can, I could probably combine the two somehow. But I first have to get through this one. lol.

    To give you guys a little background on this project, it's an idea forwarded by one of the old timers around here. He complained to the other parents about how nobody knows how to fix anything anymore, or make use of their environment. IE, everyone is stuck in a one use and throw away mindset. They're all used to getting their solutions ready made from the store, and if something is no longer needed it's just pitched rather than re-purposed. Coming from a farm I know exactly what he's talking about as we did that a lot too, putting every ounce of cast offs and trash to use in one way or another, never wasting anything. So after some brain crunching we decided to do a sort of science fair that showed kids how to recycle things or find solutions in their immediate environment through simple "outside the box" thinking. We plan to do several of these this year and the local schools love the idea. On top of that, for natural born kludgers like myself, it's a fun outlet for what's presently a practical hobby. :)
  • PhotowhitPhotowhit Solar Expert Posts: 4,996 ✭✭✭✭
    Re: Help with student project idea

    If you haven't done the paperclip motor it is very simple and teaches a good bit. every thing can be had in a typical house. No need for "Magnetic wire" if someone uses finger nail polish! strip some solid wire (thin like phone hard wire' and apply and strip the ends, Don't really need a ceramic magnet, but the stronger field makes things work easier. don't 'need' 9v battery, but any battery....
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • fix_it_guyfix_it_guy Solar Expert Posts: 26
    Re: Help with student project idea

    Oh man... I'm the repurpose champ, I should be the keynote speaker at your event. LoL My shop is full of all kinds of interesting things. Actualy just today I was creating these Solar Window Heaters out of plastic water bottles, hollow square plastic stock, and a metal rod from a baby playpen. I should start a thread about them and post some pics. I want you guy's opinions.
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    Well, if Neil has no issues, I say go for it. :D Also, this is our first time doing this, so we're gonna see how it goes, and if it flies really well with the kids, we might just invite you down. :)

    Also, I passed along the ideas from the rest of you to the others and a couple are gonna snag the ideas and run with them. I'm still trying to get the bike generator idea running first to see if it'll work because I have an ulterior motive for my design. (ie, getting kids to exercise by making it fun. :D) But if it doesn't work I've got some other ideas on the cooker. One of them is building a cardboard and tinfoil solar cooker. :D
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Help with student project idea

    no objections here and it sounds like it may be interesting and even enlightening for some readers that are out there.

    i have found that the current generations are pretty useless in some ways. when you take your car in to be serviced if the computer or idiot light doesn't say something to today's mechanics, they are often lost as to what a problem might be and many don't acknowledge there is a problem if neither says so.

    case in point. my brother and sister in law are having trouble with their jeep rear wheels screeching when in motion and the brakes aren't even applied. the brakes themselves are fine. i'd know of a few other things to check and i'm not a mechanic. they didn't have a clue and sent them on their way saying nothing is wrong.
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    Wow, if it's not the brakes I'd be checking the wheel bearings really bloody quick like. Losing a wheel at 70mph sucks beyond words.

    As for the kids being useless, they really are. We call them to pre-undead, and the "living zombies". Case in point. Local guy had a chainsaw that wouldn't start and nobody could figure out why. One rebuild kit, an hour soak of the carburetor in gas and a can of compressed air and it ran like a charm. :)
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    Well, I found a solution to my charge controller issue. Instead of either chancing it or going with an electronic charge controller, I made my own. It's kinda interesting too. All it consists of is a 12vdc magnetic actuator, a spring, and a toggle switch. The way it works is simple. As the voltage increases, so does the power of the magnet, and the more it pulls on the spring. Of course at the connection between the spring and the actuator is the toggle handle for the switch. The more amps goes through the magnetic actuator, the more it pulls on the spring and the more it turns down the slide switch which in turn decreases the amps flowing through the circuit. It's still able to go above 2 amps but you about have to throw the motor apart to do it. At standard operating speed it allow through about 1.75amps on average. It took me a while to tune the sucker (ie, playing with spring strengths mostly), but once I got it right, it works like a dream. :)
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Help with student project idea

    Congratulations! You've just re-invented the mechanical Voltage "regulator" (cut-off) used on vehicles for decades. :D
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    lol. Yeah, I probably have. Although voltage regulators in cars haven't been mechanical since the 80's. So I couldn't steal one of those. :(
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    Hey guys, what's a good blocking diode for a 12v system up to about 10amps input? I haven't found anything specifically 12v 10amp, but I have found a 50v 25a unit, and a 50v 6a unit. At this point I don't care if the unit is too big, but I am afraid of it being too small, because I'd rather have too much capacity than not enough. Exploding diodes are a bad thing. So is magic smoke. ^_^;;
  • BB.BB. Super Moderators, Administrators Posts: 29,518 admin
    Re: Help with student project idea

    You probably want at least a 25 volt diode (to allow for playing around--Possibly even a rectifier or diode shunt on the generator in case people start peddling backwards (otherwise you could be looking at a blocking diode capable of 12 volt battery + 50-100 volts og reverse voltage from back pedaling--if the gearing allows).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    http://www.arrownac.com/parts/detail/2925830S7858708N2867

    So one of these bad boys then?
  • BB.BB. Super Moderators, Administrators Posts: 29,518 admin
    Re: Help with student project idea

    Should work, you may have to put on an insulated heat sink.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Solar Expert Posts: 10,311 ✭✭✭✭
    Re: Help with student project idea

    that is a bridge rectifier and as such it has 4 diodes in it. you are only using one of them so it's kind of a waste.

    try this as there's lots to pick from,
    http://www.mouser.com/Semiconductors/Discrete-Semiconductors/Schottky-Diodes-Rectifiers/_/N-6hpdn?P=1z0waptZ1z0y4ci

    you can filter it further like for a high reverse voltage or better forward voltage drop. (lower is better for v drop)
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    Thanks Niel! :D
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    Well, we did the prelim demonstration tonight for the school teachers and staff (the actual show isn't until Saturday) and it went over huge!!! They're really excited about this, and from the feedback we got from them and the couple PTO members who showed up, it should go over huge. My bike generator display was a huge hit as well. One of the teachers even made a joke about building one and tying it to her son's PS3 to encourage him to exercise. IE, no pedal, no games. lol
  • BB.BB. Super Moderators, Administrators Posts: 29,518 admin
    Re: Help with student project idea

    Attachment not found.
    pics? pics?
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Steven LakeSteven Lake Solar Expert Posts: 395 ✭✭
    Re: Help with student project idea

    Sorry, I forgot to bring my camera. I had a hard enough time remembering to bring all my parts. :( I ended up making two trips home because I forgot stuff. Argh. I'll try to get you some this weekend.
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