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CRT monitor scavenging

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 25, 2011 1:47 pm

22 ohm - red red black

220 ohm - red red brown

:?

?

Also, do I have some leeway? can I use 33 ohm instead of 22 ohm?

edit: cool, found a calculator :) but my question still stands, do I need exactly 22 and 220 ohms or do I have some play?

Thewiki page seems to suggest so, and is also a bit contradictory regarding the smaller resistor. Help?
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Unread postAuthor: Hotwired » Tue Jan 25, 2011 2:04 pm

It's not a finely balanced thing, you can be a bit off.

I said earlier, it only needs one resistor, the small one is not essential.
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Unread postAuthor: jrrdw » Tue Jan 25, 2011 2:10 pm

My resistance values where approx 35ohms and 360ohms. Questions I'm pondering about my curcuit is did I have to much resistance? or was my transistor under specs for my use?

Wont under powering do damage as well?
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Unread postAuthor: Hotwired » Tue Jan 25, 2011 2:25 pm

I'm going to snip out the 220ohm from my old mini-flyback and try wiring up the CRT flyback with one resistor.

Now where's my bag of assorted transistors.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 25, 2011 2:38 pm

How does this look? I didn't get what terminals represent the "feedback coil" though, are they the black and red wires coming out of the flyback?
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Unread postAuthor: jrrdw » Tue Jan 25, 2011 2:51 pm

I think your question marks hook to each side of the primary coil. According to the schematic I used...
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 25, 2011 3:00 pm

I'm going with this schematic and figured out the pin identities using this advice, from what I can see in the schematic the primary coil hooks up as in my photo diagram, but I have no idea where on the flyback I would find the "feedback coil" outputs.
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Unread postAuthor: jrrdw » Tue Jan 25, 2011 3:09 pm

I have no idea where on the fly back I would find the "feedback coil" outputs.


Continuity tester. There are 3 different coils potted in that fly back.
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Unread postAuthor: Hotwired » Tue Jan 25, 2011 3:17 pm

Maybe 4 coils.

I've nuked one coil in my flyback by shorting a 12V lead acid battery through it (reads as dead now).

I've just got it working in flyback mode however using TWO resistors. These transformer types are not going to work with one.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 25, 2011 3:27 pm

OK, I think I have everything. Going to wire it up and see how it goes :D
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Unread postAuthor: Hotwired » Tue Jan 25, 2011 3:38 pm

I've got mine going again but it's a pain in the arse.

I've lost the high power resistors I originally used and I'm using a 1kohm variable resistor for the small 22ohm resistor. Only lasts for a short burst before I have to wiggle the adjusting screw


Nevermind. Just found them, box was hiding at the bottom of another box :?

With the lego brick sized 3 watt wirewound resistors - still 220 and 22 ohms it puts off a nice arc from a 12V lead acid.

Again with the dodgy camerawork with the keychain camera but I think I'm getting better at aiming it:

[youtube]http://www.youtube.com/watch?v=cDiLA-1R-JE[/youtube]
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 25, 2011 4:51 pm

haha win!

[youtube]http://www.youtube.com/watch?v=q0278HEVGmQ[/youtube]

Doesn't seem as powerful as Hotwired's (I'm using a 12v 1 amp supply), but looks good enough :) bit late for testing a high mix hybrid but I gave the tennis ball launcher a whirl and it worked beautifully.

Thanks to everyone who put up with my cluelessness :oops:

Here's the setup, twisted wires all the way :roll:
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Unread postAuthor: Hotwired » Tue Jan 25, 2011 4:56 pm

Terminal view of my flyback:

Image

Each circled group is of terminals on the same coil, found using a continuity tester.

The pin on its own is the return for the high voltage.

The bottom group was burnt out with excessive current so I'm now using the two furthest right from the group at the top for the primary coil.

For the feedback coil I used the bottom two pins from the group of four.

The polarity of the coils helps, switch the connections round on the primary and the flyback one pair at a time.

Transistor I found working best for me was a BUX127 rated for 50V, 15A, 125W. Still needs a heatsink for longer use.


Ahar yours is working. Great stuff.

And a reminder for me as to why I bought a large pack of crocodile clip test leads :)

The type of transistor as well as the power supply affects the arc a lot, I've got similar rated transistors which are abysmal in this circuit.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 25, 2011 6:21 pm

Hotwired wrote:Ahar yours is working. Great stuff.


Thanks for the help :)

Hotwired wrote:And a reminder for me as to why I bought a large pack of crocodile clip test leads


Yep :roll:

Now that I have it working, I'll probably use JSR soldering (dab of araldite over twisted wires :D) to put it together more permanently, then put it in a container with a 12V CPU fan to keep things cool.

In the meantime, here it is in action as the ignition for the clear tennis ball combustion, *whooph* :D

[youtube]http://www.youtube.com/watch?v=gsMf-sDDCMQ[/youtube]
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Unread postAuthor: Fnord » Tue Jan 25, 2011 7:17 pm

Holy crap JSR you actually got a flyback working on your first try? That is indeed a win.

Be careful with the input voltage. My first try worked fine with 9 volts but fried quickly with 12.

Here's a beefed up version that may help out if your current setup proves ineffective. You can probably fine the 25v capacitor in your junk somewhere. Exact valves aren't critical. The diode should be an ultra-fast recovery type and the 200v capacitor should be a high-quailty foil-film cap(they usually look like plastic boxes).

You may want to buy some transistors eventually, in this case I found a 2n3773 works well.


This circuit upped the voltage of my charger slightly, but kicked out roughly 5 times the current.


edit: here's a nice flyback powered by a MOT :)
[youtube]http://www.youtube.com/watch?v=655uZTywQ5I&feature=related[/youtube]
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