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ignition coil question

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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ignition coil question

Unread postAuthor: singularity » Tue May 08, 2007 9:31 pm

alright as of right now i have a 3 to 12 kHz ne555 pulse generator, and ignition coil and a temporary power source. what i need is the cable to connect to the 50kv output and i need to know where i should ground it too? also what type of batteries should i use to power this thing i want to be portable but its going to be mounted an average size combustion. i was think like 3 6 volt cells in series, or is that overkill?

hers some pics

heres the pulse generator, the batteries are just kinda thrown in there if they were connect it would turn on (theres no switch rite now)

<img src="http://i78.photobucket.com/albums/j85/irwinner_2006/DSCN2386.jpg">

hers the hole thing

<img src="http://i78.photobucket.com/albums/j85/irwinner_2006/DSCN2387.jpg">

heres another view

<img src="http://i78.photobucket.com/albums/j85/irwinner_2006/DSCN2388.jpg">
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Unread postAuthor: frankrede » Tue May 08, 2007 10:12 pm

How about a RC car battery?
I'm sorry, I have little experience in the electronics realm.
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Unread postAuthor: ammosmoke » Wed May 09, 2007 1:01 am

Uh, remind me, what does a pulse generator do?
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Unread postAuthor: jimmy101 » Wed May 09, 2007 9:02 am

... what i need is the cable to connect to the 50kv output and i need to know where i should ground it too?


Any old wire can be used as the cable for the HV (but automotive spark wire is not a good idea since it is very high resistance).

The Gauge of the wire doesn't matter at all.

You would like wire with a high voltage insulation but that can be hard to find. Most people use more or less generic, single conductor insulated wire. If you keep the wires well separated then they won't arc through the insulation. As a rough rule of thumb, the wires should never been any closer than the width of the spark gap. Old style TV antenna downlead wire, the flat kind that has the two insulators separated by ~1/4" might work if you want to use two conductor wire.


Automotive coils are autotransformers which means the primary windings and the secondary windings share one connection. If you have an ohm meter you can measure the resistance between the secondary (high voltage) output and the two low voltage primary terminals (usually marked as "+" and "-"). The terminal you want to use as the ground is the one that has the highest resistance to the HV terminal. (IIRC the primary will actually spark to either of the low voltage terminals. One of the primary's connections is at 0V, the other at 12V, compared to tens of KV on the secondary 0V=12V.)

EDIT: Another way to do it is to just stick a wire in the HV and bend it over near the + or - terminals and see if it sparks. I believe you can get sparks to both the + and -.
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Unread postAuthor: spudzinger » Wed May 09, 2007 5:46 pm

A golf cart battery might work. What are the ICs (other that the 555 timer), you should draw up a schematic and a parts list. On the question of grounding, wont one of the leads coming off the coil ground it? Oh, and why is there a USPS sticker on your breadboard, lol. Please, at least, PM me with a parts list, looks fun.(I am a robotics/electronics geek)Good luck Spud
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Unread postAuthor: jimmy101 » Thu May 10, 2007 11:50 am

The RC car battery is a pretty good idea, it should have high enough voltage and a fair amount of power. And, if you have the battery then you probably have the correct charger for it.

Car batteries, motorcycle batteries, or any 12V lead acid battery would also work but they a pretty big and heavy (and expensive).

All Electronics has some pretty good small sealed lead acid rechargeable batteries with a fair amount of "oomf" in'm;
12 VOLT 1.4 AH LEAD-ACID BATTERY ASSEMBLY for $9.50 (3.95" x 1.98" x 2.50")

Two 9V batteries in series will also work but you'll use the batteries up pretty quickly. (I don't recall the maximum voltage rating of a 555, will it take 18V?)

If you don't need portability a 9~15V wall wart would work. So would an automotive battery charger.

(BTW, be careful with car batteries and charges, there is enough amperage there to knock you on your ass.)

Ammosmoke: The pulse generator just switches the power to the coil on and off at a fairly high rate. The 555 timer chip gives a nice square wave shape which works very well with the ignition coil. The coil gives a high voltage output spike every time the input voltage is turned on or off.
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Unread postAuthor: singularity » Thu May 10, 2007 7:53 pm

parts

LM7812
2 diodes (generic got them from r/c car circuit)
5k variable resistor
25k variable resistor
100 ohm resistor
1k resistor
.1uf cap
.01uf cap
470uf cap (filter cap any value above 100 should be fine)
ne555
engine coil
2n3055


here is the diagram i used, i modified it a bit so i didn't need to actually buy any pieces, switched the 100k resistor for a 25k, put a 12v regulator in the place of the 5v one, changed the filter cap value.

<img src="http://i78.photobucket.com/albums/j85/irwinner_2006/cad-coil-crct.jpg">

the 2n3055 isn't in the picture wired it in later and the led is just so i could test the frequency. as for the postage sticker its actually tape very similar to packing tape except it looks less professional (yay for ghettoing but seriously this is the best tape i ever used, i don't think you can get it any more) all the pieces i used came form crap i had lying around (dead rc cars, old psu's, dead motherboards, ect) so feel free to modify. the only thing i bought was the engine coil, im thinking im going to use some old 9.6v Ni-MH batteries i found just have to make sure i have the charger. im a little hesitant on using a common ground had a bad experience with a coil gun and a common ground (actually 3 bad experience before i figured it out).

* note to reduce current consumption add resistor to coil but make sure it can handle the heat and amperage
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be sure to check out my <a href="http://www.spudfiles.com/forums/ak-style-airsoft-vortex-gun-t10959.html">AK Styled Vortex Gun</a> and my <a href="http://www.spudfiles.com/forums/at-4-t9627.html">AT-4 Rocket</a>

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Unread postAuthor: spudzinger » Fri May 11, 2007 5:06 pm

thanks for putting up the info, and a great schematic (I have seen some very bad ones)About how much did the coi; cost and where did you get it (Autozone,junkyard,napa,etc?)Thanks
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Unread postAuthor: singularity » Fri May 11, 2007 5:19 pm

i rode my bike to NAPA ad bought the thing for $23, its a "universal ignition coil". i was intending to buy <a href="http://www.napaonline.com/MasterPages/NOLMaster.aspx?PageId=470&LineCode=BK&PartNumber=7355273&Description=Ignition+Coil+-+Accel"> this one</a> but they were out of stock. it will generate a better spark and its only $10 more you probably don't need it though. you could go to the junk yard but these things die over time so it doesn't mean you get a good or even an operational one.
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be sure to check out my <a href="http://www.spudfiles.com/forums/ak-style-airsoft-vortex-gun-t10959.html">AK Styled Vortex Gun</a> and my <a href="http://www.spudfiles.com/forums/at-4-t9627.html">AT-4 Rocket</a>

upcoming projects... finalized clip fed BBMG and ball point pen sniper
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Unread postAuthor: spudzinger » Fri May 11, 2007 5:42 pm

sweet, well i can get one from my dads many dead Saabs or maybe from my Bronco II or one of my uncles dead motorcycles (for lighter duty?)
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