Author Topic: Ignition for dummies (me)  (Read 5639 times)

Offline PJW

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Ignition for dummies (me)
« on: April 09, 2014, 03:38:35 PM »
I am well on the way to finishing a webster IC engine, i have some 6v ignition bits but I am not sure how to wire them up or if they will do the job, I am sure some of you will be kind enough to point me in the right direction. I have got two pics, the first I could follow, just & the second is the coil I have, it only has one spade connection and the HT lead :zap: also I dont have a condenser yet and where will that fit in the system. :slap:
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Offline PJW

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Re: Ignition for dummies (me)
« Reply #1 on: April 09, 2014, 03:45:51 PM »
+This is where I am with the build, I have the fuel tank to fit & may have to re visit the valves!
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Offline philjoe5

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Re: Ignition for dummies (me)
« Reply #2 on: April 09, 2014, 04:33:09 PM »
Hi PJW,
I just went through this so now I'm an expert (dummie :zap:)

Here's the circuit diagram


and here's a picture


the blue wire on the right is the ungrounded lead from the points, the red wire is from the condensor to a common where the wire from the (-) side of the coil is also attached.  That's the 3 wire junction shown in the diagram above the condensor.

Your engine looks grand BTW

Cheers,
Phil
If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man.  - Mark Twain

Offline PJW

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Re: Ignition for dummies (me)
« Reply #3 on: April 09, 2014, 09:11:04 PM »
Hi Phil, the coil I have has only one terminal, that is my stumbling block. I have a 6v power supply & this 6v coil, I was hoping that I could use these, i know I need a condenser but it would be an inexpensive and a nice small solution.
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Offline cheepo45

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Re: Ignition for dummies (me)
« Reply #4 on: April 09, 2014, 09:15:24 PM »
I have been using this setup on my Upshur engine for years. It has been very reliable. You will need to change the points occasionally if you run it a lot.
           cheepo45
                 

Offline PJW

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Re: Ignition for dummies (me)
« Reply #5 on: April 09, 2014, 09:58:25 PM »
It looks like this coil is not suitable then?
by the way Phil, your engine looks interesting, water cooled? looking good :praise2:
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Offline Baron

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Re: Ignition for dummies (me)
« Reply #6 on: April 09, 2014, 09:59:54 PM »
Hi Phil, the coil I have has only one terminal, that is my stumbling block. I have a 6v power supply & this 6v coil, I was hoping that I could use these, i know I need a condenser but it would be an inexpensive and a nice small solution.

The metal body of the coil is usually one of the connections on that type.  It would be bolted to the chassis and grounded to one side of the battery.

Almost any 0.1 to 0.5 microfarad capacitor will do.
« Last Edit: April 09, 2014, 10:03:40 PM by Baron »
Best Regards:  Baron.

I donít regret the things Iíve done, I regret the things I didnít do when I had the chance.

Offline PStechPaul

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Re: Ignition for dummies (me)
« Reply #7 on: April 09, 2014, 10:57:14 PM »
It looks like your coil has only the one slip-on connector, plus the high voltage lead, and the metal body which would probably be grounded. But that means that the points would have to break the voltage from the battery, and that won't work because the points are usually grounded (as well as the condenser). So you may need to insulate the metal frame of the coil and connect it to the battery (through a fuse, of course), and then the connector could go to the points which would energize the coil when closed, and cause a spark when they open.
 
I am going to build an electronic ignition something like this:

 
The transistors greatly reduce the current and voltage on the points, and also should make the timing much more accurate as well as increase the intensity of the spark. Any sparking on the points is energy that is not going to the spark plug, and the timing of the highest voltage of the ignition spark will be delayed until the points open sufficiently. I think this is why Brian's double opposed piston engine did not run well at low speeds, and required a very high degree of advance BTDC.
 
If you build the circuit above, you must use a high voltage rated power transistor and not the 2N5550 as shown. I bought some of these:
http://www.mouser.com/Search/Refine.aspx?Keyword=771-BUJ403
http://www.mouser.com/ds/2/302/BUJ403A-101963.pdf

Offline PJW

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Re: Ignition for dummies (me)
« Reply #8 on: April 10, 2014, 07:25:06 PM »
thanks for all the replies, Paul your diagram went totally over my head, I will start playing now & see what happens :zap: :zap: :zap: :whoohoo:
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Offline Camm-1

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Re: Ignition for dummies (me)
« Reply #9 on: April 10, 2014, 08:43:42 PM »
I buy these cdi ignitions, cheap and easy to conect and dont take much place.
http://www.hobbyking.com/hobbyking/store/__10996__Replacement_CDI_Ignition_for_RCG_50CC_Engines.html

Offline Zephyrin

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Re: Ignition for dummies (me)
« Reply #10 on: April 10, 2014, 10:08:34 PM »

You have to test your coil with an ohmeter to find the terminals of the HT and LT coil, very easy.  most probably the internal connection between the 2 coils is also connected to the body. so the secondary coil is between body and HT lead, and the primary coil between body and +, and has the lowest resitance.
then you connect your coil and battery according to the diagram, and not connecting the body of the coil to the earth, but to the isolated point of the contact breaker. and a capacity too, 0.2 microfarad 250V between the 2 points. You will see easily if you get a spark on running the engine by hand. funny to test, nothing wrong to try.


Points and contact-breaker work pretty well. I use this setup on my engines, the coil is a "modelelectric" one, very small and smart, or one from a moped, (the old model with HT & LT coils both in a single unit, new copies available on EBAY. A ordinary 4.5 V battery gives sparks with a rimfire 1/4 sparkplug and also with a CM6 NGK.

Online Jo

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Re: Ignition for dummies (me)
« Reply #11 on: April 11, 2014, 07:18:40 AM »
I buy these cdi ignitions, cheap and easy to conect and dont take much place.
http://www.hobbyking.com/hobbyking/store/__10996__Replacement_CDI_Ignition_for_RCG_50CC_Engines.html

I originally ordered one of those for my R&B. It was on "Back Order".. after 3 months of it not turning up I gave up and brought a different CDI ignition from just Engines which I could never get to cause the engine to bang :ShakeHead:

Jo
Usus est optimum magister

Offline PJW

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Re: Ignition for dummies (me)
« Reply #12 on: April 11, 2014, 07:07:15 PM »
Hi Zephyrin, I ran the ohmeter over the terminals, I got continuation between the spade connector & the frame and a slight movement between the HT lead & spade connector.
Will I be right with live to spade connector, wire from frame split to points & condensor then both to earth, not forgetting to isolate the frame!
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Offline Baron

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Re: Ignition for dummies (me)
« Reply #13 on: April 11, 2014, 08:19:07 PM »
Hi Zephyrin, I ran the ohmeter over the terminals, I got continuation between the spade connector & the frame and a slight movement between the HT lead & spade connector.
Will I be right with live to spade connector, wire from frame split to points & condensor then both to earth, not forgetting to isolate the frame!

That sounds fine.  The thing is just a transformer with two windings !
What ever gear that ignition coil was originally on probably had the contact breaker in line with the tag.
Look up "Kettering Ignition" on Wikipedia.

Best Regards:  Baron.

I donít regret the things Iíve done, I regret the things I didnít do when I had the chance.

Offline PJW

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Re: Ignition for dummies (me)
« Reply #14 on: April 11, 2014, 09:43:19 PM »
thanks for that, the coil was off (no for) a Vespa. Looking for a condensor but they dont mention the mf value just state what car it will fit, they all seem different and with my using a 6v power & coil it is making me scratch my head a bit :shrug:
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Offline PStechPaul

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Re: Ignition for dummies (me)
« Reply #15 on: April 12, 2014, 07:29:01 AM »
Probably anything from 0.1 to 0.5 uF, and 400V or more, will be fine. The capacitor (condenser) forms a tuned resonant circuit with the inductance of the coil primary and this provides a damped oscillation that can extend the time of the spark. A larger capacitor will give less voltage but longer time.

Offline PJW

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Re: Ignition for dummies (me)
« Reply #16 on: April 12, 2014, 10:43:29 AM »
thanks for the info, I have found a capacitor locally  so I can have a go soon :pinkelephant: :whoohoo:
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