Ignition Amplifier Kit

[Barry]

There has been lots of discussion about the various electronic ignition systems available but I don't recall anyone doing it the cheapskate way and building one from a kit.  So...  I've had this Velleman K2543 Transistor Ignition kit on the shelf for some time originally intended for a car I think.

This is a very simple device with 2 transistors 6 diodes 7 resistors and 1 capacitor. I built the unit up on the provided circuit board and fitted it into a very compact case substituting the supplied heat sink with a neat aluminium lid. The unit is connected with 4 wires retaining the points and advance mechanism so it is very simple to revert to standard in the event of failure.

As a comparative test I opened up a set of old plugs to .100" and laid them on top of the barrels. Cranking the engine over with the standard setup produced  a spark more orange than blue.  With the amplifier in circuit the spark was bluer if not noticeably stronger. At least it worked !

The theory of an ignition amplifier is it switches the coils faster which should produce a stronger spark particularly at low revs and the other benefit is the points last much longer.

Early days yet but the bike started instantly and seemed to run cleaner and stronger at low revs all subjective I Know.

Anyone else used one of these kits ?  They are still available for approx. £10 just Google Velleman K2543.

[Bob_Roller]

How does the unit look as far as water resistance, is it a sealed unit ?

[nhmaf]

I had the same question about moisture resistance too.  Longevity-wise, its reliability is also dependent on the end-user's soldering skills, so some people may do well while others will not due to poor soldering.
If the transistors are not surface mount are they bolted on?  vibration can be very bad for solder joints too if the body of the transistor isn't either bolted down, or affixed with some RTV  to quell mechanical bending of the leads.

[Barry]

Well I wouldn't describe it as totally water tight. It's just a slim plastic box I happened to have. To be honest the hardest thing about this kit is finding a suitable box to put it in. Hopefully it's out of the worst of the weather up there under the tank. I also chose that location to keep the leads  as short as possible. The circuit board and power transistor are bolted solidly to the aluminium cover/Heatsink.  I've been soldering professionally for 35+ years so hopefully I did a good job. An good option would be to "pot" the whole thing in epoxy resin. That would resolve all concerns about vibration and water. Rubber mounting it would also be very easy to do. I want to make sure it works well first. Did 70 miles on it today and everything was fine.  I do like this instant starting from cold the engine hardly seems to turn over before it fires.  

[nhmaf]

It looks like you've done a good job of mounting it in a good spot - I hope that it continues to work well for ya!  If you seal up the joints and screw holes into the box with silicone sealant that would probably do well enough for water-proofness in that location, I think.

What coil(s) are you using?

[Barry]

I’m using the standard 1.5 ohm coils so I might be able to upgrade to a pair of the later 0.7 ohm coils or 1.5 ohm dual output coil.  It depends on how much current this ignition amplifier can handle.  It’s rated nominally at 4 Amps which would seem to rule this out  but you can’t do a simple Ohms law calculation in the dynamic situation where coil impedance will reduce the average current drawn. I would have to take some measurements first and even then I will be on my own if I exceed the makers specifications. Subjectively the ignition Amplifier is running surprisingly cool so there may be some scope.  

[nhmaf]

I don't have a PSpice model for the ignition coil, and I'm having trouble getting an accurate model for the venerable (old) TIP162 - which is actually a Darlington NPN (but they show it as a regular BJT in their schematic).  If I do work these out, I Can give you more info, but the TIP162 can take sustained 7A provided it has enough heatsink to work with.   I think it would be fine with the newer, dual coils, though the deciding factor may be whether it needs more heatsink, such as bolting it so the heat can get into the frame as well as the aluminum cover, or using a more massive aluminum cover.  Just take care to ensure that TIP162 mounting screw is insulated from the tab on the transistor - the transistor's tab can have over 300V on it during firing cycles.

[Barry]

 Nhmaf …  you sound like a proper electronics man. I learn't some electronics during an apprenticeship 35 years ago then moved on to Electrical distribution so I'm more than a bit rusty. I've already found a data sheet for the TIP162 which suggests it will handle more than the 4A the kit is rated at. It says 10A cont' and 15A peak but I don't think it's that simple.  

The kit comes with a plastic bush to insulate the heat sink mounting screw. I took some further precautions by sleeving the screw where it passed through the transistor mounting hole and also painting the heatsink. If you look carefully at the 1st photo you can see where I took the paint off half of the screw head to check it wasn't becoming live.  I Know what you mean about the heatsink size I just made it to fit the space with the intention of seeing how it went.

[nhmaf]

Hi Barry,

Yes, electronics is my business - and yes, the TIP162 can handle 10A continuous, but we generally design products like this to run at no more than approx 75% of full rated capacity to assure better longevity.   It sounds like you know what you're up to also - keep us posted on how it goes.    While I am sure that my old original BMW coil was starting on its way to the bin before I swapped it, I found that the Dyna "brown" dual coil gave much better starts - and this with the standard OEM ignition module.  I think it would work nicely with your amplifier kit when you are ready to update the coils.

[ukzknos]

Barry

Is this kit offered by Maplin the same 'beastie' that you have but with a modified heatsink?

Thanks
Steve

http://www.maplin.co.uk/module.aspx?TabID=1&criteria=usb&ModuleNo=3162&C=SO&U=Strat15

[Barry]

Steve

Yes thats it. I couldn't fit that heat sink under the tank and if I had put it out front near the horn bracket it would have needed to be seriously waterproof.  It's a shame they don't sell it with a suitable enclosure.

[nhmaf]

It definitely appears like the same picture to me.

[tvrla]

I've never built a kit, though I have used the amplifiers on my bikes. They are definitely the way to go.

If I knew of a kit here in the US, I'd build one. I wonder if there's an IC that'll work for this application?

Also, when running an amp, be sure to regularly check the points and lube the rubbing block. If the block didn't wear, the points would last forever. I've thought about modifying the rubbing block with a miniature bearing.

[Julio A.]

What about the newer non points ignition? Do those have different amplifiers?

[tvrla]

The ICU in the newer electronic ignition systems is actually an ignition amplifier. No need to add a second amp unless you're running dual plugs.