Post by theradbaron on Jan 27, 2009 16:13:15 GMT -5
I've always been resistant to switching my old bikes over to any sort of electronic ignition. I like the simplicity and reliability of properly set up points, though the fact that the points burn up so rapidly and need replaced has always had me considering the swap. The thing that always stops me is that if something goes wrong with your ignition far away from home, points are simple to troubleshoot and McGyver to get you home. If some component fails in an electronic ignition, you're a pedestrian. I've been kicking around the idea of a transistorized points ignition for a while, as it seems like a good compromise. In a transistorized points ignition, the points are used to trigger a switching transistor. The current used to fire the plug goes through the transistor instead of the points, so there's no arcing or pitting of the points. What appeals to me the most is that fact that if the switching transistor burns up, you can just bypass the transistor and hook up to the points. The condenser isn't used in the transistor circuit, but if you leave it on the bike, you can reconnect it in the event of a transistor failure. Not that a transistor is likely to fail, I just like the security of a redundant backup ignition. Not to mention that this is probably the cheapest way to upgrade the ignition on an old bike. Probably about $10 per set of points.
I'd put this project on the backburner, but a post about this just came up on caferacer.net and it got me thinking again. Here's the link that was posted:
basilisk.chaosnet.org/motorcycle/diy_transistorized_ignition.html
I did some searchin and found small heat sinks at Radio shack for $2. I've been having a bit of trouble finding the ideal transistor, though. I'm told that the coil will backfeed into the transistor to the tune of a few hundred volts, so a transistor with a high voltage rating is needed. To my knowledge, the transistor must be PNP polarity, which rules out the best transistor I've found (MJ10012). I found two that should work. NTE2329 is rated 200v 15a, and operates to 150 deg. C. MJ1302A has the same specs but will operate to 200 deg. C. However, the MJ transistor would be slightly harder to mount to the heat sink due to its design. Both transistors are about $4-5 a piece. I like to overengineer the things I build, so I'd go with the MJ. Heat will kill the transistor, and the constant switching will cause the buildup of heat, so I like the higher temp rating.
This system should work for any points ignition bike, though for a twin with two sets of points, a transistor unit would be needed for each set.
I haven't built one of these yet, so it's still in the hypothetical stages. I know that the setup has been successfuly used on motorcycles. I imagine that some of the electrical guys on this forum will have some more insight on the matter. I'd really like a transistor that's rated higher than 200v as a safety margin. I plan on building one of these soon, so I'll update the thread as I go.
I'd put this project on the backburner, but a post about this just came up on caferacer.net and it got me thinking again. Here's the link that was posted:
basilisk.chaosnet.org/motorcycle/diy_transistorized_ignition.html
I did some searchin and found small heat sinks at Radio shack for $2. I've been having a bit of trouble finding the ideal transistor, though. I'm told that the coil will backfeed into the transistor to the tune of a few hundred volts, so a transistor with a high voltage rating is needed. To my knowledge, the transistor must be PNP polarity, which rules out the best transistor I've found (MJ10012). I found two that should work. NTE2329 is rated 200v 15a, and operates to 150 deg. C. MJ1302A has the same specs but will operate to 200 deg. C. However, the MJ transistor would be slightly harder to mount to the heat sink due to its design. Both transistors are about $4-5 a piece. I like to overengineer the things I build, so I'd go with the MJ. Heat will kill the transistor, and the constant switching will cause the buildup of heat, so I like the higher temp rating.
This system should work for any points ignition bike, though for a twin with two sets of points, a transistor unit would be needed for each set.
I haven't built one of these yet, so it's still in the hypothetical stages. I know that the setup has been successfuly used on motorcycles. I imagine that some of the electrical guys on this forum will have some more insight on the matter. I'd really like a transistor that's rated higher than 200v as a safety margin. I plan on building one of these soon, so I'll update the thread as I go.
