They can get very hot and even cause a fire. De-soldering is a pain.īe sure to mount the transistor on a heat sink. Go for the ones that are connected with long leads and just cut them off. Tear apart almost any electrical device and you will find them. Power transistors are the bigger, sort of square ones versus the small round cans or round plastic with a flat area.

I now have almost 50 transistors ready for use. I happened to have purchased a junk bag of various transistors(about 400) for two dollars and started testing them in my circuit. That made me think, why not other similar transistors. When the store ran out they sold me a different but electrically equal substitute. The transistor specified is a NTE 332 which I used several times. There is probably a thousand ways to operate contacts.Ī couple of comments on parts. In my application the cam is simply a round head screw on a small disk. B is one where a shaft rotates a cam to make contact. A is the one I described above and is specific to the engine. It instantly moves back, breaks the base ground connection which turns off the transistor and of course causes the magnetic field in the coil primary to collapse and pop goes the spark plug.īelow is a drawing showing a couple of methods I have used to operate contacts. The rod is electrically grounded to the engine body and then the ground wire.Īt top dead center the rod jumps forward and touches the Base ground contact, which turns on the current flow thru the transistor. The paper clip extends down to a brass contact on the rod that operates the valve. The blue thing is just a piece of plastic to hold the paper clip and keep it from grounding constantly. The second is a close-up where you can clearly see the connection to the paper clip contact. The white wire is the Base to ground wire and the black wire is ground to the body of the engine. In the first picture the yellow wire is the lead to the plug. Any metal contact should work.Ībove is my latest hit-miss engine. I personally prefer small paper clips although I once used a piece of 22 g electrical wire. So where the diagram shows a set of points, substitute any kind of simple contact. That is why you do not need special points.

There is only a very small amount of voltage and current passing from Base to ground so no arcing occurs. The Base is turned on and off by connecting it to ground through the 10 ohm resistor. Think of the Base as the handle on a faucet, turn it on current flows, turn it off it stops. As noted on the diagram different transistors use different arrangements for the connections. The connections are marked E C B on the transistor. Current passes from the Emitter to the Collector depending on the bias voltage of the Base. As I understand it DC current from the battery feeds to the transistor and is connected to the Emitter.

The second picture is a close-up of the transistor connections.

Hit and miss engine coil wiring diagram