Nice coil and ignition

[Rudy from Norway]

Hello my friends,
Just wanted to tel you about my new ignition system for my Farm Boy hit'n miss engine. I was looking for a suitable coil for it and found this:

http://www.icstation.com/15kv-high-...ule-18650-core-transformer-suite-p-12099.html

This is a very cheap and small coil and it actually works. Paid $5 shipped. It's a module that generate s constant arc, but we just want to use it as a single (or multiple) spark coil so you won't need all the components. Just use the coil and maybe the pcb to hold it. The low voltage side has two windings, but we just use the one with the thickest wires.

I also made up an ignition driver for it. I do electronic development for a living, so I can do such things. It is a buzz ignition, giving a series of sparks and reduces the number of sparks as the rpm increases. It is experimental, but at least it works for the low rpm hit'n miss engine. Haven't tested it on higher rpm engines. The output transistor is a bit overkill (it is for car coils), but it is specially designed for ignition applications and won't brake down. You can use either a hall sensor or points. It is a lot of various hall sensors to chose from, I tested several and found the one in the schematic to be fine. I doesn't work well over 6V, but it generates a strong spark.
So if you can do a little soldering, it is worth a try.
This coil will work fine with just points or another driver too.

Rudy

 

[Rudy from Norway]

Found another source for this coil:

https://www.ebay.com/itm/15KV-3-7V-...392363?hash=item25f1ac52ab:g:H9wAAOSwVQ5Z5Cc7

Rudy

 

[bmac2]

Rudy, thanks for the info that looks like a nice compact setup. For us Canadians I found them on Amazon.ca. 2 for $10.69 (Prime)

https://www.amazon.ca/Voltage-Gener...keywords=15kv&qid=1558241056&s=gateway&sr=8-1

Or a single for $4.54 (free shipping)

https://www.amazon.ca/FidgetFidget-...eywords=15kv&qid=1558242126&s=gateway&sr=8-37

Do you think they will ever get someone to proof read the descriptions?

 

[bruedney]

Or you could get it from here
https://www.aliexpress.com/item/328...lgo_pvid=3de37970-d191-4ca3-8433-6b0a2928450d for only $0.43 and a small amount for shipping

 

[Rudy from Norway]

Thanks bruedney, even better!
Have you tested it? Mine works very well on my low compression Hit and Miss engine. Can´t tell if it creates enough energy for higher compression engines.
Rudy

 

[Rudy from Norway]

bmac2, I believe we are on our own here. This coil pops up many places and looks like a generic component.
Rudy

 

[IC-man]

Hi every one,
I have just received 3 of these units ( very cheap at £5 delivered) and have wired it up to my existing home made transistor system (not the one mentioned in this thread) and an can confirm it does work, although the spark was not as good as either a normal 12 v car coil, minimotor coil or a COP coil,IMO.
I have yet to run an engine with this coil but will "give it a go" next week sometime.
I have been trying it with just the one winding (the thick wires) not sure why this was suggested. perhaps someone can shed some light on this.
Anyway i will try both windings later.
If this coil works well then I think it would solve a lot of space problems because the coil could be included on the main board.
I await your comments.
Graham

 

[Rudy from Norway]

Glad it worked out for you to Graham. The winding with thinner wires is for feedback if you want it to generate a constant arch. Just leave it not connected. I believe this is a nice model engine coil, both the price and size is nice.
I have been running my Farm Boy on the setup I show in the diagram above, for a while now and it starts on the firt flipp every time.
Rudy

 

[cdn flyr]

I have just discovered this thread and have 5 of these kits coming in the mail. Would you believe 5 for under $10US delivered? I am not an electronics guy but it looks to me like the spark frequency is determined by the puncture and recovery of the UF4007 diode triggering the thryistor. This is very similar to the earlier Bill Schmidt transistor model aero engine ignition. Could some of you electronics experts please comment on the feasibility of just replacing the diode with ignition points? My intended use is for a low speed hit and miss engine.

 

[dsage]

I have just discovered this thread and have 5 of these kits coming in the mail. Would you believe 5 for under $10US delivered? I am not an electronics guy but it looks to me like the spark frequency is determined by the puncture and recovery of the UF4007 diode triggering the thryistor. This is very similar to the earlier Bill Schmidt transistor model aero engine ignition. Could some of you electronics experts please comment on the feasibility of just replacing the diode with ignition points? My intended use is for a low speed hit and miss engine.

What schematic are you looking at?

 

[cdn flyr]

Sorry, it is the schematic in the seller's description in the Ebay link of Rudy's post #2 above

 

[dsage]

Ok. I see the schematic now. (buried pretty deep in that product listing).
The circuit is not based on the breakdown of the diode. What you have is a self oscillation circuit. The coil has a feedback winding that drives the base of the transistor. The diode is there to rectify the pulse coming back from the winding so it will drive the transistor and provide feedback to sustain oscillation.
The pulse coming back could be quite high voltage so the resistor is there to limit the base current.

 

[cdn flyr]

Thanks dsage. I think I will just be able to use the transformer, board and transistor; and drive the base thru the points and a resistor with 4v battery voltage. Only the heavier primary coil will be used. this is exactly the Bill Schmidt circuit. I am travelling now and will not be home in my shop until mid March to try this out.

 

[Gordon]

I am not familiar with electronics but could this be used as a coil on something like a TIM6 circuit or would it require additional parts and circuit?

 

[dsage]

Hopefully canfly will be successful. I'm skeptical.
If his experimant works then a TIM6 circuit should work without any changes.

 

[cdn flyr]

Please note: my handle is changed from canfly to cdn flyr. Attached Figure 1 is the original kit schematic. Figure 2 is the proposed mod to make it a complete ignition module. the feedback winding is not used. The N20 transistor is triggered by a 4v, 33milliamp signal to its base thru the engine's ignition points. Kit instructions say power voltage may be increased to 12v max with corresponding increased resistance in the base circuit. Apologies for the poor quality of the attachment as I am travelling and have limited resources. Next post will be of Bill Schmidt's model aero engine ignition circuit. You will see a remarkable similarity of his circuit to the proposed one of Figure2, except he used a PNP TIP42 transistor, whereas the kit uses an NPN N20.

 

[cdn flyr]

attached is Bill Schmidt's model aero engine ignition circuit