Another transistor ignition question

[Gordon]

I have been doing quite a bit of working with transistor ignitions lately. I have a Howell and a S/S system and I am trying to use a hall sensor. The instructions say that the plug fires when magnet is past the sensor. Both of these systems produce a spark when the magnet energizes the sensor and again when it is past the magnet. This means that I am getting a spark twice every time the magnet comes around about 15° apart. Any idea what I am doing wrong. Electronics is not my area of expertise.

I had this engine running great using the S/S unit so I figured that it was a good engine to experiment on so I tried it with the Howell unit and have not been able to get it to run again using either ignition. I have tried working on both fuel and ignition and can occasionally get the engine to fire once but cannot get any consistent run. Very frustrating.

 

[gld]

I may be wrong here, but I think you are suppose to use the North pole of the magnet to trigger the hall sensor.

You may have fried the hall. They can be destroyed very easy.

 

[RichD]

I think you should be able to wave a metal object past the sensor to create a "test" spark. Have you tried this?

What sounds odd to me is the fact that it ran fine before and now it doesn't with either unit.

What part(s) is in common with both units?
Spark plug
Coil
Magnet
Power Transistor
Ground wire
Power fuse
Sensor

Rich

 

[Gordon]

Actually it requires south pole.

The Howell unit requires a separate coil but the S/S has a built in coil. I can get a spark by passing the magnet over the sensor with either unit. I burned out the sensor so I have replaced that. Forgot to hook up the ground wire so then it grounds through the sensor. It is activating the ignition module with either unit. Actually get a spark at the plug at least when the spark plug is outside of the engine.

I have the magnet on the perimeter of an aluminum disk on the crank shaft. I am wondering if that may be the problem because the magnet is approaching the sensor on an arc.

The engine ran for perhaps thirty seconds after I started changing ignitions systems and then died never to run again.

 

[Cogsy]

I have only had experience with the RXCEL type ignitions, but I had my magnet set up the same way as you and it sparked just fine.

I also had an issue of the unit making a nice big blue spark when checking the plug out of the engine, but no matter what I did I only got the occaisional pop out when trying to start it. Finally, after much mucking around and getting nowhere, I put fresh batteries in the ignition and the engine fired straight up. It seems the batteries had enough juice to throw sparks at the slow speed of checking spark, but couldn't keep up when spinning the motor over fast. Hopefully this is your problem too as it's an easy fix.

 

[tornitore45]

I bought and used two S/S modules.

The first would fire when the Sense lead open and also when it closed.
I was surprised but I surmised, without verification, that instead of using an SCR they may have used a TRIAC. TRIAC are triggered with bot positive and negative edges.

The second unit I received would only trigger on the Sense lead opening.

Furthermore, when using points, the contact may bounce producing a series of sparks.
Therefore is a good idea to time the spark with the first active transition, that is when the cam or the magnet generate the first circuit opening or closing.
If a second spark is generated soon after it will be during expansion and would not hurt, on the other hand an early spark would not be very good.

If you are electronically adept, there are modifications you can make to the circuit to guarantee one spark event at the right transition but you do the modifications at your risk.

 

[Gordon]

I have two S/S systems. I have one which I was using on this engine and suddenly quit working. Finally determined that I was getting arcing between the spark plug wire and the ground on the coil therefore I was getting a weak spark. I finally tried the other S/S system and that works fine. I ordered a new coil assuming that the coils was defective. I will wait and see.

I still have been playing around the Howell system. I am getting a spark but I am not sure if it is adequate. I think that my problem is in not having a proper coil to use with the Howell kit. I have a coil over plug coil. This coils has .7 ohm primary resistance and the Howell site says minimum of 1 ohm. A six volt auto coil has 1.3 ohm but is a huge unit with a large current draw to charge it. I still have not found a proper coil. Open to suggestions.

As usual it does not take long for me to get beyond my knowledge.

 

[tornitore45]

If the COP suites you dimensionally, then you can add 0.33 or 0.47 Ohms resistor. one rated 7 Watts will do it but do not allow the engine to stop with the points (or transistor) ON and the Power ON or the coil and resistor will overheat.

 

[Gordon]

The latest results: I finally got the Howell transistor ignition working. The problem seems to be inadequate battery. I was trying to use the large 6 volt lantern battery, the 5" long one. I had tried my 6 volt rechargeable but it also was not working but I finally determined that I had a bad connection. I fully charged the battery and rechecked all connections and now that is working.

On the S/S CDI ignition as I said the one unit worked and the other unit did not work because of arcing across the coil. I just received a new coil so I will replace that and see what happens.

I have to give a shout out to Roy Sholl at S/S. I talked to him on the phone and he was most helpful. I ordered a new coil and some other parts from his website and asked in an email how to hook it up because the defective coil was four wire and the new one is three wire. He refunded my money for the coil and sent me a CD from his kit showing how to hook it up. The refund was not necessary because the original unit was a few years old and certainly well beyond warranty.

I will probably end up converting some of my older engines to the CDI ignition. It is very compact and works from AA batteries.

 

[Cogsy]

Slightly different circumstances to what happened with me but essentially I called it back in post #5 (pats himself on the back). Glad it worked out for you.

 

[tornitore45]

Roy Sholl is a good guy to do business with.

I copied the idea from Chuck Fellow and built a box encasing the S/S CDI; the Switch, and a 4 AA battery holder, plus a switch to select the firing edge polarity.
Connectorized the sense (3 pins) and brought out both HV wires floating to be able to run single cylinder or twins with a wasted spark system.

Now I can share one ignition box among several engines.
Of course dis does not work if you are installing the engine on something that moves.