S / S CDI ignition system

[Rustkolector]

I routed out my wood base to hold the ignition module and battery back. Both are installed using red 3M heavy duty double faced tape. It is about 1/16" thick, soft, and holds very well. I also use it to hold pieces to the lathe face plate. I have run my unventilated system for hours on end at shows with no ill effects, or overheating.

Jeff

 

[cfellows]

I was doing some troubleshooting yesterday on my plumbing engine (wouldn't start) and I pulled the plug out to see if it was firing. I discovered that the S / S CDI ignition module fires twice, once when the switch closes and again when it opens. Has anyone else observed that? Just wonder if that's normal operation. I'm using a micro-switch instead of the hall affect transistor...

Seems like that could potentially be problematic if my ignition is firing at the beginning of the compression stroke, where the switch closes and at the top of the compression stroke when it opens.

Chuck

 

[putputman]

Chuck, I was having the same problem when I was using points on my Tiny I.C. engine. I talked to Roy Sholl about it and he said it is not supposed to do that and he couldn't understand why it was happening. I made a video of it for him to look at but he said he couldn't bring it up on his dial-up internet.

I felt it was a wasted spark but I couldn't control the timing with it that way. I finally made a new cam with a very short contact time and rotated it so the first ignition was at TDC and the 2nd would be during the power stroke where it wouldn't hurt anything. It was just too hard to control.

I switch to the Hall Effect & Magnet and the engine took off and has run good every since. I just assume I had a defective unit but being it ran OK with the Hall, I wasn't going to pursue it any more.

I think you should contact Roy and explain it to him. He obviously has a problem that should be fixed.

I hope he is at N A M E S so I can talk to him a little more about the problem. I plan to buy some more units, but I would like them to run with breaker points.

 

[doc1955]

I noticed the same what I've done to try and address this was to do the same made the trow on the cam more and have a larger point gap to the point where the points just touch this creates a almost zero dwell for the points being closed. It seemed to help a lot with the double fire.

 

[ghart3]

Just a thought. If there wasn't a clean break when the points open maybe the ignition module sees a open - close and open again as the points are opening. It is advertised "MAXIMUM SPARKS PER MINUTE = 12,000"

 

[cfellows]

Just a thought. If there wasn't a clean break when the points open maybe the ignition module sees a open - close and open again as the points are opening. It is advertised "MAXIMUM SPARKS PER MINUTE = 12,000"

Yeah, I wondered about that too. Thought maybe the switch was bouncing.

Chuck

 

[putputman]

Chuck, when I talked to Roy, he suggested it might be a bounce. I took a video while turning the engine over by hand. It is not a very good video but it does show that a spark occurs when the points make and again when they brake.

I'm convinced it isn't bounce.

 

[cfellows]

Yeah, I see what you mean on the video. I was turning my engine over by hand, pretty slowly when I detected the double spark.

Chuck

 

[putputman]

Chuck, I have been wondering if you ever resolved the double spark problem. Did you talk to Roy Sholl about the problem?

I finally got my drag saw up & running with the Red Wing engine driving it. Now I want to paint & remount all the components on a new frame. At the same time I was thinking to switch the ignition system from the old ford coil to the S / S CDI unit but I would like to still use the point system rather than Hall effect.

I will be at NAMES next week and will talk to Roy if he is there. I was hoping you have contacted him also so he realizes mine was not the only unit that had a double spark.

 

[cfellows]

Arv, I've not contacted Roy about the double spark problem. Near as I can tell, it's not causing a problem. However, feel free to give Roy my name if you'd like. I'm using a microswitch activated by a cam.

Chuck

 

[cfellows]

Arv, did you get a chance to talk with Roy at NAMES about the double spark issue on his coils?

Chuck

 

[Ctmouse]

I'm in need of some direction as I need a new ignition System for this mini Tractor Motor it has a set of points Condenser and a coil from a lawn mower (the coil is bad) this was used to provide spark to a NKG CM 6 Plug I was using a small 12 volt battery for the coil Which I believe I fried the coil! I'm in the begining stages trying to bring this back to Life.
This was built my an uncle way back in the day and has sat in the basement for decades now. I really Don't have much history on it other than it did run back then. after some research it appears to be a version of a HUMBLEY Oil Pull tractor. I am hoping to replace the ignition and get it to run again. I believe this would be just an air cooled motor that has forward and reverse capabilities. ant help on this project or suggestions would be greatly appreciated.

thx Rick

 

[bluejets]

Did you see my writeup from a few months back?
https://www.homemodelenginemachinist.com/threads/model-engine-cdi-easy-and-cheap.31128/#post-322284

 

[rsholl]

Arv, did you get a chance to talk with Roy at NAMES about the double spark issue on his coils?

Chuck

Hi Chuck and fellow model builders,

NAMES was crazy busy on Sat. so I'm not sure who all I talked with.
To address the problem Chuck is having and also with some reed switches and points set ups. My CDI is triggered via a logic circuit. What that means is, the WHITE wire, by what ever means, must be pulled to ground. When it is released the CDI fires the coil. What I have heard and seen over time is when the CDI fires when the points close, it is due to point bounce OR the points MOVING when they close. This bounce or rubbing action can only be seen on an Oscilloscope. The logic circuit in the CDI is very sensitive and can detect closing and opening in the micro second and possibly even nano second range. So, any switch that is not 100% clean when they make and break can trigger the CDI. For the past year, I have instructed anyone with a points issue to set the point gap in the .003" range. The CDI does not have dwell time like the old Kettering system does. My logic being, if the points don't have to move far, then there is less chance they could bounce or slide together. I have also tossed out the idea of using a switch/points that are NORMALLY CLOSED and open only when you need the spark. The CDI doesn't care which state it is in most of the time, it just needs to change. The WHITE wire is logic HIGH and if it is held in the ground condition and only released when a spark is needed it should fire the engine reliably. This doesn't mean it won't fire when they close again but it would be after the correct spark timing and should not be a problem. Now that the new Version CDI is finalized I hope to be able to spend some time looking at remedies for the erratic operation of some micro-switches and points. I hope a small value capacitor on both the micro-switch and some points setups might eliminate the erratic firing. On most electronics with mechanical switches there is software that debounces the switch and that includes push button switches. I could program a module similar to the one used to convert our single spark to a buzz coil but that would be over kill. I am always glad to get feed back from anyone and know I have not kept up as well as I should have. It has been a struggle over the past 2-3 years with the CDI because manufactures kept obsoleting parts. With the new version CDI, I am having the transformer wound here in Ohio and I am hand soldering the components on the board so now we have complete control over the manufacturing of the CDI. If anyone has tried the normally closed points set up, I would definitely like to hear from you. I do get email updates when someone posts and now I hope to be able to keep up with what's going on. I hope this sheds some light on how the CDI operates. The reason we don't see this with the hall sensor is because it is not mechanical and by design it is in one of two states, either ON or OFF, nothing in between.

Regards,
Roy Sholl

 

[bluejets]

Hi Chuck and fellow model builders,

NAMES was crazy busy on Sat. so I'm not sure who all I talked with.
To address the problem Chuck is having and also with some reed switches and points set ups. My CDI is triggered via a logic circuit. What that means is, the WHITE wire, by what ever means, must be pulled to ground. When it is released the CDI fires the coil. What I have heard and seen over time is when the CDI fires when the points close, it is due to point bounce OR the points MOVING when they close. This bounce or rubbing action can only be seen on an Oscilloscope. The logic circuit in the CDI is very sensitive and can detect closing and opening in the micro second and possibly even nano second range. So, any switch that is not 100% clean when they make and break can trigger the CDI. For the past year, I have instructed anyone with a points issue to set the point gap in the .003" range. The CDI does not have dwell time like the old Kettering system does. My logic being, if the points don't have to move far, then there is less chance they could bounce or slide together. I have also tossed out the idea of using a switch/points that are NORMALLY CLOSED and open only when you need the spark. The CDI doesn't care which state it is in most of the time, it just needs to change. The WHITE wire is logic HIGH and if it is held in the ground condition and only released when a spark is needed it should fire the engine reliably. This doesn't mean it won't fire when they close again but it would be after the correct spark timing and should not be a problem. Now that the new Version CDI is finalized I hope to be able to spend some time looking at remedies for the erratic operation of some micro-switches and points. I hope a small value capacitor on both the micro-switch and some points setups might eliminate the erratic firing. On most electronics with mechanical switches there is software that debounces the switch and that includes push button switches. I could program a module similar to the one used to convert our single spark to a buzz coil but that would be over kill. I am always glad to get feed back from anyone and know I have not kept up as well as I should have. It has been a struggle over the past 2-3 years with the CDI because manufactures kept obsoleting parts. With the new version CDI, I am having the transformer wound here in Ohio and I am hand soldering the components on the board so now we have complete control over the manufacturing of the CDI. If anyone has tried the normally closed points set up, I would definitely like to hear from you. I do get email updates when someone posts and now I hope to be able to keep up with what's going on. I hope this sheds some light on how the CDI operates. The reason we don't see this with the hall sensor is because it is not mechanical and by design it is in one of two states, either ON or OFF, nothing in between.

Regards,
Roy Sholl

Why not use tried and true "hardware debounce".
The problem you encounter with a mechanical switch is not "new" or unknown, in fact the solution has been around almost forever.
Below is a link to "hardware debounce" circuit and if the output logic does not suit your application, simply add an inverter transistor stage, simple.

Look at hardware debounce about half way down the page, operation of it is explained under the circuit diagram.

http://dduino.blogspot.com/2012/03/arduino-button-debouncing.html

Another source for explanation is in this video.

 

[editor123]

I was doing some troubleshooting yesterday on my plumbing engine (wouldn't start) and I pulled the plug out to see if it was firing. I discovered that the S / S CDI ignition module fires twice, once when the switch closes and again when it opens. Has anyone else observed that? Just wonder if that's normal operation. I'm using a micro-switch instead of the hall affect transistor...

Seems like that could potentially be problematic if my ignition is firing at the beginning of the compression stroke, where the switch closes and at the top of the compression stroke when it opens.

Chuck

You could be getting switch bounce if you are using a microswitch. But I see that Roy has already suggested that.

 

[rsholl]

Why not use tried and true "hardware debounce".
The problem you encounter with a mechanical switch is not "new" or unknown, in fact the solution has been around almost forever.
Below is a link to "hardware debounce" circuit and if the output logic does not suit your application, simply add an inverter transistor stage, simple.

Look at hardware debounce about half way down the page, operation of it is explained under the circuit diagram.

http://dduino.blogspot.com/2012/03/arduino-button-debouncing.html

Another source for explanation is in this video.

bluejets,

That does not work on our CDI. The WHITE wire is already logic high and feeding any voltage into it is a NO, NO. Most standard automotive points work well if the gap is kept small, in the range of 3 to 5 thousands of an inch. For reed or micro switches you would have much better luck using a NORMALLY CLOSED type switch. If you already have a standard NORMALLY OPEN type switch, just set it up so it is activated (switch closed) and release it when you want to fire the CDI. Another option would be to add the Buzz Module (which I checked and see I do not have listed but will do that next) to an existing single spark cdi and convert it to a Buzz type CDI. The timing would have to be changed slightly as the buzz module will make the CDI oscillate or buzz as soon as the points close and stop when they open. This should not be a major problem for most engine. If there were enough interest, I could program the little circuit board I use for the buzz module and make it de-bounce noisy switches.

 

[bluejets]

That does not work on our CDI. The WHITE wire is already logic high and feeding any voltage into it is a NO, NO.

You could simply use an open collector to my original suggestion and that would suit your needs.

 

[rsholl]

bluejets, I agree on using the open collector and that is what our hall sensor is, plus it plugs straight into the cdi with no extra circuitry.

 

[bluejets]

bluejets, I agree on using the open collector and that is what our hall sensor is, plus it plugs straight into the cdi with no extra circuitry.

Yes, I am well aware of what a hall effect is.

Very confusing ...I thought the discussion was about using points. ...??