Sage Gedde Ignition - Buzz coil add-on?

[pmerritt]

Hello everyone,

I have just built a Sage Gedde ignition module published in Model Engine Builder for my Upshur engines. It seems to be working well using a Ford COP coil. Now I would like to add buzz functionality for my hit and miss engine. I have a buzz module that I bought from S/S but killed it in an operator induced grounding accident. Prior to its untimely death, it worked well between the hall sensor and the ignition module. I would like to recreate this in my homemade ignition. Does anybody know where I can find a schematic for one? I know it can be done with a 555 timer chip and have found some ignition related schematics online. However, I don’t understand how/where to incorporate the hall sensor. I am also not entirely sure how the output from the timer should be routed into the single spark ignition circuit. My understanding of electronics is poor on a good day, but I would like to add this to the list of satisfying projects accomplished. I realize I can just purchase a circuit like this but what fun would that be?! Thanks in advance for any help you all can provide.

Peter

[Don1966]

Go to this web site fir the 555 timer circuit!... https://www.electroschematics.com/wp-content/uploads/2013/06/555-Ignition-Coil-Driver-Schematic.jpg

[pmerritt]

Thanks Don! I have been looking at this schematic but am still confused about where the hall sensor input goes. If I understand things correctly, the voltage on the signal leg of the hall drops to ground when the magnet passes the sensor. That drop then tells the transistors in the ignition circuit to charge and fire the coil. My thought is that I should be able to incorporate the 555 timer between the hall and the part of the Sage Gedde ignition that picks up the hall signal. This is based on the fact that the S/S buzz circuit I have fits in that spot. In the schematic you referenced, where does the hall signal go? Would the open collector output then feed the rest of the trigger circuit at the frequency of the 555? I do wish I had a better grasp of electronics  Thanks again for the input.

Peter

[Don1966]

The circuit I posted is free running and acts as a coil driver at a adjustable freqency rate. I gave you link to the site for more information.

Don

You an use something like this circuit Below. There are many You can choose from on the net jusT do a 555 timer search and choose what you want

[pmerritt]

Thanks again Don!! That is exactly what I was looking for. It will be enough to get me started with testing to see if I can get it to work.

Peter


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[pmerritt]

Well I've done some testing... I can build an oscillator that will drive the ignition circuit the way I want it to and I can use the hall sensor to turn the oscillator OFF. This seems to be the exact opposite of what I want. All the google searching I've done leaves me at the same point. I can turn the oscillator off when the magnet passes the sensor which will not give me the series of pulses to the ignition circuit as desired. This makes sense as the hall signal goes from high to low. I know that it is possible to do this, but I can't find the magic nugget of information that I need to get the thing to work in the right direction. I feel like there is something fundamental and obvious that I'm missing here  It seems that I'm a the dangerous state between total ignorance and actually knowing what I'm doing. At this point, abject stubbornness is keeping this project alive. I really need to decide on what engine I want to tackle next and move on... Any advice would be greatly appreciated.

Peter

[Admiral_dk]

If you build Dons first schematic, you could put the output of the Hall Sensor in series with R4 so it only supplies signal-power to the circuit that follows it.

Another posibillity (and probably better option) would be to connect the output of the Hall Sensor parallel over Q1s collector and ground.

I hope this helps you.

Best wishes

Per

[Don1966]

If you want to control the circuit without the timer, put your hall sensor in its place. Disconnect the timer and connect you Hall sensor collector to R4 and It’s emitter to ground. The circuit will be off till the Hall sensor is triggered. The only draw back is the width of the pulse which was preset at 1 milliseconds To turn the coil on. Now the passing of the magnet turns it on and time is how long it’s sits in from of the hall device.
Another way is to put the Hall sensor in series with R3 by lifting it from ground and putting the Hall sensor to produce the ground. The circuit shouldn’t oscillate till it’s grounded.

Regards Don

[Admiral_dk]

Sorry Don, but don't you have it the wrong way round ?
If the Hall-Sensor is On when it see a South-Pole and the magnet only is close when he want sparks - your suggestion will suppress them while the magnet is close and fire when the magnet is away .... as far as I see it ....

Best wishes

Per

[Don1966]

Per I am looking at the hall sensor turning on when the magnetic is in front of it. Other then that it’s an open circuit. Am I looking at his wrong please feel free to correct me. This is for the control of the oscillator circuit which will free run as long as the magnetic is in front of it. As for the first circuit control I mentioned you are correct as far as I can see it. The coil output is active when the circuit opens and the inductive kick hits the coil by the collapsing magnetic field. This output can be amplified by the addition of a capacitor to create a resonance circuit.


Don

[Admiral_dk]

Per I am looking at the hall sensor turning on when the magnetic is in front of it. Other then that it’s an open circuit.

I agree - but this also means that it 'short circuits' the output of the 555 ocsilator to ground when the magnet is in the 'Firing position' - just the opposite of what is required.
I do know that it's possible to get Hall-Effect sensors that are NC and open when they see a Southpole magnetic field - but they are kind of rare .... and would have worked when placed as you suggest.

This output can be amplified by the addition of a capacitor to create a resonance circuit.

YES - and it easily can be an order of magnitude stronger spark, than without 
My first attempt at building an electronic ignitio system in my youth could easily ignite paper put inside the gap on a sparkplug after I found the right value for that particular coil (in that case 560nF 630V if memory serves).

[MJM460]

I wonder if the clue is that the Hall effect Device only triggers the 555.

When I look at the one shot circuit shown on the 555 data sheet, it seems that the input is normally high, and the trigger pulse is a brief low.  When the Hall effect device sees the magnet?  Then the output goes from low to high for a fixed time period, which seems to be what is required to operate the sparking circuit.  It is shown in the little graphs under the circuit drawing on the 555 data sheet.  Does that help?

But I am still  not sure how the back half of the circuit works.

MJM460

[Don1966]

Per I am looking at the hall sensor turning on when the magnetic is in front of it. Other then that it’s an open circuit.

I agree - but this also means that it 'short circuits' the output of the 555 ocsilator to ground when the magnet is in the 'Firing position' - just the opposite of what is required.

Per, sorry for the miss understanding I meant without the 555 timer in the circuit on the first suggestion. By adding the sensor in series with R3 the circuit would free run as long as the sensor is on.

Regards Don

[Admiral_dk]

I specifically referred to Don's first shown schematic and on that the 555 is running as an astable multivibrator (oscillator)- having a 1mS. firing time and an adjustable delay before next auto firing ~ this kind off a trembler, running all the time.
The circuit the the right of the 555 is an current amplifier where the right most transistor is a high voltage device (and they usually requires quite a bit of current as input).

My first suggestion cuts the signal to the current amplifier when a spark isn't required and my second suggestion shorts the firing signal for the duration of not wanting fire.
None of them gives a perfect firing timing as they haven't got any influence on where the oscillator is in it's sequence, but if the firing is as rapidly as the coil can sustain it will not matter on a slow running engine - but would be a problem over a certain RPM ....

I hope that I have explained it in an understandable way (I'm an Electronic Technician by education and profession). If not, please ask and I'll try to do better 

[Don1966]

I wonder if the clue is that the Hall effect Device only triggers the 555.

When I look at the one shot circuit shown on the 555 data sheet, it seems that the input is normally high, and the trigger pulse is a brief low.  When the Hall effect device sees the magnet?  Then the output goes from low to high for a fixed time period, which seems to be what is required to operate the sparking circuit.  It is shown in the little graphs under the circuit drawing on the 555 data sheet.  Does that help?

But I am still  not sure how the back half of the circuit works.

MJM460

MJM in the free running circuit I first listed Q1 is turned on by R4 which clamps the base of Q2 to ground so no current flows through Q2 till the timer goes Low to clamp Q1 base to ground turning it off and allowing R4 to bias Q2 on and current flows through the coil for 1 millisecond then the coil fires from the collapsing magnetic field.

Regards Don