Driver wiring diagram for ignition coil project?

Thread Starter

clone477

Joined Oct 3, 2008
30
Good morning everyone, I’m looking for some help to make an ignition coil driver using this adjustable frequency PWM controller. I have a diagram, but not sure of the value of components to use for resistors and transistor. This is for some experimentation with resonant coils and other projects that require hv dc pulse with controllable frequent and voltage(12v-16v). I have attached a link to the module I am using and a picture of the diagram. I do want to use a PNP transistor as in the diagram also. Can anyone help guide me with components? Appreciate any help.

https://www.amazon.com/PEMENOL-Gene...=B07W229NVP&psc=1&ref_=pd_bap_d_grid_rp_0_1_iIMG_9395.jpg
 
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LowQCab

Joined Nov 6, 2012
4,300
What is the purpose of this project ?
What would You like the outcome to be ?

The Circuit shown does not have any provisions for limiting the Current drawn by the Coil.
If You want to be able to maximize the Power of the Spark,
and not burn-up the Coil, or any other components,
then You will need some sort of "Dwell" Control.

I recommend a Current-Based-Trigger-Circuit that will create some consistency of operation.

A PWM Signal is not a very good way to control an Ignition-Coil,
although, You might get away with it just the same.

What sort of control do You want over when, and how often, the Coil fires ?
.
.
.
 

Reloadron

Joined Jan 15, 2015
7,580
First I suggest you give this a read. This runs well with the above post:
The Circuit shown does not have any provisions for limiting the Current drawn by the Coil.
If You want to be able to maximize the Power of the Spark,
and not burn-up the Coil, or any other components,
then You will need some sort of "Dwell" Control.
Enter the now seldom seen ballast resistor. They were easily spotted on the firewall of most pre 1970 cars. Generally ceramic resistors with the nichrome wire coil obvious. The link I posted covers this and features those older (like me) ignition systems. You may also want to note that while the battery voltage and ballast resistor were on the + (positive) side of the ignition coil the switching (breaker points) were switching the - (negative) side of the coil.

Today if I wanted to do what it seems you want to do rather than a PNP transistor using high side switching I would consider using a N Channel MOSFET like for example a FQP30N06L and doing low side switching of my coil. Much like the breaker points did years ago. Consider also that typical coil current on those ignition systems was about 5.0 Amps so your ballast resistor needs to dissipate considerable power which is why ceramic resistors are used. Using a logic level MOSFET allows easy interface to your signal source. Make sure if you use this approach you place a 10K resistor between MOSFET gate and ground since we really want a fast shut off on the MOSFET. A fast fall time is what makes the coil spark. :)

On an unrelated footnote here years ago I played around quite a bit with those old automotive ignition coils. While it was only at mains frequency (60 Hz for me) I would drive an old ignition coil using a common light dimmer triac circuit as used with incandescent bulbs. I had some old clear 120 volt large incandescent bulbs. Made an aluminum foil cap for the bulbs and taped it to the top of the bulbs. Connected the coil HV to my caps and coil ground to bulb base. You get a lightening show inside the bulb. Turn out any ambient light and it's a pretty cool effects show that I would photograph. Using different shutter speeds got some interesting pictures. :)

Ron
 
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Thread Starter

clone477

Joined Oct 3, 2008
30
What is the purpose of this project ?
What would You like the outcome to be ?

The Circuit shown does not have any provisions for limiting the Current drawn by the Coil.
If You want to be able to maximize the Power of the Spark,
and not burn-up the Coil, or any other components,
then You will need some sort of "Dwell" Control.

I recommend a Current-Based-Trigger-Circuit that will create some consistency of operation.

A PWM Signal is not a very good way to control an Ignition-Coil,
although, You might get away with it just the same.

What sort of control do You want over when, and how often, the Coil fires ?
.
.
.
Thanks for the response, it will be powered by a DC adjustable power supply, so I can control voltage and current. I really want frequency control that's why I bought and liked the simplicity of that driver from amazon. This is going to used to test different air core/ferrite core resonant transformers.
 

MaxHeadRoom

Joined Jul 18, 2013
28,829
How can you keep the input and output common (chassis GND-Earth GND) isolated when you are using the older style of coils that share a common point.?
If you want a isolated version, obtain the current style used which are known as wasted spark coil versions and the two windings are isolated from each other.
With the circuit shown, the secondary Hi-voltage cannot complete the circuit.
 

shortbus

Joined Sep 30, 2009
10,049
Enter the now seldom seen ballast resistor. They were easily spotted on the firewall of most pre 1970 cars. Generally ceramic resistors with the nichrome wire coil obvious.
The ballast resistor was still there until they started to use the HEI in GM vehicles. The reason people think it wasn't used is because it was hidden in the wiring harness. The running, not starting, coil feed was made with stainless steel wire not copper. The resistance of the stainless wire, to match the ballast resistor value, was doubled up in the harness because the distance was so short.

When they switched to the HEI they also had to feed the distributor 12V all of the time.
 

shortbus

Joined Sep 30, 2009
10,049
Good morning everyone, I’m looking for some help to make an ignition coil driver using this adjustable frequency PWM controller.
The easiest way would be to use your PWM to a GM HEI module and an HEI coil. http://gpzweb.s3-website-us-east-1.amazonaws.com/Ignition/HeiModules/HeiModules.html The signal from the frequency generator would go to the terminal that would normally come from the distributors reluctor wheel pickup.

Using the module will isolate all of the rest of your circuit. Using the HEI coil allows it to be powered from 12V without any ballast resistor. There are 2 different type HEI coils, one is the round type the other is the one that looks like a transformer and fits the top of the distributor cap, the round one is easier to wire up and mount.
 

MaxHeadRoom

Joined Jul 18, 2013
28,829
This is the wasted spark one I recently used for an E-fence, and similar to Ron's suggestion I used a N-ch Mosfet to fire it.
Cheap at an auto wrecker.


1674750829866.png
 
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bradrs

Joined Jan 23, 2023
17
Today if I wanted to do what it seems you want to do rather than a PNP transistor using high side switching I would consider using a N Channel MOSFET like for example a FQP30N06L and doing low side switching of my coil. Much like the breaker points did years ago. Consider also that typical coil current on those ignition systems was about 5.0 Amps so your ballast resistor needs to dissipate considerable power which is why ceramic resistors are used. Using a logic level MOSFET allows easy interface to your signal source. Make sure if you use this approach you place a 10K resistor between MOSFET gate and ground since we really want a fast shut off on the MOSFET. A fast fall time is what makes the coil spark.
Switching the low side like that makes more sense.

That FET breaks down at 60V, right? Unless I am missing something on the design, won't the coil - spike a good bit higher than that when it fires? I remember with HEI it is in the 300+V range, and I think everything else is a good bit higher than 60V too. Clamping the coil negative to a lower voltage was one method I've used in the past to stop a spark for rev limiters. I think those clamped in the 30-50V range.
 
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bradrs

Joined Jan 23, 2023
17
The easiest way would be to use your PWM to a GM HEI module and an HEI coil. http://gpzweb.s3-website-us-east-1.amazonaws.com/Ignition/HeiModules/HeiModules.html The signal from the frequency generator would go to the terminal that would normally come from the distributors reluctor wheel pickup.

Using the module will isolate all of the rest of your circuit. Using the HEI coil allows it to be powered from 12V without any ballast resistor. There are 2 different type HEI coils, one is the round type the other is the one that looks like a transformer and fits the top of the distributor cap, the round one is easier to wire up and mount.
HEIs are cheap and easy. The one thing to watch out for, is that they(mostly) current limit by bringing the coil driver out of saturation. So excessively long dwell signals or high voltage to the coil could overheat the module. A scope probe on the coil - can show that pretty easily though.

Some of the cheaper HEI modules that are flooding the market now have unpredictable behaviour in the current limit mode. I don't remember the details on it other than that I saw an oscillation, but it would probably mess up any testing you do.
 

Reloadron

Joined Jan 15, 2015
7,580
Switching the low side like that makes more sense.

That FET breaks down at 60V, right? Unless I am missing something on the design, won't the coil - spike a good bit higher than that when it fires? I remember with HEI it is in the 300+V range, and I think everything else is a good bit higher than 60V too. Clamping the coil negative to a lower voltage was one method I've used in the past to stop a spark for rev limiters. I think those clamped in the 30-50V range.
You use a flyback diode across the MOSFET similar to this circuit.

IGN Coil Driver.png

The drawing shows a 555 used as an oscillator but you can drive the MOSFET with any 5.0 volt source to the gate. I would, as mentioned earlier include a 1.0 Ohm ballast resistor.

Ron
 

MaxHeadRoom

Joined Jul 18, 2013
28,829
You use a flyback diode across the MOSFET similar to this circuit.
The drawing shows a 555 used as an oscillator but you can drive the MOSFET with any 5.0 volt source to the gate. I would, as mentioned earlier include a 1.0 Ohm ballast resistor.
That is very similar to the method I used, except the primary and secondary are kept isolated, one reason for using waste spark coil.
Also a 6 pin Picmicro was used.
 
Good morning everyone, I’m looking for some help to make an ignition coil driver using this adjustable frequency PWM controller. I have a diagram, but not sure of the value of components to use for resistors and transistor. This is for some experimentation with resonant coils and other projects that require hv dc pulse with controllable frequent and voltage(12v-16v). I have attached a link to the module I am using and a picture of the diagram. I do want to use a PNP transistor as in the diagram also. Can anyone help guide me with components? Appreciate any help.

https://www.amazon.com/PEMENOL-Gene...=B07W229NVP&psc=1&ref_=pd_bap_d_grid_rp_0_1_iView attachment 286096
There is a guy on youtube using 555 timer to drive the ignition coil...although in his video driving cop ignition coil i am pretty sure it also work for the centralized ignition coil since there is MOSFET driving the transformer to spark inside the unit...and of course exactly as you wanted it can control the speed of the spark to ignite by placing potentiometer between pin 7 and 6 of the 555 timer
 

Reloadron

Joined Jan 15, 2015
7,580
That is very similar to the method I used, except the primary and secondary are kept isolated, one reason for using waste spark coil.
Also a 6 pin Picmicro was used.
Yes, pretty much the same. I am tempted to wander out to the garage where I think I have a few motorcycle coils for my bike and try things out.

Ron
 

MaxHeadRoom

Joined Jul 18, 2013
28,829
Yes, pretty much the same. I am tempted to wander out to the garage where I think I have a few motorcycle coils for my bike and try things out.

Ron
On the waste spark versions, I used one of the two plug lead connections for the earth Common for the fence. The other of course, the HV.
 

Danko

Joined Nov 22, 2017
1,857
Good morning everyone, I’m looking for some help to make an ignition coil driver using this adjustable frequency PWM controller. I have a diagram, but not sure of the value of components to use for resistors and transistor. This is for some experimentation with resonant coils and other projects that require hv dc pulse with controllable frequent and voltage(12v-16v). I have attached a link to the module I am using and a picture of the diagram. I do want to use a PNP transistor as in the diagram also. Can anyone help guide me with components? Appreciate any help.
1674843018288.png1674842939024.png
Transistor 800V, 11A, 0.4Ω, price $6.44
https://www.digikey.com/en/products/detail/stmicroelectronics/STW11NM80/725404
 

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bradrs

Joined Jan 23, 2023
17
You use a flyback diode across the MOSFET similar to this circuit.
That IRF640 looks to have at least a 200V breakdown, which is better.

The waveforms Danko posted show what my question was. When you shut off the FET to fire the coil, the coil - wire tied to the FET climbs to 450V, the Vcoil in his diagram. If your FET Vbrdss is only 60V, then your FET will break down and absorb most of that spike.

The flyback diode across the FET would protect against a negative going voltage , and it seems like the diode in line between the coil and FET would only block in the same conditions, so it would be redundant to the flyback diode, but conduct whenever dwell occurs, so it looks like it functions mainly as a heater? I've never seen that in any single coil ignition circuits before. Maybe the dist. note means they are driving multiple coils in parallel, and that diode blocks them from interacting?
 

Reloadron

Joined Jan 15, 2015
7,580
The only reason I used the MOSFET I did was an example and because it is a logic level MOSFET and not knowing the planned gate voltage I went with logic level gate voltage.

That IRF640 looks to have at least a 200V breakdown, which is better.

The waveforms Danko posted show what my question was. When you shut off the FET to fire the coil, the coil - wire tied to the FET climbs to 450V, the Vcoil in his diagram. If your FET Vbrdss is only 60V, then your FET will break down and absorb most of that spike.

The flyback diode across the FET would protect against a negative going voltage , and it seems like the diode in line between the coil and FET would only block in the same conditions, so it would be redundant to the flyback diode, but conduct whenever dwell occurs, so it looks like it functions mainly as a heater? I've never seen that in any single coil ignition circuits before. Maybe the dist. note means they are driving multiple coils in parallel, and that diode blocks them from interacting?
What I posted came from here.

The purpose of the series 1N4005 diode is to allow the coil's primary to ring at a couple hundred volts when the MOSFET enters cutoff (or turns off), allowing time for a spark to form at the output. Otherwise only a very brief positive-going spike will result, as the internal body diode (and the other 1n4005) diode would clamp the ringing of the coil to -0.6V, greatly reducing overall performance. The other 1N4005 isn't necessary as the previously mentioned rectifier isolates negative-going voltages already. However the 1N4005 is a very poor choice. A modern high speed diode (intended for switch mode power supplies) or 200V+ schottky diode is preferable.
I should have included the link initially.

Ron
 
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