Ignition circuit help

[stevehuckss396]

I was hoping one of you electronics Guru's might be able to analize this circuit and tell me if it can be triggered by a hall sensor. The circuit was designed to upgrade using existing points. The ignition comes in kit form for 22 bucks + postage. I was hoping I could use it with a hall effect on my next engine because the modern CDI units wont do what I want/need them to do.
If it cant be used with a hall sensor, can it be modified to work with it? I have a round PCB about 3 inches in diameter to build the circuit.
Thanks in advance!!

 

[Herbiev]

Yes it can. Hall effect is just a switch operated by a magnet. Just connect sensor in series to input and it should work fine.

 

[MuellerNick]

Hall effect is just a switch operated by a magnet.

A switch operated by a magnet would be a reed switch.
Hall effect

Nick

 

[Graham]

Hi Nick,
A reed switch is a mechanical device ( too slow for an ignition system) hall effect is solid state and so triggers much faster.
I tried to use a reed switch some time ago and couldn't get it to work, it might be OK on a very slow running engine though.
Graham

 

[MuellerNick]

A reed switch is a mechanical device

We both know, Herbie didn't.
Recently, I looked how fast reed switches can be, and I was amazed. Up to 300 Hz!
That would be 18000 RPM. Certainly needs some tinkering, reading the data sheet and picking the right one.


Nick

 

[Graham]

Hi steamer,
Have a look at 5 bears ignition systems, there is a brilliant circuit there ( the last one on the list I think) it uses a darlington pair transistor.
Only one transistor and one resistor very simple to make and a very hot spark. I have this running with a hall effect on a couple of single cylinders one 4 stroke and one 2 stroke.

 

[Graham]

Nick, I stand corrected.

 

[stevehuckss396]

Thanks everyone! I will look at the 5 bears site pronto!

 

[jasonh]

The essential part of a hall effect device is a piece of semiconductor that has a current flowing through it. In the presence of a magnetic field charge separation within the semiconductor leads to a voltage across the device in a direction transverse to the current. Manufacturers generally integrate supporting circuitry around the hall effect device to make it easier to use - typically more switch like.

Could you use a hall sensor in that circuit in the place of simple points? If the hall sensor in question has good switch-like characteristics it might work. ie- high/low, reasonable forward current. More typically you'll see a hall sensor connected to the base of a transistor or an op-amp input.

http://www.electronics-tutorials.ws/electromagnetism/hall-effect.html

 

[Herbiev]

Herbie did know. Perhaps I should have said solid state switch operated by a magnetic field instead of switch. I am sure most members with a basic knowledge of these devices would understand what I meant. Having worked as a telecommunications technician for over 40 years I am pretty familiar with all switching devices. The question was could it operate the above circuit? I believe I answered that Nick !!
Steamer you will find when you purchase one of these devices they usually come equipped with a small cylindrical permanent magnet with poles clearly marked

 

[stevehuckss396]

Well! My ignition circuit is a failure or should i say my coil is a failure. I am getting a very weak spark if any. I am thinking the coil might not be designed for this type of circuit. I wired the coil to ground and just shorted and unshorted the coil wire and I get slim to none. I tried a 66 caddy coil and got spark.

Do I need a CDI ahead of the coil. Could the primary winding need more than 12V to get a good spark. It seams like I have the same problem as Keith5700 and his V8. I think we might have used incompatable coils.

 

[canadianhorsepower]

Steve , you should try it with a capacitor between the coil could be that your pulse is so short
or week that your coil is not totaly loaded

 

[canadianhorsepower]

Steve forgot to ask what do you have on pin 1,2,3,4 if it's what I think you can't drive this with a hall sensor

 

[Lakc]

Whats the resistance of your coil primary and secondary winding, check the caddy coil too.

 

[canadianhorsepower]

Whats the resistance of your coil primary and secondary winding, check the caddy coil too.

good question, this was my next one I whent in my shop today and tried
a few thing. I think that to many issue is causing many heart breaking not
starting engines. I build the (5bears ign # tim6 with the NTE2329 I had in stock) with an hall effect sensor, output fine on the scope. Then just to put some spice on french fries instead of driving a coil I whent for a DC motor
with permanent magnet, close enought to a coil. I could go up to 100khz
before I had any bad fluctuation on the scope, change resistor value on base
and back solid to105K after that alot of noise and that was it. I must tell you that the motor got EXTEMELY HOT:fan::fan:
This diagram works for sure.
so if we go around all the math your primary cant be more then 30 ohms
hope it help

 

[Lakc]

Im thinking those snowmobile coils might be high primary resistance magneto coils. In which case I gotta whip up another test CDI on a round circuit board...

 

[dsage]

The circuit you posted is a poor variation of the "old school" TIM circuit. A hall sensor in theory will activate it but the resistor values on the front end are pretty low value and depending on the sensor it might not be able to drive the circuit and/or may damage the sensor. The problem with all of the original TIM circuits is the output transistor breakdown voltage. In order for a coil to work properly you must not supress the kickback voltage generate on the primary side of the coil when the "points" open. When you use conventional points there is no problem since the points gap is quite large.
In the case of the TIM circuit the transistor breakdown voltage is perhaps (unchecked for the particular transistor) 150volts at most. This will limit the seconday Hi voltage to 150v x the turns ratio of the coil. Typical turns ratios are about 100:1 therefore the secondary will only get to 15kv. That's probably more than enough for a model engine but you can do better.

Try my circuit below. It has the following improvements:
1. The front end is designed for a Hall sensor.
2. The first stage does not sit around consuming a lot of power when the engine is not running. The circuit you presented consumes considerable power just sitting there doing nothing.
3. A big problem with all of the TIM circuits was that it was possible for the engine to stop with the ignition activated which could (usually did) burn out the coil and or transistor or both. This circuit will not do that.
4. Most important is, this circuit uses a proper IGBT transistor to drive the coil. One that is made specifically for this purpose for automotive ignition systems. It has a very high breakdown voltage.
5. A little extra benefit is the LED which blinks when the Hall sensor is activated so you can tell if there is activity.
6. The input circuit can be run on the same 12v as the rest of the circuit but need not be. Just be sure the ground is common to both supplies.
7. And the best part - the IGBT is a logic level input device so, if you are so inclined you can elminate the front end altogether and drive the IGBT base with a microprocessor or logic chips.

Note that the symbol for the IGBT transistor is not precise. It's drawn like it is to make if familiar to the original circuit. The IGBT is a TO220 device so you'll need to consult the spec sheet to get lead orientation.

With a little ingenuity you should be able to use your existing circuit board by leaving out components and perhaps cutting traces and adding jumpers.


[EDIT Feb. 22 2013]
Updated drawing. I had the wrong part number variant for the IGBT transistor. Sorry. All is correct now.

Sage

 

[jgedde]

The circuit you posted is a poor variation of the "old school" TIM circuit. A hall sensor in theory will activate it but the resistor values on the front end are pretty low value and depending on the sensor it might not be able to drive the circuit and/or may damage the sensor. The problem with all of the original TIM circuits is the output transistor breakdown voltage. In order for a coil to work properly you must not supress the kickback voltage generate on the primary side of the coil when the "points" open. When you use conventional points there is no problem since the points gap is quite large.
In the case of the TIM circuit the transistor breakdown voltage is perhaps (unchecked for the particular transistor) 150volts at most. This will limit the seconday Hi voltage to 150v x the turns ratio of the coil. Typical turns ratios are about 100:1 therefore the secondary will only get to 15kv. That's probably more than enough for a model engine but you can do better.

Try my circuit below. It has the following improvements:
1. The front end is designed for a Hall sensor.
2. The first stage does not sit around consuming a lot of power when the engine is not running. The circuit you presented consumes considerable power just sitting there doing nothing.
3. A big problem with all of the TIM circuits was that it was possible for the engine to stop with the ignition activated which could (usually did) burn out the coil and or transistor or both. This circuit will not do that.
4. Most important is, this circuit uses a proper IGBT transistor to drive the coil. One that is made specifically for this purpose for automotive ignition systems. It has a very high breakdown voltage.
5. A little extra benefit is the LED which blinks when the Hall sensor is activated so you can tell if there is activity.
6. The input circuit can be run on the same 12v as the rest of the circuit but need not be. Just be sure the ground is common to both supplies.

Note that the symbol for the IGBT transistor is not correct but it's displayed as it is to make if familiar to the original circuit. The IGBT is a TO220 device so you'll need to figure out the proper lead orientation.

With a little ingenuity you should be able to use your existing circuit board by leaving out components and perhaps cutting traces and adding jumpers.

Sage

A reasonable circuit. But, your coil is wired "upside down." The return side of the HV should NOT be connected to the collector of the transistor...

I like the way you've AC coupled the Hall sensor so the battery doesn't get drianed or the coil burned out if the crankshaft is left in the triggered position.

John

 

[stevehuckss396]

Whats the resistance of your coil primary and secondary winding, check the caddy coil too.

The primary was 0.6 ohms. Didn't check the secondary. I will check all of the coils and post back tomorrow.

 

[stevehuckss396]

Steve forgot to ask what do you have on pin 1,2,3,4 if it's what I think you can't drive this with a hall sensor

I don't have pins 1-4, I only have a black and red wire on the primary side.