AC driven ignition coil

[J_Nichols]

Hi folks,
I was working with an ignition coil with DC electricity and changing the frequency of the pulsed DC to produce a big or a small spark at the output from the ignition coil.

Now, I have to test the same car ignition coil (rated at 12 Volts) with alternating current. My question is if I can use 12 VAC to input the coil as shown in the below schematic.
a) It will produce a spark using AC?
b) Do I need to add some electronic component to prevent damage to any piece? I don't know if I could produce a short circuit or to damage the transformer from the ignition coil's back emf, etc...

**broken link removed**

Uploaded with ImageShack.us

 

[Reloadron]

Something I have done over the years is using a coil like the one pictured I have driven it using a simple cheap lamp dimmer, the triac type. I have seen them in home improvement stores for less than $6.00 USD.

Ron

 

[J_Nichols]

I purchased some time ago a power adjustable thyristor transform.
**broken link removed**

Do you consider that I have to add some kind of protection to prevent damage in the circuit from the back emf of the primary ignition coil?

 

[Reloadron]

When pulsing a coil with DC a flyback diode can be added for the back EMF. I wouldn't worry about it with AC. I never had a problem.

Ron

 

[DerStrom8]

I don't know, I wouldn't trust connecting it directly to an AC source. I would use the lamp dimmer, like Ron suggested.

**broken link removed**

I've actually used that circuit a lot, and it works great. I bought a lamp dimmer for $4 at Walmart and pulled a capacitor off of an old circuit board. Just make sure that the cap isn't polarized, or it could explode. The voltage rating of the cap also needs to be well above the mains voltage (at least twice as much). With this circuit, you can run it directly off 120/240vac mains current and you get very nice arcs out of it.

But I must stress, as with all high-voltage projects, that you MUST be extremely cautious and careful when fooling around with this. Even if the output of the coil isn't enough to kill you, a high voltage arc through you to the mains power cord will create a low-resistance circuit to your household current. This IS enough to kill. Please take all necessary precautions to keep you and others safe.

Best regards,
Der Strom

 

[J_Nichols]

What would be the capacitance you suggest for the cap?
A doubt that still remains is about the power adjustable thyristor transform. It would be ok or a dimmer could be a better choice?

 

[DerStrom8]

What would be the capacitance you suggest for the cap?
A doubt that still remains is about the power adjustable thyristor transform. It would be ok or a dimmer could be a better choice?

The capacitor limits the current allowed through the circuit. The higher the capacitance, the more current flows, and the hotter the arcs are. However, a higher current causes the coil to heat up, too. You need to find the perfect balance. You can get some nice blue sparks with a .5uF cap, or you can get some nice hot arcs with a 10uF cap. I've run my coil with a 14uF capacitor and it worked great. I got nice fiery arcs and the coil did not get very warm. Depending on the insulation of your coil, you could probably go up to 25-30uF safely, but check the coil every now and then to make sure it isn't too hot. If it doesn't get hot at 30uF, you may experiment a bit (cautiously, of course) with higher capacitance. Work your way up, checking the temperature of the coil every now and then, until you get the output you desire.

Regards,
Der Strom

 

[J_Nichols]

Today is saturday and the shops of electronics are closed. So I've used a 16V 1Ampere 50Hz AC transformer I had at home as the input to the ignition coil. In the high voltage output I cannot get a small spark when I put the output wire near to a metallic object. The only thing I see is when I introduce a screwdriver to the high voltage output of the ignition coil, there is an attraction like in a magnet (well, the secondary coil has a core of iron and it's an electromagnet).
When I used 30Khz DC 12V 1Ampere, I didn't get that effect (magnetic attraction) but I got the sparking.

I've thought that maybe the power factor is zero while using AC because the coil is using only reactive power, and nothing happens in the output. But Reloadron and Der Strom said that the ignition coil works using AC. So I don't know what is happening.

 

[shortbus=]

You won't get a sparking like a Tesla coil. The spark from an ignition coil will only jump to a surface that is in contact(part of) the coil case or negative of the primary.

 

[DerStrom8]

But Reloadron and Der Strom said that the ignition coil works using AC. So I don't know what is happening.

I didn't think it would work connected directly to an AC source. That was the purpose of the dimmer switch in the circuit I posted. The dimmer "chops up" the sine wave into different wave shapes, and the one you're looking for (which is down on the lower end of the dimmer range) is the square wave. It won't work connected straight to AC.

Der Strom

 

[J_Nichols]

You won't get a sparking like a Tesla coil. The spark from an ignition coil will only jump to a surface that is in contact(part of) the coil case or negative of the primary.

I can discuss that for my own experience. When I use 12V 1Ampere Pulsed DC, the spark jumps to an object independent to the coil. I connect in the high voltage output a wire and using that single wire I can make some sparks in a metallic object or also in myself. No negative connection necessary.

**broken link removed**

I didn't think it would work connected directly to an AC source. That was the purpose of the dimmer switch in the circuit I posted. The dimmer "chops up" the sine wave into different wave shapes, and the one you're looking for (which is down on the lower end of the dimmer range) is the square wave. It won't work connected straight to AC.

Der Strom

I better understand it now. My purpouse was to put AC directly to the ignition coil. Not to use AC as the source and then a device to finally input square waves into the coil.
If I use pulsed AC it would work? When you disconnect the power source from the coil, as happens when using pulsed DC, the magnetic field of the coil collapses and it probarly would produce the same effect as the pulsed DC.
I've just tested right now to connect 12 VDC without pulsing it and it produces the same effect as when I connect AC. It creates an attracting magnetic field in the high voltage output. So I think pulsing AC could mimic the same effect as pulsing DC. Right?

 

[DerStrom8]

I can discuss that for my own experience. When I use 12V 1Ampere Pulsed DC, the spark jumps to an object independent to the coil. I connect in the high voltage output a wire and using that single wire I can make some sparks in a metallic object or also in myself. No negative connection necessary.

I can vouch for that. The spark is much less energetic than one to ground, but the spark still occurs.

**broken link removed**





I better understand it now. My purpouse was to put AC directly to the ignition coil. Not to use AC as the source and then a device to finally input square waves into the coil.
If I use pulsed AC it would work? When you disconnect the power source from the coil, as happens when using pulsed DC, the magnetic field of the coil collapses and it probarly would produce the same effect as the pulsed DC.
I've just tested right now to connect 12 VDC without pulsing it and it produces the same effect as when I connect AC. It creates an attracting magnetic field in the high voltage output. So I think pulsing AC could mimic the same effect as pulsing DC. Right?

I think that's pretty much what the dimmer switch does--it's an easy way of pulsing the AC. But, may I ask why you want to use AC when your DC source works fine? What's the point? If one works well, why do you need another method?

 

[J_Nichols]

A friend told me that if the power factor is zero then the energy consumed by the ignition coil is almost nothing (all is reactive power, to energize the coil and it doesn't perform work). So I could increase the battery life more time and this doesn't happens if I use DC. I'm helping to a friend to make a small motor to put in a remote controlled car and the battery's charge is an important factor to look at.

 

[DerStrom8]

A friend told me that if the power factor is zero then the energy consumed by the ignition coil is almost nothing (all is reactive power, to energize the coil and it doesn't perform work). So I could increase the battery life more time and this doesn't happens if I use DC. I'm helping to a friend to make a small motor to put in a remote controlled car and the battery's charge is an important factor to look at.

So what is the ignition coil for? Or is this a gas-powered remote controlled car?
The coil will be kind of useless if the energy consumed by it is low. Low energy in = low energy out, which won't work very well at all.

 

[J_Nichols]

The ignition coil is for use in a remote controlled combustion motor.
The idea comes from this hyphotesis. The ignition coil helps to produce a spark to ignite the gasoline mix in the motor and it causes the explosion. For the ignition coil to work, it only needs to produce a magnetic field and when we disconnect the power source from the coil, a spark is created. If only magnetizing energy is necessary to produce the spark (reactive power), then the power factor will be zero because all the energy is reactive.

When we use DC, energy is consumed. But when using AC and only 100% reactive power (power factor = 0) then no wattage is used since Voltage x Intensity x Power Factor (0) = 0 Watts. But the coil can produce a magnetic field that doesn't produces work, and the energy of the spark cannot produce work. So watts = 0 and we can save energy from the ignition system of the rc car. Of course, I would need a transformer to produce AC and in the process (from DC to AC) I can loose some watts due to heat in the transformer and the miliwatts that the pulsing circuit uses, but forget the energy consumed in this last part.
Correct me.

 

[DerStrom8]

The ignition coil is for use in a remote controlled combustion motor.
The idea comes from this hyphotesis. The ignition coil helps to produce a spark to ignite the gasoline mix in the motor and it causes the explosion. For the ignition coil to work, it only needs to produce a magnetic field and when we disconnect the power source from the coil, a spark is created. If only magnetizing energy is necessary to produce the spark (reactive power), then the power factor will be zero because all the energy is reactive.

When we use DC, energy is consumed. But when using AC and only 100% reactive power (power factor = 0) then no wattage is used since Voltage x Intensity x Power Factor (0) = 0 Watts. But the coil can produce a magnetic field that doesn't produces work, and the energy of the spark cannot produce work. So watts = 0 and we can save energy from the ignition system of the rc car. Of course, I would need a transformer to produce AC and in the process (from DC to AC) I can loose some watts due to heat in the transformer and the miliwatts that the pulsing circuit uses, but forget the energy consumed in this last part.
Correct me.

Yes, I understand the theory of how an ignition coil works.

Another thing to consider is, as you mentioned, you'll need a DC-AC transformer. You'll need to pulse the DC into the transformer, so you'd be better off simply pulsing current into the ignition coil. You may also be able to work out some sort of alternator system in the RC car, just like in a real one. Just something else to consider

Der Strom

 

[J_Nichols]

Thank you very much for the recommendation, I will comment it to my friend and we will examine the possibility.

Just a question that is still pending. When I connect AC directly to the ignition coil. What is the power factor? Zero? I think it's zero since only magnetizing current (reactive power) is used, because the only necessary thing is to build a magnetic field in the coils. Right?

 

[DerStrom8]

I'm not sure about the power factor, but I can tell you for sure why it doesn't spark off of just AC. The ignition coil relies on a sudden collapse of the electromagnetic field to create a spark. When you connect it to AC, however, it creates a sine wave in the coil. The voltage increases and decreases, rather than just turning on and off. This doesn't create a sudden drop in voltage; it's more of a (relatively) slowly decreasing voltage. That is why the coil will not arc with a simple AC sine wave.

Der Strom

 

[J_Nichols]

Thanks for all, I will tell you more when I make some test.

 

[em2006]

One of my solutions (110VAC):
**broken link removed**

and 220VAC:
**broken link removed**