Download Ignition coil driver

Ignition coil driver
Here is a very simple circuit that will provide high voltage (15-40kV) sparks using a
common ignition coil. The input is 12VDC at around 5 to 6 amps. Mine produces sparks
that are about 3/4" to 1" in length. A 2N3055 NPN power transistor is pulsed with a
square wave signal that comes from the 555 timer IC. The frequency of the pulses
depends on the resistors between pins 7 and 8 and between pins 7 and 6. The pulse is also
dependent on the capacitor. You can experiment with these values. Try inserting a
smaller capacitor to raise the frequency. At different frequencies the sparks will change
certain characteristics. At a high frequency the sparks will get fatter but shorter in length.
At lower frequencies the spark maybe longer but thinner. I assembled my project on a
solderless breadboard. You can use whatever you like. The capacitor should be a
tantalum or mylar type, but this is not absolutely necessary. A ceramic type should work
fine just as long as the temperature is not too high around it.
If you mount this in a project box, I would suggest that you make the potentiometers
external so if you decide to change coils you can easily adjust for the new coil. The arc
should emit a mid-range audio frequency (determined by the resistors and capacitor)
which is perfectly normal. This circuit has also been tested with flyback transformers
wound with a 10-12 turn primary and it works very well. It is a very universal circuit, and
can even drive standard iron-core transformers (12Vsec, 120/220Vpri) to charge
capacitors for xenon flash applications.
This circuit works great for a Jacob's ladder and triggering large xenon flash tubes. You
can even build a miniature Tesla coil from this. If the ignition coil only gives a thin and
threadlike sparks at first then adjust the potentiometers for a thick, firery orange arc. If
you still cannot get a decent arc, make sure your power supply has a high enough current
capability, or just use a car/motorcycle battery.
If you need more voltage output use two coils with their primaries connected in parallel.
Make sure the symbols (+ and -) oppose eachother on the coils though. Also, if you are
using the original spark plug wires these will prevent arcs and make the sparks very
weak. This is because these cables have a high resistance. They aren't copper, rather they
are carbon strands. They make a good high voltage resistor, but will definetly weaken the
ignition coil's output. I just use a standard piece of copper wire attached to the original
plug that went into the high voltage terminal of the ignition coil.
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Here is probably the best ignition coil driver circuit that I have seen. As far as I know it
was designed by Jochen Kronjaeger. You can find the original at Jochen's High Voltage
Page This circuit is designed to run from 230V, but I have came up with a circuit that will
run from 120V about just as well. You will need to find two ignition coils (preferably of
the same type), a 100uF with at least a 200VDC rating, a full-wave bridge rectifer with a
rating of about 5A at 200VDC. A large power resistor with at about 150-200ohms
resistance and a power capability of at least 100W, or you can use an aquarium
immersion heater. The next two things are optional, but they will make the project a lot
more interesting. You might want to get about three 6A 200VDC SCRs. You can get
these from Radio Shack. You might also want a simple square wave pulse generator. This
can be just a simple 555 timer circuit. Make sure you can vary the frequency on it.
Ok, here is a simple schematic showing my project:
This circuit is fairly easy to build. If you can't get an SCR, you may also use a TRIAC as
a substitute. If you can't get either then you can use a relay, switch, or just two pieces of
wire to trigger it. The contacts will probably be burned out soon though. The resistor or
heater is used so that the power doesn't need to be cut when you discharge the capacitor.
It limits the current to a safe value when discharging the capacitor. If you choose not to
use the current limiter, the power will have to be unplugged every time you discharge the
capacitor. If you cannot find a heater or power resistor you can also use a common
household lightbulb. This will also give you a visual indication when the capacitor is
charged. The bulb will go out when the capacitor is fully charged.
See Automobiles for ignition coils.
This is a very simple ignition coil driver circuit which can probably be built with stuff
from your junk box. It is very easy to construct, and can be done in a few mintues. You
need an ignition coil, a household lamp dimmer, and 1uF capacitor (600V for added
safety).
This circuit should be good for about 10-20kV, depending on the ignition coil you use.
Here is another very easy ignition coil circuit which runs from line voltage as well. It
uses a TRIAC and a DIAC and can produce extremely high voltages (up to 40kV) from
120VAC input.
Higher voltages can be obtained by increasing the .1uF capacitor to .3uF or .4uF. Make
sure the capacitor is below 1uF, if you do not the coil will probably be ruined.
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