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Picture of Super Simple ignition coil drivers
danger-high-voltage-safety-sign.jpg
ignition coil circuit.gif

 
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Step 1: Lets start with the bacics

Picture of lets start with the bacics

OK, an ignition coil (or spark coil) is a type of induction coil similar to a Tesla coil . it's used in combustion engines. and produces up to 50,000 volts (a 2-4CM spark) at a lethal current of 25ma.

to power it, you need a square wave. you cant use standard AC because the coil WILL EXPLODE!

Step 2: How my schematic works.

Picture of how my schematic works.

This is how my schematic works: heres is a schematic that shows what the capacitor does. This the first schematic. It is a good driver for making big, hot sparks (not to be confused with arcs).

Step 3: My schematic (cheap and easy)

Picture of My schematic (cheap and easy)
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this is my schematic its easy, but it, with my power source, only makes about 20 KV (1 inch ark) at a low fixed freq. it's also noisy but still very cool. this makes VERY small streamers due to its frequency. and makes cool plasma globes out of light bulbs.

simple____ || ________________hard

$0.01__ || ___________________$50+

harmless shock ___ || __________________electrocution

Step 4: A super simple driver

this ridiculously simple driver with no doubt simple,and exceptionally cheap and can easily produce 40KV! there are a few disadvantages with it, its mains powered, making it dangerous, and the frequency is not adjustable.

simple_ || ___________________hard

$0.01_______ || ______________$50+

harmless shock _________________ || ____electrocution

(due to my laziness and super slow Internet, instead of pictures, here's another instructable showing how to build it. it will have the pictures and schematic in it)

Step 5: 555 timer driver

Picture of 555 timer driver

Another popular coil driver is the popular is this 555 timer driver.

it oscillates a transistor that drives the coil. its a little more costly and complicated but its overall relatively simple.

you can tune the output by the POTs. I haven't made the driver yet

simple____ || ________________hard

$0.01_____ || ________________$50+

harmless shock ____ || _________________electrocution

Step 6: Another 555 timer driver

Picture of another 555 timer driver

Here is another 555 timer driver. There are a few more components added and changed.
to me this is the most complicated circuitry I found.

simple_________________ | | ___hard

$0.01_____ || ________________$50+

harmless shock _______ || ______________electrocution

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beauchot7828 days ago

i built a tesla coil using a similar circuit. However i kept getting voltage spikes that would destroy the 555 timer chip after several minutes of operation. I put the 555 timer circuit in a metal container hoping this will fix the problem... ive tried adding capacitors at various location to try to absorb the voltage spikes, i also tried a few small coils to try and nullify the spikes with no success. The voltage spikes must be in the form of strong rf/emi signals so im hoping the metal box/faraday cage will protect the circuit. I built my tesla coil from a 9v battery to power the 555 timer circuit and a 6v battery to power the 6v ignition coil which drives the primary coil in the tesla coil. I have been getting about 2.5 inch sparks off the secondary.

MESHAAL1 month ago
Well the Rubbish controlled .
The pull down resistors works I used 4.7K , however I have feeling that the matrix keypads catching some also as the TX, RX pins of arduino is it right to connect pull down resistors to those pins .
P.S for the keypads I'm wiring directly to Arduino without resistors so I will try to add resistors between keypads and inputs pins .
-max- (author)  MESHAAL1 month ago
It is always good engineering practice to use pullup or pulldown resistors in any design, especially on floating pins for the very reason you experienced. Also, the same is true for unused op amps, comparators, and logic IC's where there is a unused or unwired 'unit' like for instance, you would true the inputs on a unused comparator together and wire that directly to ground if you were not using it.
-max- (author)  MESHAAL1 month ago
OK then. Did you know you can actually enable pullup (and I think pull-down) resistors in the arduino? the internal pullups are generally used for I2C interfaces.

Also, for the buttons to even work, they should already have pullups or pull downs on them, depending if the buttons are on the HIGH or LOW side.
MESHAAL1 month ago
Hello Max,

The transistors circuit working 100% , but still the problem with the EMI . If the arduino pin output not connected to the transistors base everything looks fine no EMF/EMI affect , but when the Arduino pin output is connected to the transistors circuit the things happened as the link below .
http://youtu.be/ROP9vYF0m9Y
-max- (author)  MESHAAL1 month ago
You're LCD is picking up interference from something, see those pins that are not connected? They are acting like antennas and feeding you're LCD controller rubbish signals. Rubbish in = rubbish out.

Other issues may include conducted interference, but I do not see that being possible if you used an optocoupler. Like I said, stick sensitive digital stuff into a metal case/box with a small cutout for the keyboard and LCD to be mounted. Also use pulldown resistors on all the unused pins on the LCD module so they do not pick up EM interference.

Honestly I think you are pretty brave to use a arduino to 'drive' the circuit at all, considering how often I pop 555 timers and ICs and transistors from a similar flyback driver.
MESHAAL1 month ago
I'm so confused now :(
-max- (author)  MESHAAL1 month ago

Sorry, yeah, here, let me draw a schematic instead, pics are worth 1000 words.

If you really want to enable/disable power to the 555, rather than using pin 4 connected directly to the arduino, this is how it would be done. Notice I did use a standard NPN transistor (Q1) on the HIGH side, but if you apply only 5V to base, then the 555 will only ever see 4.35V because of that 0.65V drop needed to turn on the transistor.

So if only we could figure out a way so that we can put 12V on the base of that transistor, so that way we can actually power the 555 with about 11.35V... Umm, I have an idea: Lets use a resistor, R1 that would normally pulls the base HIGH, to 12V, thus turning on Q1, but what about turning it off? Lets connect that optocoupler to the low side so that way when we turn it on via the LED built inside, it shorts out R1 to ground, and turns off Q1. Here it is:

Screenshot from 2015-05-21 17:51:32.png
MESHAAL -max-1 month ago
Max ,

This is awesome I will select the transistors and start testing it with with the cages .

Thank you for your valuables words and time.
MESHAAL1 month ago
I'm lost !.

If I supply the base of TIP transistor with 5 volt from arduino to turn on the 12v 555 ignitor circuit like power supply 12 ----> +ve of 555 circuit to Emmiter then collector ---> ground !. You mean it will not work ?
-max- (author)  MESHAAL1 month ago

If you use a TIP120 transistor with the collector connected to 12V, the base connected to a 5V arduino pin, then the voltage at the emitter will be 2.5V assuming 2.5V is what is needed to turn on the transistor, since it is a darlington pair. 2.5V is not enough to power the 555, you need at least 5V, preferably 7V or more.

MESHAAL1 month ago
I believe on using IRF 520 MOSFET as Arduino can drive it through pull down resistors . but how can i do the trick is it by connecting it to pin 4 of 555 timers or to switch the the main power of circuit ?
-max- (author)  MESHAAL1 month ago

Arduino should have push-pull outputs, I don't think you need any pull-down or pullup resistors on the gate. In fact, at least based on a quick LTspice simulation, it looks like you can connect pin 4 directly to the arduino. When pin 4 is not connected at all, the 555 will work as normal. Sometimes I forget to connect it entirely. When it is pulled low, the 555 stops and will reset when you apply 12V to it or 'release' it.

~~~~~~~~~~~~~~~~~~

Now if you really want to turn the whole circuit off completly, including the arduino, you are limited to using a mechanical switch, otherwise you will have to deal with some quiescent current, stand-by power draw.* When you use pin 4 to turn "off" the circuit, you are effectively stopping the 2N3055 from conducting any power, and the 555 and supporting circuitry draws negligible amounts of current.

(*There is a simple way to use a mosfet as a latch and have it so that effectively no power is drawn while in the OFF state, I will link in that video below here https://www.youtube.com/watch?v=Foc9R0dC2iI)

MESHAAL1 month ago
Thank you for the valuable information . what I should do if I want to interrupt the 555 timer ignition coil circuit ( instead of using switch ) by using Arduino as switch On/Off without any EMI interference through wires ? I'm thinking to use TIP120 , Collector connected to 12V source , Emitter connected to the power input of the 555 timer ignitor circuit and base to the digital output of arduino through resistor , but I'm not sure as you mention the maximum current of arduino pin is 10mA while the base current of the TIP 120 from datasheet is 120mA . I would like to use arduino as switch but the main problem here the EMI affecting the arduino and it's LCD. I built faraday cages for both Arduino and the coil circuit to control the EMF and it's work if the arduino is not connected through wires to the circuit . Once the connection made the arduino fail !. I was thinking to use IR transmitter from Arduino and the IR receiver on other side connected to the 555 timer circuit but it's fail as the transmitter IR of arduino is not switching fast on 10ms .
-max- (author)  MESHAAL1 month ago

Ahh, so now you are using the TIP120 as an Emitter-follower! (also called a common collector) These are really cool, and have some cool properties to them, but important ones to consider. The benefit of it is that config is that the current gain is really high, but the voltage gain is only 1 because the output "follows" the voltage at the base, minus ~2.5V which was needed to turn on the transistor to begin with. (it is a darlington pair, see the datasheet) If you put 1V more on the base, you get 1 volt more out the emitter, it's a 1:1 ratio.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Now one of the things that confused me in this video was him talking about output and input impedance (output and input Z). Think of it like this, impedance is like how much voltage vs current is needed. Something with high input impedance simply means that it is almost like an "open-circuit" and if with low input impedance, then that is more like a "short-circuit."

When it comes to output impedance, a low output impedance is like a grunty power supply that can really deliver the current without the voltage changing much. It is like a giant car battery, where the voltage will basicly be close to 14V regardless what you connect, even if it draws like 100 amps! A high impedance supply is one that is wimpy, and cannot keep the voltage the same. Actually, it does a much better job at keeping the current the same no matter what. If nothing is connected to a high Z supply, the voltage gets really big, but if something connected to it attempts to "load it down" then voltage sags... a LOT. The voltage will sag until the current is basicly the same as it was before. See how that works?

Here is the video where I learned how to really use transistors. It is a bit advanced and more suited towards RF and ham radio applications, but the same principles apply.

The reason it does this is because, well, lets make a idealized standard NPN transistor, one that's perfect, turns on 100% when there is the base of the transistor is 0.65V higher than the emitter (this important voltage difference is called Vbe), and the transistor turns off 100% when that Vbe is lower than 0.65V. So, let the collector go to the 12V PSU, and, say you apply 5V to that base from arduino. If there was a capacitor on the output of that emitter follower, going from ground to the emitter, then say that capacitor starts out at zero. Then the Vbe is a whopping 5V!!! That transistor is going to be turned ON really, really hard, and the capacitor will basically charge up (almost) infinitely fast, (only limited by ESR and parasitic effects, like resistance in wires.) and as that capacitor charges, the difference in Vbe gets smaller and smaller, once it reaches 5V-0.65V = 4.35V, the Vbe is exactly 0.65V, and the transistor is turning off-ish, and this ends up being a balancing action (negative feedback effectively) so the voltage stabilizes there. Pretty neat, huh?

-max- (author)  -max-1 month ago

Well anyway, what is the point of all that is to show you that the 555 is only going to ever see 5V - 2.5V(needed to turn on the TIP120), only 2.5V :( That is not enough to turn on the 555, I think it needs at least 6V to work, and the MOSFET needs at least 5V on the gate to turn on.

MESHAAL1 month ago
Or TIP120 connected to pin 4 of the 555 timer !
MESHAAL1 month ago
Sorry for low quality here is the circuit I'm trying to build to avoid the interference of EMI .
2015 01:52 am.jpg
-max- (author)  MESHAAL1 month ago
You might be able to get away with this, but I see a couple potential problems you should address. Since you are using a NPN BJT transistor, the 2N3055, you don't need the 10K pull-down resistor. That's only for FETs, where the gate "looks" like a small capacitor, no electrons flow through it. The resistor is necessary to bleed off the charge on the gate to ground when you want to turn the FET off Also, you can omit the zener diode, since the BJTs are current controlled devices, and since they "look" like diodes, In other words, once you pass 0.6V more than the voltage of the collector on the base of that 2N3055, it acts like a short-circuit and all the current flows through it, just like a regular diode. The current that flows through the base of the BJT is what turns on the transistor.

That 100 ohm resistor between the optocoupler and the 555 has me a bit worried too. Ideally you should look at the datasheet for the opto and see how much current is safe to go through the IR led in order to fully saturate the transistor at the other end. Then use ohm's law to calculate the current through the IR led taking into consideration the ~1.25V drop of the IR led, actually, you know what, lets go through it so you know how to do this the right way!

~~~~~~~~~~~~~~ IMPORTANT MATH TUTORIAL BELOW!!! :D ~~~~~~~~~~~~~~~

Based on THIS datasheet: http://www.vishay.com/docs/83660/moc8101.pdf to make sure you don't blow up your optocouplers, lets do a quick calculation to see if the 100 ohm resistor is acceptable. The 555 is powered with 12V, so we can assume the output of the 555 is 'close enough' to 12V, and the datasheet above tells me the absolute maximum current through the opto input is 60mA, and @ that current, about 1.25V will be dropped by the LED inside the optocoupler.

So we need to subtract 12V  -  1.25V = to get 10.75V which is what the 100 ohm resistor has to drop away. Ohm's law says that V / R = I so 10.75V / 100 ohms = 0.107A = 107mA!!! The first page on the absolute maximum ratings says that 60mA is the absolute maximum continuous current. Ok so now we know that might be a serious issue, lets figure out what resistor should be there:

To get the minimum value for the resistance, do the same calculation, but solve for resistance instead of current. Current should be at the very most 60mA, no higher. That goes into ohm's law, so does that 10.75V figure we calculated already. In this case, V / I = R. So 10.75V / 0.06A = 179.16... ohms. I would not use anything less than 200 ohms, and since the power supply might actually be as high as 16V or more, I would not use anything less than 250 ohms, preferably 300 ohms or more.
-max- (author)  -max-1 month ago

Similarly the opto at the arduino should have a current-limiting resistor like that, calculated for the 5V output, you also need to consider that the arduino chip itself cannot deliver (if I remember correctly) more than 10mA from any one pin, and not more than 40mA from any combination all most/all pins. so that needs to be considered. A wimpy 10mA may not be enough to drive that first opto, so you may need to use an additional MOSFET or BJT on the digital output to drive it.

One last note, I see the way you are interrupting the oscillation of the 555 timer is by effectively connecting and disconnecting the capacitor. That probably will not work too nicely. The problem is from my personal experiance working on a recent SSTC design, I found that when there is no capacitor, the output of the 555 will be a *really* high frequency, or just HIGH. If it is HIGH (12V) and that turns on the 2N3055, then that will cause a short circuit. It cannot stay on for a long time. With inductors, the longer they have a constant voltage across them, the more current will flow. If you turn that transistor fully on hard, and your power supply can deliver lots of power, the current will go up and up and up and up, until something gives way. Either the power supply, transistor, or coil will let out the magic smoke and might explode.

Instead, why not use the handy-dandy RESET pin (pin 4) on the 555? Connect that pin directly to an arduino digital GPIO pin? Set that pin HIGH when you want the circuit to work, and when you pull that RESET pin low, the 555 will not oscillate, and the output pin 3 will be off, or LOW. Then everything including the 2N3055 is turned off. Now of course in order for the arduino to drive that pin, electronics 101 (and honestly stuff I tend to forget when using the arduino) make sure the power supplies are commoned together, that all the grounds are the same, making sure the ground of the arduino is connected to the negative of the 12V supply.

Personally I think it would be a lot simpler to omit the 555 entirely, as it is all unnecessary complexity. The arduino (with a small amount of additional driving circuitry) can oscillate the ignition coil. however, I would then buy a separate atmel AVR, so I do not accidentally kill the $$$ arduino. the atmega328p is pretty cheap, this can be programed and dedicated for the purpose, so this way it can be a permanany programable project!

MESHAAL1 month ago
Thank you Max ,

What if I keep the 555 timer for oscillating function and connecting arduino to switch ON/OFF the 555 timer ?

I will draw the full circuit with arduino codes for evaluation .
MikaelV1 month ago
In "step 5" the ignition coil seems to be connected with plus to ground and vice versa. Anyone knows if that is correct or if it doesn't matter?
-max- (author)  MikaelV1 month ago

Yeah, you're right, it shouldn't matter, since it is driven effectively with AC anyway.

MESHAAL1 month ago
Hi Max,

I have built the 555 timer circuit and it's working 100% .

I'm trying to trigger the 555 timer by external trigger like arduino .
I
Simply Arduino will send a pulse to the 555 timer to trigger the spark e.g in arduino I'm able to enter the ON time and the OFF time with cycle mode . The issue I'm facing is the EMF which it's generated from the spark , I keep getting abnormal character on Arduino LCD and I have to reset it every time .

I'm thinking to use optocoupler to isolate arduino from the 555 timer circuit by connecting pin 2&6 to optocoupler as attached drawing .
If you have any idea to control the EMF please let me know .
-max- (author)  MESHAAL1 month ago

There are 2 ways (that I know of) of how strong EMI (ElectroMagnetic interference) can adversely affect the sensitive digital electronics. One way is galvanically conducted (this is what you are thinking of, through wires and such with voltage and current transients) and the other is through electric and magnetic fields. (EM fields)

You are thinking the right way with using a optocoupler, so that is not a bad idea. You can actually omit the 555 entirely and use the optocoupler to drive the MOSFET directly, and the oscillating could come from the arduino. You can set up the output of the pin to output a tone, there should be a arduino library for that. Anyways, that would drive the LED in the optocoupler, which the phototransistor at the other end pick up on, and that can drive the gate of the MOSFET.

http://www.talkingelectronics.com/ChipDataEbook-1d...

The schematic above may be what you want to build up. You can see that there is a very basic 15V linear shunt regulator made with the 15V zener diode and resistor above it, and that is connected to the collector of the transistor of the optocoupler, which is being used as an emitter-follower which drives the gate of the FET. There is also a pull-down resistor so when the transistor is not turned on, the gate of the FET can be discharged so that it turns off quickly. Instead of a motor, you would use your ignition coil, or whatever the other schematics call for. A small 0.1uF film capacitor may be in place of that back-EMF protection diode.

~~~~~~~~~~~~~~~~~~~~~~

Ok so that takes care of avoiding all possible conducted interference, but I bet you will find that is not the issue. (otherwise it is likely you have destroyed the arduino, or at least that specific output.) The electric field interference (the same type of EMI that make the flourescent lights glow near tesla coils) can be easily stopped with a faraday cage, so shield your electronics. Put them inside a computer ATX power supply case, or a altoids tin, a tin can, or something similar. a closed metal box will greatly reduce interference to whatever is inside.

~~~~~~~~~~~~~~~~~~~~~~~~

magnetic interference is considerably harder to deal with, but that is not likely to be an issue for you, esp. since the ignition coil is already well-shielded and has a closed iron core which keeps most of the magnetic flux internal. The only thing I can thing of that will solve this is thick iron or "mu metal." mu metal is very expensive and is a proprietary nickel–iron alloy, made up of 77% nickel, 16% iron, 5% copper and 2% chromium or molybdenum, and probably some unobtainium. It can however be found in the back of old CRT TV's where electronics need to be well-shielded from the incredibly strong electromagnets that sweep the electron beam inside the HV tube.

~~~~~~~~~~~~~~~~~~

Anyways, that was a mouthful, I hope that clears things up.

MESHAAL1 month ago
Drawing .
2015 04:15 pm.jpg
MESHAAL1 month ago
Ders,

Any idea to how I can connect optocoupler to pin 2 of the 555 timer to trigger it by external trigger ?
-max- (author)  MESHAAL1 month ago

Not exactly sure what you mean or want. The 555 circuit using the 555 in an astable configuration for oscillation, and there is no optocoupler in the circuits.

apillai56 months ago

Hey Max , Do you remember me ? . Anyways I need your help . , i made this circuit and i have gotta problem , The 100ohm Resistor is getting Too hot and the 555 Timer got blown The Transistor is also getting too hot . The circuit works when i pulse the Dc , And I have not connected the capacitor as i do not know the value of the capacitor . SO PLEASE HELP ME MAXX

F4YXVBHGC1KVETG.LARGE.gif20141212_133009.jpg
-max- (author)  apillai56 months ago

Pin 3 output is limited to I think about 200mA sink and drain. With 100 ohms, that means there has to be a potential difference of 20V across it. How much voltage are you feeding this circuit? The ne555 will not tolerate anything more than 16V, so do not feed it more than 12V w/o a voltage regulator.

To me that appears to be a 1/4 watt resistor, so you cannot dissipate more than 1.4W though it. Knowing that the 555 is capable of supplying enough current. 106mA @ 12V-1.4V(transistor's saturation voltage), totaling over 1.12W will completely fry that sucker, and since you only need a few mA's to saturate the transistor, you will need to choose a different, higher value resistor. Try a 220 ohm, or 470 ohm resistor. Keep incrementing up or down to find the best value.

Also, I did not build this circuit, I just put it all the circuits I found online into one place! Sorry if I can't help you more than that.

AdithyaP -max-6 months ago

I have mentioned in the photo of the circuit , 12V 2A wall adapter

-max- (author)  AdithyaP6 months ago

OK then, I can now see many, many problems. First and most importantly, do *not* omit the capacitor, it is necessary for the 555 to oscillate properly. Otherwise the stray capacitance between the pins will result in a very weak and unstable UHF oscillator that cannot drive the transistor or the coil. The value of it I believe is 0.1uF, but some experimentation will be needed to choose the exact value. (the output freq. should be between 40Hz-400Hz.) A "104" numbered ceramic capacitor should do the trick.

12V @ 2A is most likely not enough to get good performance. Once you get the circuit to function, you will probably be disappointed with the output. As the schematic you have shown calls for at least a 6A power supply. You can probably use an SLA battery for power. 12V high amperage power supplies are also really cheap, I modded an old Xbox power supply so that it can output 12V @ 12.6A. (Before the mod, even small over current transients would cause the thing to go into a fail-safe mode and shut down until power is removed. There was a custom chip that was responsible for that protection, and I simply shorted the optocoupler to the +5V rail though a small resistor, effectively bypassing the whole protection IC. Now there is no current limit or short-circuit protection)

Once you get the beefy power supply sorted, mount the transistor to a heat-sink or else it will overheat. TO-3 package style transistors are becoming more rare these days, so that is why an MJE3055 or TIP3055 may be a preferred choice. heat sinks for these are more common and readily available. Then if you still have issues with the 100ohm resistor, either try a higher value, or get a 3W 100 ohm resistor. Hope this helps.

AdithyaP -max-6 months ago

I am going to buy a 12V high amp adapter and try your recommendation :D
and i do have the heat-sink

-max- (author)  apillai56 months ago

If you still have problems, and you think you are killing the 3055, try a TVS diode across the collector and base that is reverse-biased (backwards so it does not normally conduct), and that it has a breakdown voltage of around 60-70V. A few zener diodes may also help, make sure they are beefy or paralleled up to handle the EMF transients well.

-max- (author)  apillai56 months ago

Your transistor should be mounted on a heatsink. This circuit is not the most efficient and as the transistor warms up, the worse it will perform and the less efficient it will become. That leads to thermal runaway (as it heats up, it makes more heats, causing it to heat up faster). The NE555 is not really the best chip to use with these types of circuits because it can be killed with strong EMF. Make sure use a separate power supply for it (from the main ignition coil power supply) or some beefy LC filtering and voltage regulators (with current limiting).

dillonxti1 year ago
relay circuit really works on msd blaster 2 coils
-max- (author)  dillonxti1 year ago
Great! Add some images, I'd love to see 'em!

here is my circuit

temp_715383054.jpgtemp_-916830694.jpgtemp_-384727899.jpgtemp_-825335432.jpgtemp_930114503.jpgtemp_1341175757.jpgtemp_2108787039.jpgtemp_150704653.jpg
deej3972 years ago
Hey what type of power would you use for your step 5 schematic? Right now I'm trying to use a 12v lantern battery I got from radio shack but its not working. Also I'm on a breadboard just for testing purposes. I thought this could be done with 9v batteries so you'd think a 12v lantern battery would work but I'm having no such luck. Thank you

it is a 6v lantern battery not a 12v

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