Using 12VDC and a car coil to create an ignitor
Using 12VDC and a car coil to create an ignitor
(OP)
I am trying to put together a really simple ignition system for our indirect heaters that are in areas where no electricity is availible. The goal here is to use about a 7Ah 12DVC battery, a coil off a car, a push button and an ignitor rod. The problem I am running into is how to get the 12VDC to oscillate for the coil like an old points distributor does for a car. Anyhow I think that is the problem. I would really like to find a "black box" that does this i.e. wire the 12VDC to it with the push button interrupting the negative leg and from the "black box" continue the 12VDC to the coil. Then again I could be approaching this completely wrong. Any suggestions?
Darren
Darren





RE: Using 12VDC and a car coil to create an ignitor
you don't have to make an AC voltage. What you need to do is simply disconnect the current to the primary of that coil you've got. What happens is an impulse voltage (due to a rapid change in current, i.e. v=L di/dt) induced into the primary and luckilly it osscillates itself for some miliseconds, that will be transmitted to the secondary as an impulse with a peak of N times more (N=N2/N1 and depends on your coil specification). Distributor in a car just DISTRIBUTES this secondary voltage to different plugs on different cylinders. So if you have a single-cylinder car you don't need any distributor and you can still have your ignition system for that imaginary car.
If you'd like to find out more about signal shapes of secondary and primary sides you can search "ignition signal shape" in "google IMAGES".
If you share what you know, you'll never forget it.
Cheers
Zimbali
RE: Using 12VDC and a car coil to create an ignitor
Typically, from a 12 volt battery yous should get between 30KVDC to 90KVDC.
I still use one of these setups for my experiments. The only difference is that the primary is driven from a bistable, monostable or astable firing circuit as the experiment requires. Have fun!
RE: Using 12VDC and a car coil to create an ignitor
The "circuit" will be dead until an operator comes up to the heater to lite the pilot and hopefully will do so by simply pushing a momentary push button. The coil should generate a secondary voltage as long as the operator pushes the momentary push button. Sometimes you need just a second of spark and other times a few seconds to light the pilot. Once the pilot is lite then a manual valve is opened to light the main burner. Really simple little 1.0MM BTU indirect heater.
Now that I have written this I believe what I need to know is how a coil actually works. I have always just taken them for granted, I know it is sad but true. I will do a search like Zimbali suggested and see if I can learn something today.
Thanks for the information and help.
Darren
RE: Using 12VDC and a car coil to create an ignitor
Would a piezoelectric striker like a “Lightning Bug” do?
Hypothetically, a mechanical oscillator/chopper/buzzer from a small DC relay with a series NC contact would be guaranteed not Factory Mutual or American Gas Association approved.
RE: Using 12VDC and a car coil to create an ignitor
darren
RE: Using 12VDC and a car coil to create an ignitor
The little heater 'igniters' you're thinking of are piezo-electric and produce a high voltage when mechanically compressed.
RE: Using 12VDC and a car coil to create an ignitor
You seem to be on the same page with me. I understand a battery will be needed. The system will work off of a 12VDC 7Ah battery. I just mocked the system up and got it to spark for everytime I depressed the push button. So for multiple sparks I had to manually cycle the pushbutton. What I need is something that will continue to spark while the push button is held in.
Here is what I thought might work but did not. The push button is placed between the NEG lead on the coil and the NEG of the battery. I thought that if I put a relay between the push button and the NEG of the battery I could get the relay to chatter and cause the multiple spark effect.
Here is how I wired it and the result. The NEG of the battery was wired to one side of the coil on the relay while the other side of the coil was wired to one leg of the N.C. contact of the same relay. Then the other side of the N.C. contact of the relay was wired to one leg of the N.O. contact of the push button. The other side of the N.O. contact of the push button stayed connected to the NEG lead on the coil. This completed the loop on the NEG side of the battery. The POS side of the battery was wired straight to the POS terminal of the coil. What happened is I got a hum from the relay and no spark what so ever.
I was thinking that if a V-8 car engine revs to 7000rpm that would be 933.3333 sparks per second. I would think that the relay would not chatter that fast but then again I think I am trying to use the relay for something it was never intended to do. Any ideas on how to achieve the multiple spark with common parts from an automotive parts store?
Darren
RE: Using 12VDC and a car coil to create an ignitor
TTFN
RE: Using 12VDC and a car coil to create an ignitor
darren
RE: Using 12VDC and a car coil to create an ignitor
http://www.cabelas.com/information/Gifts--Furnishings/Olympian-Continuous-Ignition-Multi-Spark-Ignitor.html
TTFN
RE: Using 12VDC and a car coil to create an ignitor
RE: Using 12VDC and a car coil to create an ignitor
Use the pushbutton to activate a normally open relay. The N.O. relay connects the output of the distributer to your sparking mechanism.
Is this correct?
RE: Using 12VDC and a car coil to create an ignitor
there is no distributor involved. that is what i am trying to eliminate. for simplicity sake this is a one cylinder engine that needs a continuous spark as long as the push button is pushed.
skills,
thank you. i will try this tomorrow.
darren
RE: Using 12VDC and a car coil to create an ignitor
RE: Using 12VDC and a car coil to create an ignitor
Re: "know that a dist and a DC motor will do the trick but it is not feasible in the field." There's no reason you couldn't stick the motor & distributer in a purged enclosure.
There's lots of igniters available for natural gas burners. Why are you trying to build one, especially if this really is an XP installation?
RE: Using 12VDC and a car coil to create an ignitor
The 555 idea is a good one. Lookup se555 data sheet for instruction on how to use one. It only takes a couple of caps and resistors to build the circuit. A se555 will handle up to 18 volts so a 12 battery will be fine. You'll have to add a output transistor circuit to get enough power though, try using a couple tip121 darlington transistor (high gain 4amps capable)mounted on an heat sink to get started. To keep the output transistor from being damaged during the off time add a rvs diode across the coil Band on the + side.
You may also get away with using a turn signal blinking device from a car to get an oscillator to drive the output transistors. Keep in mind that you'll need some extra current to make the blinker work as it takes current to heat the bi metalic strip inside the blinker device to oscillate.
-elf
RE: Using 12VDC and a car coil to create an ignitor
RE: Using 12VDC and a car coil to create an ignitor
peebee,
The motor and dist in the panel are out of the question. This is something that a company like Shell or PMEX would be looking to purchase. The Class I Div II rating is at these company's request so that is the rating I have to deliver.
brlewis,
These companies have specific ways they want the heater to be lite. This is usually with an ignitor rod and it is at the tip of the pilot assembly. This then lights the burner which can be anywhere from 150M Btu to 12MM Btu.
Again thanks for the ideas and I will let you know how it works out.
Darren
RE: Using 12VDC and a car coil to create an ignitor
This is how it works. When the switch is closed, the current flows through the contact point, to armature and the primary coil creating a closed circuit creating an electomagnet. The magnetized core then pulls the armature, thus breaking the circuit. When the armature returns and connect to the contact point, the circuit is closed again, the coil is magnetized, thus having a continuos on and off cycle. This creates a pulsating DC in the coil. The pulsating DC creates magnetic flux and transforms the battery voltage to a high secondary voltage depending on the ratio of the turns between the secondary and the primary. The higher the ratio, the greater the induced voltage in the secondary. However a capacitor is needed between the the contact point and the armature so as to prevent the contact point from damage or pitting due to induced current.
I just dont know if a 12 volt dc door bell placed in series with ignition coil and battery will work. If it works, this will serve as your on and off machine to create pulsating DC to the ignition coil.
RE: Using 12VDC and a car coil to create an ignitor
A solid state system would be preferable in a production environment, but getting reasonable transient protection on a 555/transistor solution requires allowing the input of the coil to swing about 300 volts in most cases.
Relays will arc a bit, but tolerate high voltage transients quite nicely in the short term.
If arcing is excessive, an ignition timing capacitor across either the coil or the points will reduce arcing, and are available at auto-parts places.
I'd like to watch a 12M Btu burner burn.
Sounds like thermal adrenaline.
RE: Using 12VDC and a car coil to create an ignitor
RE: Using 12VDC and a car coil to create an ignitor
The reason for reinventing the wheel is that my client requires a Chevette not a Corvette. I can build a Class I Div II ignition system for $200 whereas I can buy a system for $400 from a vender. I can build a Class I Div I igintion system (read NEMA 7 enclosure) for $800 or buy one for $1600+ from a vender. We are building 4 to 5 of these heaters a week so it adds up.
Darren
RE: Using 12VDC and a car coil to create an ignitor
RE: Using 12VDC and a car coil to create an ignitor
RE: Using 12VDC and a car coil to create an ignitor
Good Luck,
Engin
RE: Using 12VDC and a car coil to create an ignitor
good luck,
Doug
RE: Using 12VDC and a car coil to create an ignitor
THE BUZZER
12V+ to push button
other side push button to relay NC1
other side of relay NC1 to relay coil
other side of relay coil to 12V RTN
THE IGNITOR
12V+ to coil+
coil- to relay NO2
other side of NO2 to 12V RTN
KEY element!! Exactly as BrianR said you
MUST put a "coil condensor" (the standard coil
capacitor) that would normally be used on that
coil. With out the "condensor" you'll get diddly squat.
The condensor goes from NO2 to the other NO2 just like
the condensor across a distributors points.
This WILL light up your life!
Have fun.. Stand back.