# Revisiting an arc lighter project

#### -live wire-

Joined Dec 22, 2017
956
I will go camping in a month or so and would like to have a working arc lighter by then. I also would like it to be DIY. I attempted this before but could not figure out what circuit to use. The goal is a powerful 30-40W arc with an absolute maximum current of 4 mA (mainly for safety reasons). That means probably 45-55 watts in.

I already have some small HV transformers, which I have modified to have less windings that can handle higher current (probably up to 10 amps, at least for a few seconds). I need to find out the approximate inductance and turn ratio.

For power I will probably get or make a 3s 18650 pack. While it may make it more expensive than commercial options, I could also use it for other projects.

My plan to figure out the inductance is to have an arduino drive a mosfet at 10s of kHz and 50% duty cycle. It will switch 10V or so and the primary and a 20 ohm resistor will be in series with it. I will measure the voltage across each of them and do calculations. I will then increase the frequency and drop the voltage to get .1-.2V (peak) across the primary. Then I'll measure the voltage across the secondary with my meter. It should give me the aproximate turn ratio with it being very lightly loaded. I will then modify it to have a turn ratio of about 1500.

So here is the main issue here. I want a fairly constant power of 30-40W a voltage range of 13-19kV. But P=V^2 / R. So with a constant impedance/resistance, the power is half as much at 9V than it is at 12.6V (the range of a 3s 18650 pack). 9^2 / 12.6^2 = .51! This is a graph of the current under a constant resistive load. This one is power, and this is current for constant power.

So I think I need to go with a circuit that combines a VCO and limits the input current by increasing the frequency when it gets too high. This prevents it from delivering dangerous amounts of current when a human is on the output. There would either be a center tap and two fets or a full H-bridge. The only issue is I do not really know how to go about designing such a circuit. I know you would need probably a shunt resistor and some comparators and passives, but do not know too much more. I could really use help making such a circuit. And do people think adding the current limiting feature is excessive, or that another circuit would be better here?

#### AlbertHall

Joined Jun 4, 2014
12,199

#### -live wire-

Joined Dec 22, 2017
956
The point is to do it DIY, not just to buy something! I want to design a circuit and have a good fundamental understanding of it. Also, what safety features does that one have? I do not want something that works but is unpredictable. And I want very powerful arcs. Can that easily ignite small pieces of wood?

#### -live wire-

Joined Dec 22, 2017
956
So... ideas for circuits?

#### oz93666

Joined Sep 7, 2010
739
I'm normally someone who laughs at death ...I ridicule those powerwall builders (18650s) who fuse every cell ....

But this idea has got me trembling ...and confused ???

You want to build a High voltage arclighter for starting campfires ??? perhaps in rainy conditions !!! Do you have a death wish???

What's wrong with matches ??? Or if you must do it electrically with a flash and a bang , whynot use low voltage supercapacitors in conjunction with 18650s?.

#### -live wire-

Joined Dec 22, 2017
956
Um... it will be current limited! Do you understand that power out < power in?!? It may be 15-20kV but it is limited to 10s of watts, meaning < 5mA. They sell arc lighters on amazon, etc. They will maybe give you a nasty shock and/or burns but nothing fatal. Do you really know what you are talking about?

#### -live wire-

Joined Dec 22, 2017
956
...

#### -live wire-

Joined Dec 22, 2017
956
Why is no one actually responding?

#### crutschow

Joined Mar 14, 2008
31,471
Here's an interesting do-it-yourself, simple carbon arc generator which should ignite just about anything.
Just don't look at the arc except with arc welder googles or you will get a nasty uv retina burn.
Even reflected light can be dangerous.

#### shortbus

Joined Sep 30, 2009
9,804
Why is no one actually responding?
Because it's not a practical project? You have a way to charge your arc starter but won't carry campers matches with you?

#### AlbertHall

Joined Jun 4, 2014
12,199
Albert I need to reach you
do you have an email?
or how i can ask you something in this site, maybe other way?
I dont want to interfer in this specif conversation.

regards

#### -live wire-

Joined Dec 22, 2017
956
I want to make one that uses HV arcs. It will expand my knowledge of circuitry and also it will NEVER run out. It is more practical than carrying 50 lighters around, @AlbertHall. And good idea @crutshow, except I want to avoid the danger of being blinded by it. So how do I make a VCO that also adjusts the frequency to limit the current?

#### ebeowulf17

Joined Aug 12, 2014
3,307
Why is no one actually responding?
Because you're asking very broad questions. If you'd designed most of your circuit and just needed help fixing some aspect of it, or overcoming one particular hurdle, you'd probably get help understanding that little tidbit, regardless of what project it was for.

But you have very little to show for your own efforts, and you're asking for a lot of design work on something that is potentially dangerous. If your project appealed to someone else on this site, they might put more of their time into the design work because it was interesting and satisfying to them... but since it doesn't seem like something that anyone else wants, no-one is likely to design the whole thing for you.

This project seems like it's too big of a leap for you to take all at once (no offence intended - it would be a daunting project for me too.) Why not try smaller projects you can safely experiment with while gaining experience? Work your way up, learning subsystems that would feed into this grand plan, until you have the experience and comfort level to come back with a more fully developed idea. Look for app notes from Analog Devices, Linear Tech, TI, etc. that give example circuits, with technical explanations, showing how to accomplish various design goals. Build and test sub circuits, getting help here along the way as needed.

As it is, you seem to be biting off more than you can chew, on a potentially dangerous project, that no one else particularly wants to sort out. I'm not saying you can't or shouldn't get help with it here, but you're going to have show a lot more work and background competency, with fewer blanks for others to fill in.

#### shortbus

Joined Sep 30, 2009
9,804
I'm not saying you can't or shouldn't get help with it here, but you're going to have show a lot more work and background competency, with fewer blanks for others to fill in.
No to mention putting limits on the projects outputs, that many of the off the shelf products don't have or use. This is one of those things that can't be done as cheaply or look as good as a store bought one.

#### -live wire-

Joined Dec 22, 2017
956
It's not just about price or looks, @shortbus.
Because you're asking very broad questions. If you'd designed most of your circuit and just needed help fixing some aspect of it, or overcoming one particular hurdle, you'd probably get help understanding that little tidbit, regardless of what project it was for.

But you have very little to show for your own efforts, and you're asking for a lot of design work on something that is potentially dangerous. If your project appealed to someone else on this site, they might put more of their time into the design work because it was interesting and satisfying to them... but since it doesn't seem like something that anyone else wants, no-one is likely to design the whole thing for you.

This project seems like it's too big of a leap for you to take all at once (no offence intended - it would be a daunting project for me too.) Why not try smaller projects you can safely experiment with while gaining experience? Work your way up, learning subsystems that would feed into this grand plan, until you have the experience and comfort level to come back with a more fully developed idea. Look for app notes from Analog Devices, Linear Tech, TI, etc. that give example circuits, with technical explanations, showing how to accomplish various design goals. Build and test sub circuits, getting help here along the way as needed.

As it is, you seem to be biting off more than you can chew, on a potentially dangerous project, that no one else particularly wants to sort out. I'm not saying you can't or shouldn't get help with it here, but you're going to have show a lot more work and background competency, with fewer blanks for others to fill in.
I know HV inherently has certain dangers, regardless of the current (UV light, possible nerve damage, and others). But regarding the risk of sever electrocution, if the output was limited to 2 or 3 milliamps, wouldn't the risk be minimal? And 2-3mA at 15-20kV is certainly enough power to ignite something.

So I actually CC seems simpler than CP, and more practical. I should have thought of it sooner.

So I will try and generate a schematic for this once I figure out all of the components required. I may have to draw it by hand. So there would be a shunt and op-amp that monitors the current. There is also a comparator, with a potentiometer for tuning. If it is less than the target, it is low, and somehow decreases the frequency. If it is greater than, it is high, and then tells it to increase the frequency. I could maybe have this charge a capacitor which automatically discharges when not being charged. This could control a VCO that drives the mosfets controlling the transformer. I could use a schematic for a VCO. Also, it would have to draw very little current from the control voltage (to not discharge it too fast).

This is just one idea. And I could also probably just do it with an ATtiny or ATmega328p microcontroller. That may be better since it would require a lot less hardware. The issue is, it still might require additional circuitry, due to the limitations of such a microcontroller.

#### shortbus

Joined Sep 30, 2009
9,804
I know HV inherently has certain dangers, regardless of the current (UV light, possible nerve damage, and others). But regarding the risk of sever electrocution, if the output was limited to 2 or 3 milliamps, wouldn't the risk be minimal? And 2-3mA at 15-20kV is certainly enough power to ignite something.
Just my own thoughts on this, and nothing malicious meant.

You seem to have a very different out look on electricity/electronics than me. All of your warnings on "arc flash" and similar things in other threads, leads me to believe this way. Like some one who reads things online and tries to apply that to every thing they respond to. Worrying about the number of milliamps going through the body also seems like this. How exactly will the amps go through the body in this project? How do both side of the circuit get connected to the body when this "lighter" is in use? Will a single side give a shock, probably, but is it going to be "lethal"? Very doubtful.

Getting shocked when working on a car engine from the ignition system happens. And to my knowledge no one has died from that. And that ignition system has way more voltage and amps that what your talking about. And it, the ignition system, even with much more power and voltage would be hard pressed to start a stick on fire like you seem to think your "lighter" will.

Do these off the shelf lighter light a cigarette, yes, would they light a stick on fire, doubtful. Do you even own one of the off the shelf lighters? If not, how do you know they will do what you think they will?