Author Topic: piezo ignition voltage?  (Read 7802 times)

0 Members and 1 Guest are viewing this topic.

Offline BANETopic starter

  • Supreme Robot
  • *****
  • Posts: 639
  • Helpful? 4
  • E=roboticsC^2
piezo ignition voltage?
« on: June 26, 2010, 08:01:35 AM »
So I'm trying to simulate the piezo electric ignition in a standard cheapo bar-b-que lighter.  First off i was wondering if anyone knew what about the voltage is in one?  I have a 12v 2800ma battery powering the robot so im thinking I would need a stepup transformer or capacitor array to the voltage to simulate the spark.  I tried hooking up my voltage meter but it only goes up to 600v and i know its probably in the kilovolts.  Any ideas?

thnx

update
http://rimstar.org/materials/piezo/ignitor1.htm


Offline BANETopic starter

  • Supreme Robot
  • *****
  • Posts: 639
  • Helpful? 4
  • E=roboticsC^2
Re: piezo ignition voltage?
« Reply #1 on: June 26, 2010, 08:07:40 AM »
just found this:
Piezo electric BBQ lighter High Voltage

it says aprox 15kv.  Now how to generate 15kv off a 12v for a split second?

Offline klims

  • Robot Overlord
  • ****
  • Posts: 188
  • Helpful? 2
Re: piezo ignition voltage?
« Reply #2 on: June 26, 2010, 10:22:17 AM »
Don't know about running off 12v, but the plasma cutters we have at work produce a spark using a tiny gizmo that produces very high voltages. If you think it might be useful I can probably grab a part number or something on Monday.
Otherwise I'm pretty sure back emf produce some pretty high voltage spikes. Don't know if it would be enough though

Offline Ro-Bot-X

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 1,431
  • Helpful? 25
  • Store: RoBotXDesigns.ca
Re: piezo ignition voltage?
« Reply #3 on: June 26, 2010, 10:31:07 AM »
Use an motorcycle ignition coil (and cap) with a spark plug. The ignition coil has 2 pads, one for ground, connect the capacitor ground there too, and the other for positive, connect the capacitor's other lead there. You connect the ground to the battery negative and use a high amperage switch (the car uses a platinum switch) connected in series with the battery positive and the coil positive pad. On the top of the coil use one of those thick wires to connect to the spark plug; the spark plug also needs a ground connection on the thread. You flip the switch ON, the capacitor will charge, wait a little and flip it OFF. The capacitor will discharge through the coil which will produce a high voltage that will discharge through the spark plug.
Check out the uBotino robot controller!

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: piezo ignition voltage?
« Reply #4 on: June 26, 2010, 09:46:01 PM »
Hi,

A trigger transformer from a strobe light or a camera flash (perhaps gut a cheap single use film camera) should do, but don't feed too much power, or it may break down.

Most important for a good flashover is a fast rise time, so the HT won't bleed off in corona discharge and sharp pointy electrodes so the electron concentration will be high.


Forgot to mention:
The reason the person in the linked web page doesn't see more than 240V (and up to 500V) is because his 'scope is not fast enough. A piezo pulse is very very steep (few ns range) and in the killer-volt range.
« Last Edit: June 26, 2010, 09:52:43 PM by Soeren »
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Conscripted

  • Robot Overlord
  • ****
  • Posts: 291
  • Helpful? 10
Re: piezo ignition voltage?
« Reply #5 on: June 28, 2010, 07:59:02 AM »
A trigger transformer from a strobe light or a camera flash (perhaps gut a cheap single use film camera) should do, but don't feed too much power, or it may break down.

I once got a few of these from wallgreens. I went to their photo department and asked for them. I then used the flash circuit in a simple coil gun.

Conscripted

Offline BANETopic starter

  • Supreme Robot
  • *****
  • Posts: 639
  • Helpful? 4
  • E=roboticsC^2
Re: piezo ignition voltage?
« Reply #6 on: June 29, 2010, 11:34:18 AM »
thanks guys for all the help,  so i've found the best, lightest, simplest way to generate 15kv for a split second is to......drum roll...use the piezo igniter that came with the torch.  I'll I've done was use a strong servo with a lever to press the trigger on the touch. lol      I'll post a pic of what i've got soon.  And it works great and is much lighter than a flyback transformer or ballast for a neon light sign. However, it does take about a second for the servo to press and hold, but i can live with that. 

Offline BANETopic starter

  • Supreme Robot
  • *****
  • Posts: 639
  • Helpful? 4
  • E=roboticsC^2
Re: piezo ignition voltage?
« Reply #7 on: June 29, 2010, 12:02:07 PM »
its basically a piece of folded/welded sheet metal with a servo bracket and fuel tank/piezo igniter.  It makes a perfect butane torch or a robot that want to take over the world lol

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: piezo ignition voltage?
« Reply #8 on: June 29, 2010, 04:23:18 PM »
Hi,

[...] it works great and is much lighter than a flyback transformer or ballast for a neon light sign. However, it does take about a second for the servo to press and hold, but i can live with that. 

A HT transformer from a single use film camera, a cap, a transistor or SCR and a few resistors would have been smaller and lighter than the servo and honestly... Using a servo is a bit too Rube Goldberg for my taste.

You may find this page on using a camera flash circuit usefull.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline BANETopic starter

  • Supreme Robot
  • *****
  • Posts: 639
  • Helpful? 4
  • E=roboticsC^2
Re: piezo ignition voltage?
« Reply #9 on: June 29, 2010, 07:42:28 PM »
thanks, thats actually something what i had in mind in the beginning.  However, the gap the spark needs to jump is close to 1/4" inside the ignition chamber.  Could the voltage generated by a camera flash be close to 15kv?  Now with that is just using that i all ready have; really i could use anything that makes a decent spark and make a smaller gap in the ignition chamber.  Another thing, how long does it take to charge the capacitor in the camera circuit?

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: piezo ignition voltage?
« Reply #10 on: June 29, 2010, 09:22:25 PM »
Hi,

However, the gap the spark needs to jump is close to 1/4" inside the ignition chamber.
Oh, I guess we're talking spudgun here?
If that's the case, here's a few car engine (CE) facts to compare with.
In a CE, the gas (gasoline+air mix) is compressed at the time of ignition, making it much harder to generate a spark and to ignite the gas - an ignition coil system that will make a spark of 10mm from a loose ignition wire to the motor block, may still be too weak to make a 0.8mm spark under the compression, in a spudgun it isn't compressed.
In a CE, the spark gap is usually between 0.5mm and 0.8mm, but still firing the gas correctly.
You'll need at least around 10kV to 12kV with a fast rise time for a 0.25" gap in a spudgun


Could the voltage generated by a camera flash be close to 15kv? 
It would probably take some redesign to make it powerfull enough, but it should be pretty high in voltage - it's the output from the trigger transformer for the flash tube that you use, not the voltage generated for the tube itself (which is just around 200V to 400V).

You could use a smaller gap and two sharp needles pointing towards each other will help the spark jumping.


Now with that is just using that i all ready have; really i could use anything that makes a decent spark and make a smaller gap in the ignition chamber. 
I'm not sure a piezo unit from a lighter will have much power spanning 1/4", but if you want to use it, you could remove the hammer and hit it with a small solenoid.


Another thing, how long does it take to charge the capacitor in the camera circuit?
That depends on how much current you supply.

The formula is: C = As/V
C = capacity in Farads
A = current in Ampere
V = voltage
s = time in seconds

This can be used to establish the capacity value of the cap as well, as usually, unmarked caps are used.
If possible, use a couple of caps, to keep the voltage high during sparks.

A xenon (flash) tube goes low impedance when triggered and unlike expensive flash units, disposables haven't got a turn off, so the tube drains the cap completely at each flash. When you just use it to make sparks from the HT transformer, you just use a small charge.

Instead of giving off a single spark, use an oscillator to generate a burst of say 10 to 30 pulses.
In a CE, you need around 1.0ms to 1.5ms of spark time for reliable ignition with an oldfashioned Kettering system, so if you generate a train of 10 kHz to 30kHz pulses, the gas will ignite if the mixture is good - no  more misfires.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


Get Your Ad Here