HV school project

[Someone Electro]

20Khz is not all that high.Almost all transisors can switch good over 1Mhz(1000Khz)

The flyback circuit only reqires 1 or 2 power transistors.

The flyback cirucit cod porbobly also be made whith MOSFETs that produce less heat.

 

[Nigel Goodwin]

Daniels, in England older TV flyback transformers operated at a lower frequency.

Strange idea?.

UK 625 line TV's operate at 15,625Hz, HIGHER than the NTSC system used in North America.

If you're talking about the wrong obselete 405 system, that had a lower frequency - but it's so long ago I can't even remember what it was?, for that matter the long obselete French 819 system was higher.

Computer monitors operate at all sorts of different frequencies, you need to check the manual for a list of what they are.

Some modern sets, the so called '100Hz' models use double the line frequency, personally I've never seen the point behind it? - they simply show the same picture twice, to avoid 'flicker' - I can't see 'flicker' on a normal TV, and we don't get any complaints of it. What we do get is complaints about picture quality on 100Hz sets, they generally are a worse picture than 50Hz ones.

 

[audioguru]

Yeah, I saw those few scanning lines on the old UK 405 system and clearly heard its oscillator that drove me nuts. In fact when I was young nearly every TV's oscillator and "ultrasonic" alarms drove me nuts. I couldn't hear bats though.

I like the new progressive-scan like-doublers in new large screen TVs. The flicker of a single thin bright interlaced line on an ordinary set is intolerable. Over here the flicker is at 30Hz, in the UK it is at only 25Hz, isn't it? Many TVs "fuzz" their vertical amp so you can't see the individual lines and their flicker.
I modded my 1st colour TV (built in 1971, I still have it and it works fine) to have rock solid sync and its scanning lines don't budge on the screen. With other mods to its video amp it looks really clear. Decoding the old analog scrambling on it was fun and entertaining. :lol:

Now I have digital cable TV that I can't de-scramble. My cable co. called me the other day and said I have a problem with it. Oh yeah? No I didn't, when they called the week before to say the same thing I got a new digital box that worked fine. Its 160GB hard drive runs and records all the time! It's my own instant replay machine.
The technician arrived and measured a very low signal strength. He said he was ordered to give me a temp line strung up in the trees until they dig a trench for a new buried cable next spring. Because I could have keyed-in to watch a digital pay-per-view but the low signal from me messed the address to where they send the bill! :cry:

 

[danielsmusic]

what about the ignition coil from a car? (for the old distributor style ignitions). I saw this project in a magazine and thats what they used.

wow i never thought if that but it won't generate the type pf spark i want will it?

 

[danielsmusic]

i car in ignition coil has its own occilator in it as well

 

[audioguru]

i car in ignition coil has its own occilator in it as well

Nope. No oscillator. The engine rotates a cam for the points (they transfer the HV to each spark plug) and when the cam opens a switch that powers the primary of the ignition coil then the collapsing magnetic field generates a voltage that is stepped-up by the secondary. You need an oscillator to drive a power transistor to drive the primary.

 

[audioguru]

It will be the smallest Jacob's Ladder ever made. Its spark will stretch about 1cm, maybe 2cm if you're lucky.

 

[danielsmusic]

what about 2 of these coils connected together

 

[audioguru]

what about 2 of these coils connected together

You cannot connect two ignition coils together. The 2nd one will severely load down the 1st one. Besides, the coil is designed to produce about 20,000V output and a higher voltage would cause it to breakdown.

 

[danielsmusic]

20,000v would make a great jacobs ladder for my project it only needs to be an inch or 2 at the top

do you now how to work out what speed the 555 timer will need to occilate at for optimal prformence of the transformer.

 

[audioguru]

20,000v would make a great jacobs ladder for my project it only needs to be an inch or 2 at the top

Have you seen any project that uses a car's ignition coil in a Jacob's Ladder? One on the web uses a transformer from a big neon sign. The author says its 20,000V/50mA output is great, but another transformer with only 30mA is lousy. Calculate their enormous power and youll see why an ignition coil won't work very well.

do you now how to work out what speed the 555 timer will need to occilate at for optimal prformence of the transformer.

You do the calculation for a 6 cylindar, 4-stroke engine running at 3000 RPM.

 

[danielsmusic]

isn't there a formulae?

also i need help with the timer circuit, i have a led going through a 1k resistor to ground from output. and a 1k resistor going to the base of a npn transistor. the colector it at 9v and the emmiter goes to a bulb to ground. the led flashes but the bulb stays on, i found that if i take the bulb off while the led is on then put it back on when the led is off it will turn on at the same time as the led but stay on.

 

[audioguru]

Sure there is a formula for how many times there is a spark for a 6 cylinder 4-stroke engine. It is easy to figure out yourself.
Hint: In a 4-stroke engine, the crankshaft makes 2 revolutions for a cylinder to receive 1 spark.

If the LED flashes on and off but the light bulb at the transistor's emitter stays on, then you have the pins of the transistor connected wrong or the light bulb overloaded and destroyed the transistor.

What transistor?
What light bulb?
Sketch the transistor and how its pins are connected.

 

[danielsmusic]

formulea for working out how long it takes the magnetic field in a inductor or transformer in this case, to break down.

i don't know what transistor, 50v bulb but it works on a 6v battery barely

 

[audioguru]

You used a 50V bulb and tried to switch it with a little transistor?
May your transistor rest in peace. You overloaded the transistor with the bulb and now the transistor is melted inside and is shorted.

Next time you connect a load to a transistor you should calculate the load's current using Ohm's Law, to see if the transistor can drive it.

 

[danielsmusic]

the little transistor i had went into the base of a power transistor

 

[audioguru]

the little transistor i had went into the base of a power transistor

See, without your sketch of how it is wired and what parts you used, we are only guessing.

 

[pike]

How much voltage do you want, 1 auto-ignition coil is enough.
my spud gun has a 24kv output from a smallish 1.3amp/h 12vbattery. thats a gain of about 2000 times.
If you even succeeded in connecting 2 in series, you would obtain 48 million volts!! goodluck with that.

If you want some serious sparks, go with tesla coils.

 

[audioguru]

G'day Pike,
Please post your spud gun's schematic.
24kV jumps a gap of about 1cm, doesn't it?

 

[Nigel Goodwin]

G'day Pike,
Please post your spud gun's schematic.
24kV jumps a gap of about 1cm, doesn't it?

In dry air 10KV jumps 1cm, so 24KV would jump 2.4cm (or about an inch in 'real' measurements!).