Reibot - Easy High Voltage - ReiBot

(hp://reipooom.les.wordpress.com/2011/05/schematichv2xed.jpg)

A quick view of driver circuit.

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The discoveries of an Electrical Engineer

Easy High Voltage

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Arcing slightly over 1.5 inches! Videos at the end.

Maybe you want to make a Jacobs ladder, or give your robot a amethrower. This is a simple guide on how to make high voltage from 12v capable ofarcing over an inch! Not only that, but my guide will also show how do this in a way which wont break down, and its completely solid state! Im notgoing to dive into frequency response or the concepts behind a yback and why it uses a ferrite core. There needs to be a high frequency (~20khz) squarewave signal controlling the driver, and Ill be using an Arduino. If you dont want to use an Arduino, then use a 555 timer or any other micro controller.

Note: if you already have a yback transformer removed and know how to be safe with high voltage, then skip to The Build Plan: This post is a tadlong =/

The project will be designed around a transformer. A high voltage transformer needs to be selected, but where to start? There are a few householdappliances which may be laying around the house that use a high voltage. Lets look at a few:

Selecting transformer:

Microwave Transformer:

Pros: High current, easy 60hz, designed for high voltage,2nd winding usually isolated

cons: Weighs A LOT!, its huge, and it only takes 120V toabout 2-6kV

Standard Transformer with high secondary to primary turn ratio:

Pros: Usually small, easy 60hz, easy to nd, cheap.

Cons: Its not designed for high voltage, expect rapid insulation deterioration.

CRT Television/computer monitor yback transformer:

Pros: Fairly small, light, designed for 15-50kV, easy to add a new primary, usually outputs DC!Cons: complicated pin out and overall hard to reverse engineer, High frequency 10+kHz.

Neon transformer/oil burner transformer:

Pros: fairly safe, designed for 15-50Kv, designed to run/last a long time, usually easy 60Hz.Cons: requires 120V, hard to modify (often inside a metal can), high current dangerous output.

Xray transformer/Pole Pig:

Pros: MONSTROUS (hp://www.youtube.com/watch?v=M8mjC_Inrj0)voltage/power, designed to run/last a long time, usually easy 60Hz.Cons: Unless youre a mad scientist, you probably dont have one lying around the house. Good luck nding one cheap, huge size/weight, and youllkill yourself.

Listed above are some of the options that immediately come to mind. Sometimes the transformers in a laptops back light is an option, but they dont tend

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where to cut the PCB with a pliers

to last long when operating in the 10+kV range. Looking at the pros and cons of various transformers, I decided to go along with a computer monitoryback transformer. I dont know the pinout and Im guessing the ybacks primaries are designed for higher voltages, not the 12V we want to use. Lets

add a new primary to simplify things.

Removing the yback:

If youre a reader who wants to actually do this on your own heres the rules for safety. If you dont want to read, heres a good video guide on howdischarge: hp://www.youtube.com/watch?v=bDAiLtTDuf4 (hp://www.youtube.com/watch?v=bDAiLtTDuf4)

Unplug the monitor and make sure it is not touching anything metal or conductive Glass face down.1.

Most importantly only use one hand, preferably your right, when touching ANYTHING! NEVER use both hands, so if you were to get shocked the

electricity wouldnt travel from one hand to the other. If electricity went from your right hand to your feet, your heart *should* not have too muchcurrent running through it.

2.

Stand on something plastic at least two inches thick and dont touch anything metal or conductive.3.

Common insulators will fail at these voltages. Treat all wiring as if there is no insulation on it.4.

Wear safety glasses, ear protection, and a thick long sleeve shirt. This is a large glass tube with a vacuum inside. If it popped there may be shrapnel.

The front is very thick and extremely safe, but the tube is not designed to be safe at the back end.

5.

Dont do this if youre using any sort of electronic life sustaining gear: pacemaker, insulin injector. Find someone else dumb enough to do it for you6.

Understand that youre doing this at your own risk, and I dont guarantee safety. I will not be liable for any computer/equipment damage or

injury/death. Ive been shocked by high voltage capacitors in the past and probably would not be here right now if I didnt follow the rules above. Do

not shock yourself even in nonlethal ways! you can still do nerve damage just shocking your hand!

7.

The CRT monitor has two main high voltage capacitors: the ybacks internal capacitor, and the glass tube itself acts like a capacitor. When you open themonitor there will be bare no insulation grounding wire running around the perimeter of the glass tube (near the screen viewing side), and theframe for the electronic boards should be metal too. Get some wires with alligator clamps at the ends and connect the tube frames bare ground wire and

the electronic boards frame. Now get a third alligator wire and clamp it to the grounded frame, and the other end to a at head screwdriver. Thisscrewdriver should have a thick plastic grip without any cracks! Hold the plastic screwdriver by the plastic end keep away from anything metal andwobble it under the suction cup electrode on the glass tube. You will eventually hit metal, if the monitor was recently on, possibly hear an electrical pop.Put down the screwdriver and pinch the back of the suction cup and pull it o. Remember to do this with a hand tied behind your back. Once its o,

touch the metal again with the screw driver and then connect the frame grounding alligator wire to the metal electrode. Now prod around the circuitboard with another wire connected to the frames ground to make sure nothing else is charged. After you feel as though youve poked the poormotherboard enough, congrats! its *hopefully* discharged! Now cut all the wires connecting the motherboard to the monitor, and I suggest you tie aframe ground to the pliers. Wriggle the motherboard out of the monitor and close up the monitor with just the glass tube inside and carry it to the trash.

(hp://reipooom.les.wordpress.com/2011/05/f1.png)So here we can see part of the motherboard for themonitor. The big black box front and center is the yback transformer, as you probably guessed.

I nd it easier to get some heavyduty pliers and cut around the

transformer. Once thetransformer is out on its ownlile PCB section, try to cutsections in between the pins. The

PCB will tend to crack, but wecan use this to our advantage.

Once there are lile PCB islands with only 1 or 2 transformer pins, de solder the sections.

The build plan:

Wire the new primary coil (hp://reipooom.les.wordpress.com/2011/05/f3.jpg)1.

design a circuit to drive our new primary coil2.

write the software for the micro controller managing everything3.

test it! (safely)4.

Wiring a new primary coil:

This is usually very easy and you can start o with some thin wire just to test the transformer and driving circuit. The ferrite core is often exposed quite abit and easy to wrap a new coil around. I wrapped a thin layer of masking tape, then a layer of electrical tape. I then used four layers of copper tapenormally used for stained glass, and I was sure to solder the ends together.

Why did I use copper tape? Mainly due to the skin eect. Electricity tends to prefer the surface of a conductor at higher frequencies. This is why a Teslacoil operating around 1Mhz will mainly burn and not electrocute. This is also why some high frequency lines are pipes lacking any sort of core!

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Image from Wikipedia

I looked over the equations and constants used and they agree with my physics book: Essential University Physics by Wolfson Volume 2. Its also wise tocheck an ensure that graphs match up with the equations when looking at questionable online sources, which in this case, the graph and equation did and

were from Wikipedia.


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Image from Wikipedia


even a quick wiring works, but gets hot!


older non rectied yback


That pin is a capacitor connected to the red high voltage output

What a nice primary! A lile hot glue to hold it in place.

(hp://reipooom.les.wordpress.com/2011/05/schematichv2xed.jpg)

driver schematic (click to enlarge)


minimum layout on breadboard. Large capacitor on 12v line

Designing the circuit:

There are many dierent

ways to build a ybackdriver. Mine uses a microcontroller, in this case anArduino, and a high

power N channelMOSFET. This makes thecircuit extremely simple tobuild and only has a few

components. Were goingto be running this circuit ataround 20kHz with a lot ofcurrent. To make things

simple Ill be using aMosfet Driver, and this will

allow usto easilyachieve12v

gate-source voltage dierential to minimize drain-source resistance, and the driver willquickly charge and discharge the gate-source capacitance, since its a high current halfbridge.

Mosfets Ive had great luck with:

IRFP260N (hp://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&productId=670101&catalogId=10001&freeText=IRFP260N&app.products.maxperpage=15&storeId=10001&search_type=jamecoall&ddkey=hp:StoreCatalogDrillDownView) N Mosfet,buy at jameco.com (//jameco.com) (best for this project)RFP30N06LE (hp://www.sparkfun.com/products/10213) N Mosfet, sparkfun.com Will function decently without a Mosfet driver

Mosfet Driver:

For a larger list, please visit my Guide to the MOSFET (hp://reibot.org/2011/09/06/a-beginners-guide-to-the-mosfet/)!(hp://reibot.org/2011/09/06/a-beginners-guide-to-the-mosfet/)

MIC4422 (hp://uk.farnell.com/micrel-semiconductor/mic4422yn/ic-driver-mosfet-9a-low-side/dp/1556746)-Driver, jameco.com (//jameco.com)

discontinued, type MOSFET driver into jamecos search. Farnell carries it!TC4420 (hp://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&productId=1291647&catalogId=10001&freeText=TC4420&app.products.maxperpage=15&storeId=10001&search_type=jamecoall&ddkey=hp:StoreCatalogDrillDownView) Has the same pinout as theMIC4422 and features great ESD protection. A direct replacement for the MIC4422.

Note: the ground of the Arduino and the driver circuit arealso connected.

Now for anyone experienced with Mosfets, youll see Imadding capacitors where they really shouldnt be located.

This will decrease performance ever so slightly, but from experience, willhelp protect the Mosfet and the driver. You may also want to wrap the

connected ground and signal coming from Arduino around a small choketoo.


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completed circuit board with a small heatsink


entire circuit

Test Code:

This will slowly increase frequency. Voltage may be measured by the arcing distance. Use an old computer for this or increase delay time in setup(); whichwill give you time to unplug your computer from the Arduino. If you need to see the frequency, use an LCD screen for the Arduino. I havent had issueswith this, but I wouldnt recommend using an expensive computer for this project! Notice how Im using a cheap netbook running from the baery.

Frequency sweep (pdf) (hp://reipooom.les.wordpress.com/2011/05/jacob_frequency.pdf)

Final Code:

Once youve found a good frequency, just use the tone generating function.

yback driver program (pdf) (hp://reipooom.les.wordpress.com/2011/05/jacob_ladder.pdf)

Remember that your yback transformer contains internal capacitors and needs to be discharged after use!

Word of Advice: Pulsing this circuit tends to have an EMP eect. If the Arduino crashes, its usually right when it was seing the registers/timers tooutput the signal. The computer on the Arduino will crash, but the registers may continue to output the signal which drives the yback. Be careful of this!

Components may over heat! The low voltage side may gain a net charge too which may shock you a bit when touching it. From experience this shock isusually mild, but you may want to earth ground everything if youre worried If the output voltage isnt very high, try reversing the polarity of theprimary coil since the transformer has an internal high voltage diode.

Want to measure the voltage? This is a tad bit dicult since the ybacks output is extremely noisy. I would suggest building a voltage divider

(hp://en.wikipedia.org/wiki/Voltage_divider) with 5 or so 10Mohm resistors in series and a 10k connected to ground. Have the voltage divider outputconnected to a capacitor. Run the yback and then when its o measure the voltage on the capacitor to calculate the yback voltage.

Some terribad quality videos!


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14 Responses to Easy High Voltage

Pingback: High Voltage: Controlling a yback transformer with an Arduino - Hack a Day

Pingback: High Voltage: Controlling a yback transformer with an Arduino

majdi says:

October 15, 2012 at 5:03 amHello, can this been modify for dc-cdi system?

ReplyMoser says:

October 24, 2012 at 11:41 pmyou could possibly replace a dc-cdi with a yback, but id be concerned about timing

ReplyKonstantin Izhykov says:

April 18, 2013 at 11:37 pmWell done! I really like the design and videos. Very good for experiments with high voltage.

ReplyMoser says:

April 18, 2013 at 11:47 pmBe super careful! That yback driver pulled 80 100 (when arcing) was at around 22khz when powered with an old xbox360 psu. Thats a TON ofpower for something like that. Thats death or severe burns if you make a mistake

Reply

Brandon says:June 23, 2013 at 6:11 pmVery well-wrien and easy to follow!

Is the high-voltage output from the yback transformer also at 22kHz?

(pardon my ignorance: a chemical engineering trying to understand how one might build a cold plasma driver @ ~20kHz, ~20kV)

ReplyMoser says:June 23, 2013 at 6:19 pm

will be DC unless youre using an extremely old yback. AC ybacks generally look like this

ReplyBrandon says:June 23, 2013 at 7:36 pm

From Wikipedia (hp://en.wikipedia.org/wiki/Flyback_transformer):

In older television designs, the transformer produced the required high voltage for the CRT accelerating voltage directly with the outputrectied by a simple rectier. In more modern designs, the rectier is replaced by a voltage multiplier. Color television sets also have to use aregulator to control the high voltage. The rectied voltage is then used to supply the nal anode of the cathode ray tube.

In modern displays, the LOPT, voltage multiplier and rectier are often integrated into a single package on the main circuit board.


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Whats coming out of the wire to the CRTs anode has most likely gone through a rectier AND a regulator. Shoot, I guess Ill have to lookelsewhere for a 20kV, 20kHz source!

Thanks for your help!

kd says:December 15, 2013 at 2:53 amHi Moser

Could you elaborate on the ways in which the extra caps and resistors protect the circuit?

Also is it necessary to have a MOSFET Driver?

RIght now I have an Arduino connected to the gate of a mosfet, The mosfet has its source drain powered by a 6V lead acid baery. Is there an extrafunctionality of the mosfet driver?

ReplyMoser says:December 15, 2013 at 6:59 amThe mosfet driver mainly improves switching eciency and in most cases improves Rds. Depending on your mosfet and current Vgs =5 is just ne.

Remember that the mosfet appears to be a capacitor. If that capacitance is large you can add a resistor to make it easier on the arduino. Youll needto look at atmega data sheet if itll be a long term installation or if failure is really bad.

For protection it all depends on what type of load. What are you driving and how much current?

Reply

kd says:December 18, 2013 at 9:42 pmThanks a bunch Moser!

Im looking to draw about 30W across an arc. Im curious what limits the current in these ybacks that I see arcing. Is there a resistor

somewhere in line with the primary coil? Because from intuition, my thoughts tell me that a yback that is shorted as in arcing, would simplydrive as much current through as is available from the primary circuit, and this current would proceed to likely blow the hair-thin secondarywires.

Moser says:

December 18, 2013 at 9:50 pmI never went into it that detailed. You should vary the duty cycle to limit power. Increasing the frequency should also limit current, but thetransformer will have sweet spots where it may draw a lot of power at certain high frequencies

Moser says:

December 18, 2013 at 9:50 pmI thought this was a dierent post. Yeah ainy will work just ne here. Use a mosfet driver to increase eciency

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