MOSFETs to switch/cut-off 10000V

Hello from Spain,
I am an arduino newbie and this is one of my first proyects. I need a way to make a switch which can cut down a high-voltage line which is connected to one of the arduino pins, the line is usually off but it can go on at some times and I want to protect the arduino from this high voltage. The voltage I want to switch (i.e protect the arduino from spikes that would occassionally go into one of the digital pins) is a pulsed one with this maximum characteristics:
max voltage= 10000v
duration of each spike= 0.05 secs
Maximum charge per pulse= 2.5 mili coulombs
maximum energy per pulse = 5 joules
maximum current peak= 10amps

I've heard that you can use several MOSFETS in conjuction to be able to switch these high voltages but no further information or circuit drawings on how to set it up. Maybe mechanical relay would be another solution but I like the MOSFETs because the power consumption would be lower and that is an issue in my project.
Thanks in advance
Angel

Will the Arduino be connected to a computer?

no, it will be powered by a battery

You'll be hard pressed to find anything solid state to handle that kind of voltage commercially at a reasonable price.

A research company has recently developed a 12kV IGBT, but I dread to think what the cost would be to try and get hold of one.

Most commercially available devices top out at just over a kilovolt.

And no, you can't use multiple MOSFETs together to magically make them higher voltage. You can parallel them up to increase the current handling capacity, but not the voltage, and you can use lower voltage MOSFETs (or BJTs) to drive higher voltage MOSFETs, but the "end" MOSFET still has to be able to individually cope with the voltage across it.

What exactly is the project, and what are you attempting to do that requires such high voltages? Maybe there's a better way of doing what you want.

maybe make a BIG mechanical switch with a servo?

I am an arduino newbie and this is one of my first proyects.

Then forget it.
This project is way outside your skill set, and mine too. You will kill yourself if to try to do this.
There is just so much you do not know. Dealing with 10,000 Volts is not something you play with on your kitchen table.

Grumpy_Mike:

I am an arduino newbie and this is one of my first proyects.

Then forget it.
This project is way outside your skill set, and mine too. You will kill yourself if to try to do this.
There is just so much you do not know. Dealing with 10,000 Volts is not something you play with on your kitchen table.

I wouldn't know where to start, I'm sure "several MOSFETS" won't work though.

Why is a 10,000V line connected to an Arduino pin? What normally goes through it? The best way to protect the Arduino is to disconnect the wire and do it a different way.

Grumpy_Mike:

I am an arduino newbie and this is one of my first proyects.

Then forget it.
This project is way outside your skill set, and mine too. You will kill yourself if to try to do this.
There is just so much you do not know. Dealing with 10,000 Volts is not something you play with on your kitchen table.

Dare I say... Natural Selection...? ]:smiley:

This is an interesting read about high voltage thyristors which can switch 10Kv at up to 5000 A.
Devices like this are used in HVDC converter power stations where the HVDC can be as high as 800 KV.
People who work in this industry I really have high regard for.
Getting it wrong yields some horrible outcomes.
http://www05.abb.com/global/scot/scot221.nsf/veritydisplay/1402c60973f47e72c1256fda004aead8/$File/thyrvalv.pdf

Moderator edit: link corrected

Typically, you would use a transformer with a secondary winding ratio to generate 10kV from a much more sane primary winding voltage, which can then be switched via a common MOSFET.

That said, not to rain on your parade, but I agree with the voices of reason here. No way no how I would attempt this project myself. Nuh uh. 10kV is high enough to start overcoming insulating properties you take for granted.

nano coulombs at high voltages hurt, milli coulombs will be lethal. This is a task for
a vacuum tube device or spark-gap of some sort, or a VDR, followed by more
protection circuitry to reduce 100's of volts down to 5V... Basically a lightning arrester?

Protection circuitry is often passive since the intent is to absorb energy, not control it.

SirNickity:
10kV is high enough to start overcoming insulating properties you take for granted.

You're off by an order of magnitude. An appliance company I work with performs Hipot tests at 1KV (220V appliances). At that voltage the insulation starts breaking down. With enough elapsed seconds or a few dozen exposures... well... you know the rest.

4500V available - but as said above, have to worry about voltage arcing across wires & thru insulation.
That's way higher than guitar tube amps even, and those parts are pricey too.

http://www.mouser.com/Semiconductors/Discrete-Semiconductors/Transistors/MOSFET/_/N-ax1sf?P=1yy3xzs&Keyword=n-channel+mosfet&FS=True

Where is the 10k volts coming from? Is it coming in from power lines or are you talking about electric fences or protecting against static electricity (i.e. what is the dgree of danger)?

I've heard of metal oxide varistors (MOVS) being used to clamp high voltages going into electronics. Maybe someone else can expand upon this. I'm not sure whether these are the capsules used in WiFi antenna lightning arrestors (although these are usually sacrificial).

I Think somewhere the real point was lost or missed…

The voltage I want to switch (i.e protect the arduino from spikes that would occasionally go into one of the digital pins) is a pulsed one with this maximum characteristics:
max voltage= 10000v
duration of each spike= 0.05 secs
Maximum charge per pulse= 2.5 mili coulombs
maximum energy per pulse = 5 joules
maximum current peak= 10amps

This looks like a job for a Mov to me… a 1.5KE12 Varistor would do the job easily… Perhaps a little overkill…

Doc

1_5KE12.pdf (252 KB)

You're not wrong. It's the bit about wanting to switch it that threw us all - we all immediately fixated on that bit and started discussing methods of switching that kind of voltage.

But yes, a MOV (Metal Oxide Varistor) is the normal method for protecting fragile microcontroller inputs from high spike voltages. Also used on power inputs for line spike suppression.

Typically they look like blue ceramic capacitors, but they work kind of like an extreme zenner diode. At low voltages they are open circuit, but when you reach their avalanch voltage (in either + or - polarity) they become an almost direct short circuit. They protect agains spikes and HV transients, but aren't usually any good against lightning strikes - in a strike they are usually the device that has most obviously lost all its Magic Smoke™ and turned all Black-n-Crispy™.

If you take a look at, for example, an old Amiga 500 motherboard you can see that along the back edge of it there is a huge long row of MOVs - every single IO pin is protected against spikes, typically caused by static electricity from the user plugging things in.

Docedison:
I Think somewhere the real point was lost or missed...

The voltage I want to switch (i.e protect the arduino from spikes that would occasionally go into one of the digital pins) is a pulsed one with this maximum characteristics:
max voltage= 10000v
duration of each spike= 0.05 secs
Maximum charge per pulse= 2.5 mili coulombs
maximum energy per pulse = 5 joules
maximum current peak= 10amps

This looks like a job for a Mov to me... a 1.5KE12 Varistor would do the job easily... Perhaps a little overkill...

Doc

Thanks for all the replies!! It is true majenko I should have been clearer.

As MarkT, lemming and Docedison said there is no danger in these electric shocks, they are the maximum allowed specifications for the electric fences that are used to contain animals, I have received several times a “spike” accidentally while checking them or trying to jump over them and they are have strict regulations in the design as not to kill anyone, although they hurt, and make you wish not to touch it again… 10000v is the allowed maximum, the normal spikes are around 5000v depending on the electrifier. It is like receiving an electrostatic shock when you touch another person or a cars door that is “charged”.
So there is no danger for a human in receiving that shock. The project is to use the same line in the electric fence to sense at the other end of the fence connecting it to a digital pin in the arduino, when sense is received the arduino will connect the electrifier (I have already done that part of the project ), what I need know is a way to protect the arduino when the electric charger starts to work.
Seems that a varistor might do the job, I will give it a try, thanks !!
As CrossRoads said arcing across wires and thru insulation might be another problem, I’ve seen that happen in the fences when the cable gets very close to a metal post even it is not touching it.
Many thanks to all again for your replies, any other suggestions are welcomed.

So let me get this straight… What you are trying to achieve is:

  1. Someone / something touches the fence.
  2. The Arduino detects that touch
  3. The Arduino activates the electrification circuit
  4. The person gets a shock.

Seems a reasonable project, and one that could prolong the life of the battery somewhat I guess, and give more instant results as there’s no real time delay.

Personally I’d prefer to completely isolate the Arduino from the fence in that scenario. I’d probably look at a suitable relay that could switch the fence’s connection between the Arduino and the energising circuit. In its idle “NC” state it connects the fence to the Arduino for sensing. Then the Arduino activates it and it connects the fence to the energiser instead.

Of course, finding a relay that can cope with that kind of voltage / current could be tricky, and driving it may be just as problematic as the coil would probably be rather meaty.

One example that would fit the bill: http://www.te.com/catalog/pn/en/5-1618276-5?RQPN=K64C841 though they are out of stock with Farnell, and cost £4.5K!!!

I’m sure there are others if you look around.

mmm, that is a little bit over my budget...

found this one cheaper:
http://es.farnell.com/cynergy3/dat70515f/relay-15kv-5v-coil/dp/1877557
would it do the job?

what is wrong with the use of a varistor? it seems like a simpler solution

thanks again

That one would cope with a 5th of your peak current...

And I am paranoid. I like "belt and braces" approaches when working with high voltages :wink: