I have been searching high and low and cannot find anything - I have a small, high voltage curcuit board that will be housed in an earthed metal case (a DC trap for the incoming mains).
I have seen high voltage circuits where there is a thin sheet of stiff cardboard type material between the PCB and the enclosure - I am wondering if I should be using something like this too but don't know the correct name for it in order to be able to buy some. Or do I leave it out and in the unlikely event of any of the cables coming adrift from the PCB they simply short to earth via the metal enclosure and blow the main fuse?
I have seen high voltage circuits where there is a thin sheet of stiff cardboard type material between the PCB and the enclosure - I am wondering if I should be using something like this too but don't know the correct name for it in order to be able to buy some. Or do I leave it out and in the unlikely event of any of the cables coming adrift from the PCB they simply short to earth via the metal enclosure and blow the main fuse?
I think its a waxed type of card although I've never seen it listed as a spares or service item. There are diy alternatives and it might even be worth a look around a stationery department. I've used old Betamax cassette sleeves which are often thin plastic, old DVD RAM discs are often in flexible covers. Model shops maybe ?
The only name for that stuff that I have heard over the last 60 years is "fish paper". And google instantly finds it, here is an example:
560 - GC ELECTRONICS FIBROID FISH PAPER ELECTRICAL INSULATION | Newark element14
And unless your electrical code demands certain materials, there are other insulating materials, such as plastics. But as for wires coming loose, don't leave them unsupported. Even if the wire is only a couple inches, you can still bundle it with others and a tie wrap, or use a small cable clamp to the chassis wall. And instead of just soldering to the board, you can stake a solder terminal to the board, allowing you to wrap the wire end around it once before solder. There are a lot of ways to make something secure. Look under the hood of your car at how wires are handled.
560 - GC ELECTRONICS FIBROID FISH PAPER ELECTRICAL INSULATION | Newark element14
And unless your electrical code demands certain materials, there are other insulating materials, such as plastics. But as for wires coming loose, don't leave them unsupported. Even if the wire is only a couple inches, you can still bundle it with others and a tie wrap, or use a small cable clamp to the chassis wall. And instead of just soldering to the board, you can stake a solder terminal to the board, allowing you to wrap the wire end around it once before solder. There are a lot of ways to make something secure. Look under the hood of your car at how wires are handled.
I constantly get credit card offers that include a fake credit card in the envelope. Some are plasticized card stock, others are real plastic, but I save them and they are handy - if credit card sized - pieces of insulating material. Not the sort of thing I'd use commercially, but for my own stuff, I don't care if my insulator says Capital Improvements on it.
The proper name is "Presspahn" , not "cardboard" by any means.
Electrical Insulation, Thermal Insulation, Mica Insulation, Parts, Products, Materials - Presspahn Ltd
It's based on Kraft paper, that's why it's brown, but it's usually impregnated in phenolic rosin/wax/oil depending on application, to achieve very high electrical insulation.
Here's the lowest grade:
Presspahn Ltd - Products - Presspahn (Elephantide) - Grade K
Raw/untreated a 0.1mm sheet (printer paper thickness) breaks through with 1100 to 1500V ; when impregnated with 10kV
Of course it's often used way below that, both for safety and to cover lightning in the power lines and such.
The one you saw probably is 0.25mm or thicker, simply because it's very cheap anyway.
You can order it from transformer or motor rewinding supply shops , either in sheet form or in strips.
The other suggested insulating material is Mylar (Polyester film) sheets, again from the same sources but sometimes from Plastics dealing shops.
If you want just a small piece for an experiment, get a sheet of Laser Transparency film, which is also Mylar/Polyester.
Use a double or triple sheet, not strictly for electrical reasons (it's overkill) but just in case a sharp burr or edge *might* punch through.
In Electrical safety no caution is excessive.
as of:
No kidding.
Electrical Insulation, Thermal Insulation, Mica Insulation, Parts, Products, Materials - Presspahn Ltd
It's based on Kraft paper, that's why it's brown, but it's usually impregnated in phenolic rosin/wax/oil depending on application, to achieve very high electrical insulation.
Here's the lowest grade:
Presspahn Ltd - Products - Presspahn (Elephantide) - Grade K
Raw/untreated a 0.1mm sheet (printer paper thickness) breaks through with 1100 to 1500V ; when impregnated with 10kV
Of course it's often used way below that, both for safety and to cover lightning in the power lines and such.
The one you saw probably is 0.25mm or thicker, simply because it's very cheap anyway.
You can order it from transformer or motor rewinding supply shops , either in sheet form or in strips.
The other suggested insulating material is Mylar (Polyester film) sheets, again from the same sources but sometimes from Plastics dealing shops.
If you want just a small piece for an experiment, get a sheet of Laser Transparency film, which is also Mylar/Polyester.
Use a double or triple sheet, not strictly for electrical reasons (it's overkill) but just in case a sharp burr or edge *might* punch through.
In Electrical safety no caution is excessive.
as of:
it may land you in Jail
No kidding.
Thanks for all the replies (and the links)!
I googled for ages but obviously with the wrong search terms and got nowhere.
I basically have a small metal enclosure with a DC trap circuit inside and that is to be installed inside a power amplifier. If the caps blew I didn't want them spewing electrolyte all over the internals of the amplifier so I have put them in their own enclosure on a fibreglass board with tight point to point wiring underneath. Everything seems OK from a clearance point of view (i.e. live wires are at least 4mm away from the metal enclosure) but I just wanted something extra to insulate just to be sure.
Thanks again.
I googled for ages but obviously with the wrong search terms and got nowhere.
I basically have a small metal enclosure with a DC trap circuit inside and that is to be installed inside a power amplifier. If the caps blew I didn't want them spewing electrolyte all over the internals of the amplifier so I have put them in their own enclosure on a fibreglass board with tight point to point wiring underneath. Everything seems OK from a clearance point of view (i.e. live wires are at least 4mm away from the metal enclosure) but I just wanted something extra to insulate just to be sure.
Thanks again.
Just saw the thread and letting you know that a grill mat has a fibreglass mat as it's core with PTFE or Teflon coated or infused. If you go to this site you will see a variety of thicknesses; www.bbqezy.com or send an email and ask for an offcut if you don't need much. Cheers.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.