Author Options:

Foam Cutter transformer...overkill? Answered

I have a Pyramid ps9kx desk top power supply for running 12v stuff...can I use this directly as a foam cutter or is this more of a breaker throwing foam melter?
Specs from Amazon;

5 Amp Hobbyist Bench Power Supply
Bench Power Supply, AC-to-DC Power Converter with Car/Vehicle Power Outlet (5 Amp) Features:Linear / Regulated Power Supply DesignAC-to-DC Power Conversion (12V DC)Provides Constant Source of DC VoltageSimple Electronic Plug-in OperationHassle-Free Screw Terminal ConnectorsEliminates the Need of Battery or External Power Source12V Car / Vehicle Cigarette Lighter Power Accessory Outlet ConnectorFuse Protected with Auto-ResetElectronic Overload, Short Circuit & Overload ProtectionUsed for Component & Device Equipment Testing, Operation & PerformanceRugged & Durable Housing Construction, Cabinet HeatsinkBuilt-in Cooling FanPower ON / OFF SwitchPyramid Compact Hobby Power Supplies Safe for Tabletop PlacementTechnical Specs:Amperage: 5.0 AMP (Constant), 7.0 AMP (Surge)Connectors / Hardwire Terminals: Red Positive (+), Black Negative (-)Power Output: 13.8V DCPower Input: 115V AC, 60Hz (70 Watt)Dimensions (L x W x H): 7.5'' x 4.9'' x 3.0'' -inches




1 year ago

Here is your help :-)


Answer 1 year ago

Whereas that looks fantastic, I had to google all those things ...and that doesn't really answer my question. I would like to use what I have not build something I have no idea about...especially if just the stancor p-6379 transformer costs 90 bucks, whereas the Pyramid runs $30... So, I still need to If I hook up a positive lead from the Pyramid ps9kx desk top power supply to one end of a steel wire, and the negative to the other end will it work to cut foam...that is the question.


Answer 1 year ago

A great deal depends on the steel wire resistance and length..

Some pictures of how I handled the wire extending when hot..

**** Click the pictures to see the whole image ****

I used a split bolt to attach copper flexible wires to the steel hot wire.

The chances that you will find the correct resistance on your first try are very small,

It (Resistance) can go two ways;

A) Too High (which is preferred) and then shorten the length..

B) too low and the wire can melt the wire or pop your PS fuse..

I used AC and adjusted with a variable transformer, you could use a power resistor in series or try different Gauge steel wires to match your power supply..

Yes you can do it but with a peak of 7A it will cut slower when you find the correct balance.

You may have noticed I avoided math because as the wire / rod heats up the resistance changes rather drastically and changes the current :-/

C-Tool2b.JPGC-Tool3.JPGConnection.JPGAdj StyroCkt.jpg25W-50-OhmWirewound.jpg

Answer 1 year ago

Added picture info about cutting styrofoam.. Yes, I simply use a wood dowel to hold a shaped hot wire (welding rod) to cut foam using gloves to avoid burning my hand.

The transformer isolates you from AC line and may run 7 volts at 23 amperes on the secondary and never gets more then warm.. The variac supplies 70 VAC AT 2.3 Amps AC.