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How I Made My Own Plasma Cutter From Junk

How to Build a Plasma Cutter

When I started assembling my cutter, I began with taking a good look at my parts list, later in this article. Once this was accomplished, I would study each the parts pictorial to get familiar with each part/component and they would be placed.

The next step was to study my schematic and create a layout diagram. My board layout diagram is the most valuable piece in the building, repairing, and modifying process of my cutter.

As I began mounting my parts, I organized my board into four sections. Those sections are Power Control, High Current DC, Low Voltage DC and High Voltage Arc Start.

Power Control
3KVA step down transformer and contactor. The transformer is mounted off board because it is big and heavy, as you can see in Section 13. The contactor became my first part on the board. I  wired it so when the head trigger is pressed, it turns the contactor on and allows my DC components to come on line. Then I began with my next system, High Current DC.

High Current DC
Bridge Rectifier
Large Capacitors
Reed Switch (which I used as a current sensor), what it does is allow the high voltage arc system to fire and as soon as high current starts to travel to the head and cutting starts it shuts down the high voltage arc system while cutting since it’s not needed at this point. If you lose your fire it restarts the arc and gets you going again automatically. My next system was placed on board.

Low Voltage DC
The low voltage DC components are mixed with power switch and 120 volt terminals.
Power Switch
120-volt terminal blocks
12 volt transformer
Low voltage bridge rectifier
Auto relays
Terminal strip, 4 position is all I needed but 5 position was what I had in my toy box.

High Voltage Arc Start
Microwave capacitor or run capacitor, a household dimmer switch rated for 15 amps. A Ford or Chevy ignition coil. I used the Chevy on this cutter. As you can see, I have terminals to all parts that get an external connection outside of their system so all I have to do is run a piece of wire in-between. When wiring all my components, I used my Chevy board layout diagram to run my wires.

I checked and rechecked all wires before mounting external parts. If you go to the final wiring section, you will also find pictures of my rigging of these parts. I could have done it many different ways, but this is what I chose at this time.

It took me about 3 hours of procrastination to finally assemble it all. You know how it is on a project, once you are ready with all your parts, your mind starts giving you a million ways of doing something. And, at last, you just pick a way and go with it.

Once I got it all together, I connected my air tank hose and put the pressure setting at 28 for a safe point to start. I fired it up and BAM – that baby didn’t need any more adjusting. It was cutting!
You can imagine all the relief and pride I felt when the Plasanator started kicking ass.

Yea, I said it Kicking Ass Baby. Oops Wife just told me I need to stop, hee hee and for all you creators – ah ah ah ahhhhhh.

I hope you enjoyed riding along with me in my journey.

Take care and be safe.  Remember, there are dangers in dealing with welding equipment.  If you make an attempt to build this Plasma Cutter you do so at your own risk.

The Plasmaman

Parts Pictorial

Parts to Build a Plasma Cutter
Fan is optional for cooling bridg rectifier on 240 volts. I only run 120 volts so didn’t use it.

Parts List

  • 3 metal or plastic switch boxes and covers for switches
  • 2 house switches
  • 1 dimmer switch 15-amp rating
  • 1 contactor 40/50 amp rating
  • 1 bridge rectifier, 700 volts 60 amps or higher (3 phase works great)
  • 2 electrolytic capacitors, at least 350 volts 2500 microfarads
  • 1 transformer 120 volts primary / 12 volt secondary rated at 2 amps
  • 1 low-voltage bridge rectifier, 50 volts 25 amp rating
  • 3 unversal auto 12 volt dc relays
  • 1 automotive ignition coil, Ford or Chevy
  • 1 microwave capacitor or any run capacitor, at least 120 volts 1 to 15 microfarads
  • 1 squeeze clamp like jumper cable end clamp for work clamp
  • 1 reed switch, 12 volt 1 amp rating, wrap 5 turns of 10 gauge strand around it and secure with tape or zip ties
  • 1 air valve, 120 volt
  • 1 air filter regulator (plumb to work on your set-up)
  • 1 plasma head with 2 pin leads rated 30 to 80 amps
  • 1 120 volt cooling fan like whats in a computer or microwave.  Does great for cooling a large rectifier (optional)
  • 1 5500 watt 220 volt water heater element. Use 2 in parallel for more amps or if you use 220 volt system
  • 1 step-up/step-down transformer, 240/120  3 kva for best protection
  • Miscellaneous Parts
  • wire ties
  • assorted terminal ends
  • assorted wire nuts
  • electrical tape
  • plumbing fittings for air regular set-up.  Your set up may be different than mine
  • about 10 feet of 16/14 gauge strand wire – 12 feet polyproelene tubing 1/4″ for tip wire cover
  • about 12 feet of 10 gauge strand wire
  • 1 large paper clip for tip wire connection to plasma head tip
  • 3/8 plastic tubing for head hose connection to isolate from electrode.

Chevy Coil Schematic

Chevy Coil Schematic
This cutter uses 13 amps to cut 1/4 inch steel. Uses isolation transformer for your safety. 20 amp line breaker required.

Chevy Board Layout

chevy board layout plasma cutter
This is the wire placement as I have it on the board. I have doubled up on some terminals, but you can have each individual terminal and then run jumpers.

Ford Coil Schematic

Ford Coil Schematic
This cutter uses 13 amps to cut 1/4 inch steel and uses isolation transformer for your safety. 20 amp line breaker required.

Ford Board Layout

Ford Board Layout
This is the wire placement as I have it on the board. I have doubled up on some terminals, but you can have each individual terminal and then run jumpers.


View of Board Mounted Components

View of Board Mounted Components for Home Built Plasma Cutter
Completed board parts minus air regulator. Air solenoid, water heater element and plasma head.

Power Control

Uses 3 kva step-down transformer, 120 volt primary and 240 volt secondary

3 kva step down transformer for plasma cutter
3 kva step-down transformer or step-up. Can be run 240 volts to 120 volts or 120 volts to 240 volts.

Transformer Connections to Board Terminals

Plasma Cutter Transformer Instructions
3 kva step-down transformer and main power switch connected to board terminals.

High-Current Section

Terminal Connections to Build a Plasma Cutter
120 volt leads to contactor terminal connections using 10 gauge strand wire.
Plasma Cutter Contactor Coil Connection
Contactor coil connection, jumpered to one side of contactor 120 volt connection.
Plasma Cutter Terminal Strip Connections
Terminal strip connections from contactor power leads.

Wiring for a Plasma Cutter

Wiring Schematic for a Home Built Plasma Cutter
High-current side wiring, contactor to bridge to caps to terminal blocks and feed back wire for voltage doubling. Notice capacitor positive/negative and bridge connections.
Reed Current Switch Plasma Cutter
Reed current sensor switch. 5 turns of 10 gauge wire then zip tie coils together and slide reed into middle.
instructions to build a plasma cutter
Reed switch wrapped 5 times with 10 gauge strand and connected to terminal blocks. Leads to terminal.

Low-Voltage Power Section

power switch for a plasma cutter
Power switch and 12 volt transformer leads to terminal connections.
Transformer for Plasma Cutter
12 volt transformer power connections to bridge rectifier and 120 volt terminal.

Relay Terminal Connections by Color

Terminal Connections Black Leads
Relays negative black lead connections.
Wire Connections
Relays white positive wire connections.
Relays n.o. yellow wire connections.
plasma relay connections
Relays n.c. red wire connections.


RElays blue wire, main contact connections. Only view blue wires from relay. All others for another step.


Ground Lead to Head Terminal

Ground Lead to Head Terminal
Ground Lead to Head Terminal. Can be in second or third position as arrows show.

Chevy Coil Stud Assembly

Chevy Coil Stud Assembly
Chevy coil stud mounting using zip ties, washers and nuts.


High-Voltage Arc Start System Connections


Plasma Cutter High-Voltage Arc Start System Connections
High Voltage arc start wiring for Chevy coil setup. Also shows relay and terminal strip setup
High Voltage Chevy Coil Wiring
High Voltage Chevy coil wire hook up. The white/black wire is your Head Tip wire.


120 Volt Power Lead to Relays for Air Solenoid & Arc Start

120 Volt Power Lead to Relays For Air Solenoid & Arc Start
120 volt leads to relays for air solenoid and high voltage arc start connection.
Air Solenoid Lead Connections
Air solenoid lead connections. I used lamp cord and divided at ends.
Air solenoid wire connections

Arc Tip Wire Assembly

Arc Tip Wire Assembly
Arc tip wire assembly. Solder, heat shrink tubing, paper clip and polyproplene tubing. Then just zip tie to head and hose.

Plasma Head Hose Assembly


Plasma Head Hose Assembly
Plasma head coupling assembly and tools. Electrode wire is in the hose and connected to coupling.
Plasma head coupling assembly and tools. Electrode wire in in hose connected to coupling.
Using flaring tool to flare copper tubing.

Final Wiring of External Mounted Parts, like the Head, Water Heater Element, Air Solenoid & Air Regulator & Work Clamp

Air Regulator for Plasma Cutter
Air regulator and solenoid with element rigging.
Plasma Cutter Rigging
Another picture of the rigging for the plasma cutter.
Final Plasma Cutter Wiring
100% done board. Notice how the high-voltage wire is raised to prevent arcing to the other wires.

Homemade Terminal

Homemade Terminal for Plasma Cutter

Author: Joe Eichholz

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