Please be advised that I offer this information for educational purposes only and will not be responsible for any use, misuse, accidents, mis-haps or other that may result from it. The adapter that is modified will lose any electrical approvals that are marked from the manufacturer. Obviously, the manufacturer cannot be responsible for the product after modification. When dealing with line power there is always a risk of electrocution. Please be very careful. This project requires some skills such as COMMON SENSE as well as basic soldering.
Electrolytic etching is a technique where electric current is used to remove metal from a substrate, in our case a steel knife. A Direct Current (DC) passes through a conductive solution which is called the electrolyte.
A very simple setup consisting of a battery, a couple of wires, a cotton ball and some salt water will remove metal from the knife wherever the current is allowed to flow.
Being that the battery is DC, this circuit will ETCH, but we can do better than this. If we have a little bit of Alternating Current (AC) available, we can also MARK or blacken the etch with carbon.
Before I get too far into the tutorial, I wanted to show you what Justin Boyd made with this style of etcher and a craft store stencil on a cleaver. Very cool!
Bill of Materials:
DC Adapter, 5 to 12 VDC, 1 Ampere or more.
Double pole double throw switch (Digi-Key)
6-32 X 1/2" machine screws.
6-32 nuts x 4
Small red ring lugs x 4
20 gauge wire. about 30cm (1 foot)
Piece of stainless steel for pad.
Some plastic or polycarbonate to hold the switch
Long flathead stainless steel machine screw
Nut to go on SS machine screw
Small block of wood
Rubber bands or cable ties
Soldering iron and small amount of solder
Drill & drill bits
Note: if this appears to be too complicated, try my simpler version here.
The main gear
The main component is the AC adapter. If you are like me, an old AC/DC adapter come from your junk bin of course!
This is the kind of adapter you want to use. Do not use the rectangular one's from modern computers as these are "switch mode power supplies" and will not have the AC available. We want the old kind that feels like it's got some weight to it. Try for at least 5 Volts DC and 1 Amp or more. My local 2nd hand store has these puppies for $2.
Below is a simple representation of how these old adapters work. They take the 120 Volts AC from your household receptacle and "transform" it to lower AC voltage. Then with diodes, the AC is rectified into DC and finally smoothed with a filtering capacitor.
The more you understand this circuit, the easier it will be to construct your etcher.
Let the fun begin! I opened this adapter up with a hacksaw. Carefully cutting around the seam. Do not go all the way through as you may cut some components. Rather, you want to get really close and then make the final cut with a utility knife.
This is what we are looking for. Here you can see the transformer and the circuit board.
Here I have identified the components as per the diagram.
This is a schematic of what we want to make. You see the same basic adapter with some additional items like a few wires, a switch, an alligator clip and a pad. What we really want to do here is bring out the AC along with the existing DC wires and connect the wires to a switch. The switch allows either AC (blue wires) or DC (red/black wires) to connect to the pad and clip.
Note: I use red to define the DC+ wire, but this may be black w/stripe as it's coming straight off the adapter.
First we are going to locate the output of the transformer and attached the blue wires like shown in the schematic. So where is the output of the transformer? Do you see the small copper wires coming out of the transformer going into the circuit board? Most of the time the wires themselves are holding the circuit board in place, but it's possible there may be some glue or tape around them.
Now I have located the output of the transformer, I get my wires cut and stripped and warm up the soldering iron.
These are the wires soldered on the pads where the transformer output connects. Be sure not to accidentally join another pad or leave a blob of solder somewhere it doesn't belong.
Here I have made a little room for the blue wires to come out. This will be right next to where the existing DC wires were coming out so watch the orientation of the cap.
The wires are out. A piece of tape will hold the cap on until we get the setup tested.
Wiring the Switch
The switch must be a Double Pole Double Throw type and will always have 6 pins. The part I had handy was a few bucks from Digi-Key, P/N EG2398-ND which is good for 5 Amperes and 120 Volts.
Attach the blue and black wires
Strip about 1/8 of an inch of insulation and press the wire into the hole. Apply heat from the soldering iron and then flow some solder into joint to make a good connection.
The blue wires are AC. The black and red wires are DC. Your wires may be also black and black with stripe. The solid black will normally be DC- and the black with stripe is normally DC +.
Connect a red and black wire to the two center terminals.
This means we are good to go. We can fix the switch to something that will hold it firmly.
Continued on Page II
(typical stencil artwork)