New Electro-Etcher design

[Atlas Knife Company]

Here are the plans for my latest etcher design. It is a bit closer to Chris Crawford's design than my previous design. The reason for the change is the lack of availability of 12VAC transformers. I've also changed to a rectifier instead of the DC transformer. It's the same amount of soldering, just smaller and cheaper. I've added a lighted arcade button to the plans, making it much easier to pulse etch the DC. The arcade button is designed to handle quick, repetitive pushing unlike other buttons. I've also added a small capacitor to the DC circuit to smooth the signal and increase the power output. Cost of this etcher is still under $25, excluding the computer power supply and cord.

Parts list:
Project box $5 at Radio Shack #270-1803
Power jack and cord from dead computer power supply - free, ask for a dead one at local computer shop
6" 8 conductor CAT-5 cable $.40 at local hardware store
6v/12v AC stepdown transformer $8 on eBay

DPDT switch $1 on eBay

Lighted arcade button $2.29 on eBay

16v 2200uF capacitor $.99 on eBay

2 position pushbutton speaker terminal $2.50 on eBay

2 amp Bridge diode rectifier $1 on eBay

Alligator clip leads $2 on eBay

The project box will be a headache. Not because they are hard to find, but because there are so many. I found a couple that were a bit more expensive, but just the right size that I wanted. This box is 5" x 2.5" x 2". Everything is a nice, snug fit. The arcade button is the limiting factor in this build, as it has only about 1/8" clearance in the case at 2.5" deep. Drill a 1" hole in the middle of the project box top. Drill a 1/4" hole for the DPDT switch and 4 holes to mount the push button terminal. Cut out a square on one end of the project box to mount the 110VAC receptacle.

The brief rundown of how to wire it. Electricity in from the power jack to the transformer. Transformer out to the switch AND rectifier. Rectifier out to the lights on the arcade button AND the switch. One wire out from the switch to the terminal, the other to the arcade button then to the switch. The circuit is only complete when the arcade button is pushed.

It's easiest to solder the rectifier first. Cut the blue/blue & white and green/green & white into 3" pieces. I used green and green & white for the AC, blue for DC+ and blue & white for DC-. Solder both 3" pieces of each color to the rectifier. Green and green & white to the middle pins of the rectifier. These are AC and are not polarized so it doesn't matter which one goes to which. Connect the blue to the +(positive) on the rectifier and the blue & white to the -(negative).

Solder one of the green and green & white wires to the end pins of the 4-pin side of the transformer. Solder the other green and green & white to one side of the DPDT switch. Connect the 2 middle pins of the 4-pin side together. Bend them and solder them together is the easiest way.

Solder one of the blue and blue & white to the other side of the DPDT switch. Solder the other blue and blue & white to the side tabs of the lighted arcade button. Solder the negative side of the capacitor to the blue & white wire on the arcade button and the positive side of the capacitor to the blue wire on the button.

Separate the orange and orange & white wires and attach them to the center pins of the DPDT switch. Keep the orange on the same side of the switch as the blue and green. This helps keep the polarity straight. Attach the other end of the orange & white to the black push button terminal. Cut the orange wire in half. Attach the orange wire to one tab on the arcade button. Attach the other orange to the other tab and connect it to the red push button terminal.

Lastly, attach the two 110VAC from the receptable to the 2 pin side of the transformer. Everything should now be connected.


Here it is, fully assembled

Here's everything needed to etch. The etcher, some salt, medicine cups, and q-tips.

Any questions, feel free to ask.

 

[Wloch248]

Wow, just wow. Very nice job. I know what my next project will be.

 

[Atlas Knife Company]

Bump for Philip and others.
This is the latest version that is available at a few retailers.

 

[phillip_o_w]

Thank you! I will have to TRY to build one of these!

 

[usmchawk]

I just finished building one and it works great. I will admit soldering those wires to the rectifier was a pain, but I finally got it done. The only thing I notice is that the capacitor is still holding a charge after the power is disconnected. I found this out when I put a small screwdriver on the pin attached to the arcade switch to move it over just a bit and it sparked. So I put my multimeter on it and sure enough. I don't think this is a big deal as it is closed up now and the charge will either trickle out or it will be spent during the etching.

Thanks for the great plans!

 

[Stacy E. Apelt - Bladesmith]

That is the norm with capacitors. In designing electronic circuits, there is often a bleed-down resister in parallel with the capacitor. On a low voltage circuit like this, it doesn't really matter. On some of the HV things I used to work on it could fry you.

 

[Atlas Knife Company]

Actually, in the design shown, the lighted arcade button should stay lit for several seconds after the power is unplugged depending on the size of capacitor you used. The LED acts as a draw-down and empties the capacitor entirely in about 30 seconds. I just finished building a batch of these for USA Knife Maker Supply, the should be on their website next week. The toughest part, as you mentioned, is soldering to the rectifier. I wrap everything together, apply flux liberally, and drop a glob of molten solder from a 250w gun on it. I found that I could destroy a rectifier of this size by using a smaller iron for a longer time to melt the solder. I know they say to heat the wire until the solder is melted by the wire instead of the iron directly, but the heat is transfered much better by molten solder than it is by hard metal. You go through tips much faster, but I can get the job done in a fraction of the time and tips are easy to make.

 

[rogerxd45]

please forgive my ignorince but what is this for? and please dont just say etching.

 

[Atlas Knife Company]

This is a device used to create 12vdc and 12vac at the flip of a switch and push of a button. DC current removes metal, AC current oxidizes the metal, turning it black.

 

[Stacy E. Apelt - Bladesmith]

It is used to etch your maker's mark on knife blades. You use a stencil and the etcher with an electrolyte.

 

[gotye]

So if I were to just put alligator clips on my 12VDC 200mA and plug it directly into the wall, would it short anything out? (first post, sorry for the amateurishness)

 

[tattooedfreak]

No because it already contains a stepdown, however you won't be able to switch AC/DC control.

 

[gotye]

I made a crude system using two old power chargers 1. 12VDC 200mA and 2. 16VAC 250mA, and I understand DC does a better job at etching, AC at oxidizing/darkening, though I could only get them to darken not etch. Do I need more power going to my device to actually etch?

 

[Atlas Knife Company]

That should work fine, although 12vdc 200ma is a bit on the weak side. It will just take a bit longer than a 1000ma supply. Here's a link to an etcher like the one you built, albeit probably a bit more fancy. It's the etcher that I first built and still use today even after building a couple dozen of the etcher from this thread.
http://www.bladeforums.com/forums/s...-Electro-etcher-under-20?highlight=diy+etcher

 

[AVigil]

I bought one of Zaphs Etchers. I bought a stencil from Ernie and some etchent from TruGrit and these are examples of my first attempt at a makers mark

I think it is a good combination.

 

[tattooedfreak]

Maybe Im just thick but I cant figure out your wiring. How many of each wire do you have and where are they going? I thought I could see it but mine doesnt seem to work.

 

[Atlas Knife Company]

The brief rundown of how to wire it. Electricity in from the power jack to the transformer. Transformer out to the switch AND rectifier. Rectifier out to the lights on the arcade button AND the switch. One wire out from the switch to the terminal, the other to the arcade button then to the switch. The circuit is only complete when the arcade button is pushed

Can you tell us how you have it wired?

 

[tattooedfreak]

Well, I tried to follow what was written but I had no idea how many wires I needed, so when I looked at the picture it didnt seem to match the instructions. It looks like you have multiple wires coming off the rectifier and I'm not really sure which wires are where on the dpdt (except for the orange). Oh and just to confuse the situation, I have an inline transformer so I only have the two power lines, no transformer.

 

[hickman1]

follow up question. Can a computer power supply be used for etching and darkening as well?

 

[Atlas Knife Company]

The rectifier gives off the the DC current, so it should have wires coming out to the lights on the arcade button and to the switch. Depending on your layout, you can attach the capacitor to the rectifier directly, or to the arcade button. In my current builds, I run two wires off of +/- on the rectifier and attach the capacitor directly. One wire to the lights, one to the DPDT. I attach a wire and transformer output to each ~ leg of the rectifier, that wire goes to the DPDT.

Well, I tried to follow what was written but I had no idea how many wires I needed, so when I looked at the picture it didnt seem to match the instructions. It looks like you have multiple wires coming off the rectifier and I'm not really sure which wires are where on the dpdt (except for the orange). Oh and just to confuse the situation, I have an inline transformer so I only have the two power lines, no transformer.

No, the computer power supply isn't a good choice. It will work, but not the best, cheapest choice. Follow the link from post #14 for a thread on using wall transformers.