New Electro Etcher design

Atlas Knife Company

Atlas Knife Company

Joined
Feb 16, 2010
Messages
3,668
Well, years ago I made electro-etchers based on Chris Crawford's update to Bob Warner's design. It worked, but was cumbersome to build. Still, I always thought that while the design was solid, it could be better. It needed to be portable, and it needed to be just a few volts higher than a standard 12v transformer provided. I also wanted to build one that didn't rely on the ancient transformer technology that was the basis for the Warner/Crawford design.

So, I started from scratch with these requirements in mind:
  1. 15VDC etching ability (operating at 50hz pulse)
  2. 30VAC marking ability (get that sucker DARK)
  3. Battery operated
  4. Overall better performance than previous designs, while being smaller and lighter

I built a circuit based off a common 555 timer and an H-bridge to create a 30v square wave from a 20v DC input. In this case, that's a Ryobi 20v battery, but I plan to make other battery platforms available. This makes it a compact unit that is very quick to setup and takes up very little room in storage.

OK, I know what the experts are thinking: How do you have 50hz DC current? You understand that DC doesn't operate like that, right? Well, true, but I have it designed so that it does turn on and off 50 times per second via an IRF540, giving a 50hz pulsed operation. I've always found pulsing it on/off gave a better etch than always on.

Still early in the development, need to optimize the PCB a bit, and tweak the case design some more, maybe add an activation light, but I'm happy with it so far.


PCB_inside_v1.jpg
PCB_external_v1.jpg
 
That is really cool. The pictures do not show up for me, but I can right-click and open in a new tab.
 
I like the basic theory. Pulsed DC is a smart idea. I believe it will improve the etch. 30VAC for the mark should be quite dark.

I don't know that making it battery powered is a plus. Lets face it, an etcher is a bench tool, not a field tool. A 24VAC transformer and a bridge rectifier would be a simpler power source.

What amperage is your system going to deliver?
 
My aim is to be able to deliver 500mA. Last time I tested the draw on an etcher was only around 100mA, so this should be enough. If I'm wrong and it needs more draw, I can add some cooling to the VRM and MOSFETs.

I agree that an etcher isn't a field unit, but I have a fondness for battery powered tools that get used only rarely. There's an added level of protection when you stick to low voltage around liquids.

I have plans to eventually incorporate a titanium anodizer circuit as part of the unit.
 
And add a separate plug for an optional 110 power supply, so that if the battery goes dead you can use it...

I often wish that my cordless dewalt drill had a power supply I could plug into the wall and use it like a normal drill.
 
P.Brewster said:
I suggest you make everything modular and user editable - voltage, pulse duration, etc. Make the power supplies modular from the control unit. It's 2021, not 1981.
Click to expand...
Well, you have a very valid point. I considered variable voltage, but the cost increase didn't justify it. However, if I proceed with the titanium anodizer, then variable voltage will be no additional cost.
 
I am in the market for one. Do you need field testers? I got one of your early forges. I don't have premium. Could you text me at 360.305.6225? I'm not asking for anything free I just really like your stuff. If there is any option to give you business I will do it. I don't forge much but someday I am going to get one of your anvils. It would be so much nicer than my cool old post anvil.
 
You could go with rechargeable 18650 high drain batteries. Lots of people have these in flashlights or other electronic devices. Would save time on engineering a connection for different battery pack types.
 
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