Metal etcher with an H-bridge

[matn1]

Greetings!
I have been learning electronics on the fly, partly from EEVBlog and other sources.
I am also a part time knife maker, where I have had the requirement to etch metal.
This process is normally accomplished with DC 24v at about 1.5A current to remove metal, and then switch to AC to darken the etch. This is done using a piece of felt dipped into an electrolyte, generally salt water. Anyhow: works ok with my lab PSU for DC and then switching to a big block transformer for AC, but then thats not a fun integrated solution is it

SO: I've begun, through trial and error and magic smoke, to design a microcontroller based version of this which would allow me to switch from AC to DC and also alter output voltage. Thus far, I have finished the variable DC voltage part, but am now facing an issue where I would actually like to prevent the circuit from going above 2A output, whether its in DC or AC. By that token, I also want to prevent the system from failing due to a short of the 2 output leads.

I have drawn what I have built in Eagle, and I am attaching a screenshot of my circuit thus far (I have mediocre Eagle skills to this day).

Could anyone comment on what I could do to impose a max current of 2A along with shield this against shorting the leads?
Somehow I dont think controlling current via code would be timely enough as opposed to hardware control. Perhaps that perception is wrong however...

Thanks!

[daveatol]

The LMD1820 has a current sense output, which you can use in conjunction with a comparator (possibly the one in the microcontroller) and reference voltage to trigger the LMD1820 BRAKE line when current is >2A. You'd then want an inductor in series with the etching output to slow the rate of change of the current when the brake is applied/removed (otherwise the current will just oscillate between MAX and 0A).