555 Contest Entry – PCB Etching Controller – Schematics

Trying to get the circuits put together on the protoboards. It has been quite an undertaking so far, yet still have so much to do. All schematics are in PDF format derived from Kicad. I just hope they come out alright on the site here.

I will be posting a video as soon as I get the circuit completed which will HOPEFULLY be by the deadline of the contest. I’d hate to have an incomplete project to demo.

This design is a control scheme for a PCB etching solution that utilizes Ammonium/Sodium Persulphate etchant, mixed with water within the system itself. There are 3 main “tanks” not including the spray etching tank. The Mix Tank mixes the crystals with water. Then the mix tank dumps into the Recirc Tank, which monitors level probes for consistent spray pump supply to the etching tank. Then the waste tank periodically dumps a portion of the recirc tank to keep the etchant somewhat fresh. When the Mixer Tank gets low from filling the recirc tank, it goes into a Mixer Cycle, making a fresh batch of etchant.

Everything in this design is interlocked to another part of it. This gives the desired operation of the design. The Grand Master circuit is the “Master Arm” control. From there you can follow all the I/O tags of each schematic to see how it is all interlocked. The Motor-PWMs circuit is actually used three times based on where it is used. The interlock on the left side of the schem shows the three different options at the OR gate.

I hope to get a Google SketchUp drawing done to show the intended apparatus for this circuit, but if not, I will submit a snapshot of my hand drawing of the setup.

Etch Master and Timer

Recirc and Waste Tank Levels

Waste Valve Timer

Recirc Outlet (Waste Valve) Control

Youtube Video

Interface Layout to go with the Video