2x12mm, 4x8mm M3 screws with washers and nuts
4x12mm flat head M4 screws, washers and nuts
M3 grub screw with M3 nut
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1
Bearing
3x8x3 bearing
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2
Electronic components
45mm Slider with 35mm travel
See Schematic for other components. Resistors and Capacitors are 0805
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1
Hand tools and fabrication machines
3D Printer (generic)
Drill / Driver, Cordless
Story
I make a lot of my own printed circuit boards and etching was always a bit of a chore since you really need to keep the acid moving over the copper. My left arm muscle is now testament to the number of boards I have made over the years by manually agitating the acid bath.
I was watching a agitator built by TechBuilder on YouTube and decided I needed one.
Demonstration
Demonstration of my PCB agitator
Hardware
The unit is built around a Jiffy Box (157x95x53mm). The motor is a 100RPM geared 12V brushless motor from eBay. The hinge was one I had found in my toolbox (I think I got from Bunnings but can't really remember. Anyway it's a Black Nylon Hinge (48mm length x 48mm (open) x 9mm thick). The 3D printed Cam is held on to the motor shaft using a M3 grub screw and M3 nut. The bar incorporates two 3x8x3 bearings to reduce the friction.
100RPM geared 12V brushless motor
Cam, Bar, and Hinge
Electronics
The motor speed is controlled using a PWM signal generated from a 555 timer via a N-Channel MOSFET. I used the same circuit that I designed for my Ender 5 light bar. Instead of driving an array of LEDs, it drives the motor. The other side of the motor is connected to VCC or 12V. You need to add a diode across the motor to stop back EMF from the motor destroying the MOSFET. (Anode to the MOSFET, Cathode to VCC). Also you need to replace R2 with a 0 ohm resistor.
Schematic of motor controller
The PCB was designed to fit a 45mm slide potentiometer with a 35mm travel. I used surface mount components because that what I had around the workshop.
The PCB is designed to be solder to a 45mm slide potentiometer.
Assembled controller mounted to side of box (Note diode soldered across connections to motor)
Finishing up
I used a DC Panel connector and a 12V 2A power brick to provide the power.
DC Panel connector and final wiring
To secure the tray that holds the acid, I decided to use fridge magnets. Trade people tend to leave a lot of these in letterboxes here in Sydney so now I finally have a use for them. Glue some to the top plate of the agitator and to the bottom of your etching trays.
Fridge magnets make a great way to attach/deattach the etching trays
I found its best to agitate along the longest axis of the tray. To much liquid when the top is over to one side will place a lot of load on the motor especially when that liquid is further away from the fulcrum. You don't want a lot of movement, just enough to have the acid slowly go back and forth across the copper.
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