Digitally-controllable AC light dimmer assembled with solder paste reflow with toaster oven

This light dimmer, with 3D printable or CNC routable case design, makes it safe for you to control dim or switch AC powered devices with safe low-voltage DC signals from a small computer such as an Arduino, Raspberry Pi, BeagleBone Black, etc. And if that computer has a USB, serial, Bluetooth, WiFi, or other interface, then so do your lights. (You could also control a universal motor such as in a typical electric corded drill.)

I downloaded the printed circuit board layout files (Gerber files, analogous to PDF) of the Inmojo Digital Dimmer v.2 from here.

I uploaded these to OSH Park for fabrication. I got six bare (blank) PCBs for $24.70 shipped. Shipping is free, so I could have ordered 3 for just $12.35.

Since OSH Park offers only 1-mil copper and this design is intended for 105um or 4-mil copper, the dimmer can carry only one-fourth of the rated 10A current, unless one were to add a jumper wire of heavier gauge parallel to the deficient trace. In this case, the capacity is about 2.5 amps. That's enough to run over 250W of light bulbs, which is over 25 if they are the LED kind that draws under 10W each. (Some LED bulbs work very well on dimmers, but check first to make sure. Cree ones work like this"60W equivalent" very well thanks to a good "power factor correction" circuit that makes them dim almost identically to an incandescent.)

I bought components to assemble several of these. I ordered from DigiKey and my bill of materials is here.

I used an OpenSCAD parametric script to generate a case.

So far I've assembled two dimmers and they work. I'm open to selling assembled dimmers, kits. or blank PCBs. I may also design a version of the PCB which can carry the full originally intended current on 1-mil copper such as is available least expensively from fab houses such as OSH Park.

These dimmers can be used for dimming lights. An Arduino, Teensy, other microcontroller, Raspberry Pi, or other small computer can be used to control them. They emit low voltage (0-5V) DC signals that are safe. One signal indicates zero-crossing. It should trigger an interrupt in the microcontroller. The microcontroller needs to switch an output after a certain delay, depending on whether your AC power is 60Hz (as in the US) or 50Hz. Dimmer source code for Arduino can be found here.

This was my first solder paste reflow project. I used the simple Black & Decker toaster oven that I took to Xerocraft and keep on a shelf in the north loft. I used it manually, without a thermometer or thermostat.

The solder paste I used was "MG Chemicals 4860P-35G Solder Paste, Sn63/Pb37, No Clean," ordered from Amazon. This came with one applicator tip with a fairly big cylindrical bore. I got additional, finer tips from Connor and from David Forbes. This style of tips is called "Luer-Lok" tips. They thread on, with one big thread. I liked the conical-bore, all-plastic tips best.

Eliott Electronics is local and generally I prefer to buy from them when I can. They carry another brand of solder paste that doesn't use Luer-Lok tips. For this reason, I don't recommend it, if you think you might like a selection of different tips.

Other case option: laser-cut box generated from box maker script:

Inkscape extension: http://hackaday.com/2012/07/26/box-maker-extension-for-inkscape/

Web app to PDF: http://boxmaker.connectionlab.org/

Parametric 3D solid modeler: http://www.openscad.org/