Second prototype !

A project log for Darkroom lamp for wet plate collodion

Orange safelight for field photography

pierre-loup-mPierre-Loup M. 04/26/2019 at 08:430 Comments

For the initial design it was intended to use a side push button, coupled with a D-flip-flop to turn the power on and off. The idea was that when you are working in the dark, and want to turn the light on or off, you don't have to wonder which way to move a button; you just push, and it toggles.
Sadly, I couldn't come to have the flip-flop work. After checking the board maybe twenty times, after having checked for shorts, after having changed the components around, suppress or add capacitors, resistors, nothing. On some boards it was always on, on other always off. After having look around the Internet, I discovered that this flip-flop needs a fast switching on the clock line. So I even tested it with an Arduino giving the clock edge. Nothing. I've also tried to disconnect the set and reset pins of the IC, that are active low and can be tied to VCC. Here it almost worked. Almost. After a few days I gave up.

So, new prototype, with a side sliding switch instead of the push button + flip-flop. The BOM is smaller, the cost as well, and I've design a new enclosure and slide button that will be easy to use. A batch of boards has been ordered, assembled, and this time everything is ok.

Next step is building the enclosure. 3D printer is now running to print the bare parts that will soon become the master for the mold, and the silicone and PU resin have been delivered yesterday...

Oh, and : someone asked about the color used, and I realized yellow led seems to be outside the collodion sensivity. So I'll give a try to yellow. If the collodion agrees, it should be even more comfortable than orange !