Monday, March 1, 2010

Dynamo Lighting: Control Box

More lighting shenanigans. Working on the prototype of the control and power distribution system; "simple" and "cheap" are the order of the day.

Here's the glory. Lower terminals to the left with red leads to the left are dynamo hub inputs; push-button SPST(on-off) switch with handlebar mount improvised from taillight seat post mount is to upper left; and the project box lid with the breakouts for one to three lights is in the upper right.

Here's the board. I got jiggy with the label maker, since I can never remember which wire of which color goes where. (Although obscured, there are labels for HUB and SWITCH at the top.)
Components(from top down) consist of a set of terminal blocks for wire attachment, a set of four Schottky diodes for a full bridge rectifier, and a big ol' 4700uF capacitor to smooth out the low-speed flickers. All of this terminates in the positive and negative terminal blocks at the bottom, from whence the magic juice that makes the lights go shall pour.

The dirty little secret on the bottom...a veritable rats nest of wire. Hey, it's a prototype...

The switch. I hope not to bang my knee on that thing, when it's mounted on the bars; that would sting a bit otherwise.

The underside of the lid (traditional dirt-cheap Radio Shack project box); this will let me wire up to three lights in series, all controlled by the single switch.

Most of this went together fairly painlessly. The handlebar mount for the switch was probably the most difficult part. I scavenged through the official "Random Mounting Bits" box, and eventually found a busted taillight with a seat post mount that looked promising. Removed the light, and carefully drilled the remaining tab out on the drill press until the unthreaded shaft of the switch could pressure-fit inside; then, did a little impromptu thread tapping of the hole by carefully twisting the switch until its threads cut into the mounting hole.

Now that I've built this thing, I realize that I have no idea how well the screw terminals will withstand vibration. It'll be a bit annoying if the wires pop loose on a regular basis. If so, I can certainly do a little roadside repair by twisting wires together directly, and garnishing with a length or two of electrical tape; hopefully, it will not come to that.

Looks like someone forgot to check the clearance.

It appears that I will not be using the existing standoffs molded into the project box. No, nay, instead I shall be performing some precision X-Acto surgery to remove said molded standoffs and lower the board into the depths, so that the damn lid may actually close.

You can see some of the casualties off to the left. I'll re-glue the orphaned terminal later.

Well, after a bit of work with coping saw, file, utility knife, and profanity in three languages, I got the box to close. I suspect that I may need to replace the capacitor, as it now has a significant dent where one of the terminals was pressed with unwarranted vigor.