Monday, February 07, 2011

flashlight, no headlight, done

It's finally done...

I got hung up on this convoluted project. Stalled, for months. It was the mounting to the head that I couldn't figure out for the longest time.

The project started out simply enough, to build a flashlight patterned off the Rigel design, with the LEDs emitting from the end. Power efficient so to last long and designed around standard batteries so to stop burning through lithium coins. With LEDs of a colour I could explicitly choose.

The pre-planning, the circuit prototyping, sourcing parts, the schematic work, the circuit design, laying out, soldering, all went swimmingly. The deep red LEDs worked great. I found a 9.5 x 6.0 x 2.5 cm project box that would fit the circuitry and carry a 9 volt transistor style battery. Good size and form factor for a hand held unit.

Things turned or shifted when my hacked red LED clip light broke and that I wanted a replacement. Not just another baseball clip light (converted to red). Not a new head lamp with a red LED (like the MEC I had given Mom; even though her uses AAAs). Perhaps my custom flashlight idea could be used. But it would have to be wearable, to keep hands free, of course. But therein lay the trap.

I started going down this path of trying to build a light that would mount in an equivalent way, clip to the bill of a cap, or perhaps mount like my old MEC head lamp with stretchy bands around the side and top of the head. I tried to figure out a way to get the bulky plastic box to sit atop the bill of a cap or rest against my forehead. I actually found a curved piece of plastic that I considered as a forehead contact point. But then the whole layout of the project box was off with the LEDs in the end. I muddled over my old MEC head lamp, trying to figure out if I could fit the project box to the mount. Given the age of the MEC light, new straps were needed. That presented a new stumbling block of where to find wide elastic straps. I just did not like where things were going. Onto the back burner again.

I think it was as I was searching for little red LED dongle light things [ed: new link] that could be attached to a coat lapel or zipper when I stumbled across the Nite Ize company and their flashlight holding headband. Brilliant idea. Looks like a great product. I think I even found that Bass Pro carried it. So I made a note to check it out.

But that started the wheels turning. If I could make my own headband, perhaps I could affix another strap, perpendicular to the headband, and tie around the project box. And that meant I wouldn't have to reconfigure the circuitry and LEDs. Looked like I was going to be firing up the sewing machine soon.

I think that's what caught my eye about the Velcro Velstretch bands I found at the hardware store. They were the right length for a headband. Better still, they were stretchy (while the Nite Ize product webbing is not elastic). I felt that something that could be at some slight tension would be better. The other interesting tidbit about the Velstretch bands is that entire exterior of the band is loop material. This allows for infinite adjustment. And that would later give me another idea...

Today, not sure why, cloudy skies perhaps, needing a distraction, I decided to finish the project box assembly.

With the new hacksaw, I cut the circuit board to fit the internal guides in the project box. A bit of sanding made for a perfect fit.

I stared at a couple of small switches I had selected for possible use as the main on/off control. The round switch with red toggle was attractive but way too big. It looked like the tiny black toggle would be the way to go. But as I checked fitment, I rejected it as well. Still too large. I looked in the parts bin but didn't find any smaller switches. Whoa. Hold on. Back up.

I picked up a small circuit board salvaged from an old CLA car power adapter. It had a voltage selector switch. It was very small but with robust legs. Ha! I could mount this right to the circuit board, accessible in the same direction or orientation as the rheostat brightness control. Much better. I desoldered the black switch for the CLA board. I routed the power switch leads to the edge of my circuit board and made the "new" switch leapfrog them. It was perfect.

I took the side of a clear plastic box and made a lens. I cut some holes for the power switch and brightness wheel. Bit of trimming was necessary to get everything to line up and avoid collisions.

From another project I grabbed a rubber grommet, slotted it, and fit it at the rear of the PCB to prevent the board from moving backwards as the switch and dial are used.

Cut the deep red LED leads to allow the 5mm domes to sit behind the clear lens.

Cut back the circuit board power lines, soldered the 9v leads, and heated the shrink wraps. Looped the power cords around one of the project box screw posts as an anchor and snapped everything together. Installed the two long screws.

And so after many months, the deep red LED flashlight, inspired by the Rigel, was finally done. Installed a fresh 9v battery and took it for a test drive in the dark bedroom. It was fantastic. Lots of light, dimmable, great colour.

Now, the final step was to see if it could replace the damaged clip light.

While in the bedroom, I hauled astronomy box γ down from the shelf and removed the Ziploc bag with Velcro hook and loop pieces. I found a self-adhesive 5cm square piece of hook already cut. Perfect. I attached it to the "back" of the project, same side as the battery compartment.

At last, I put the Velstretch band around my head. Set the tension so snug, but not too tight. Turned on the deep red light. Aimed it at a piece of paper in front of me. Then slapped the flashlight it to the head band. Amazing.

Added a eyehook to which I attached a lanyard. Now it can be worn around one's neck too. And when in head band mode, wearing the lanyard means it is tethered, which should avoid it bouncing off the ground...

Without specifically intending it, I suddenly realised I had created a far superior solution. The flashlight can be used normally, that is as a hand held unit. When used with the head band, it is infinitely adjustable. Unlikely the Nite Ize band, I can tilt or pitch the flash light, allowing me to keep my head and neck at a comfortable angle. Can be worn directly or over any hat.

I'm so happy with the finished result!


JayOutWest said...

Nicely done and described! Are you still using it?

bla said...

I am. It works very well.