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14 Dec 2014 : Adafruit Backlights as Nightlights #
Yesterday I spent a fun and enlightening day at DoESLiverpool for their monthly Maker Day. It was my first time, and I'm really glad I went (if you live near Liverpool and fancy spending the day building stuff, I recommend it). I got loads of help from the other makers there, and at the end of the day I'd built a software-controllable blinking light and gained a new-found confidence for soldering (not bad for someone who's spent the last twenty years finding excuses to avoid using a soldering iron). Thanks JR, Jackie, Doris, Dan and everyone else I met on the day! Here's the little adafruit Trinket-controlled light (click to embiggen):

Adafruit Trinket with a backlight module attached, alongside a tealight

The light itself is an adafruit Backlight Module, an LED encased in acrylic that gives a nice consistent light across the surface. In the photos it looks pretty bright, and Molex1701 asked whether it'd be any good for a nightlight. Thanks for the question!

The only thing is I know nothing about lights and lumens and wouldn't trust my own judgement when wandering around in the semi-dark. So to answer the question I thought it'd be easiest to take a few photos. The only room in the flat where we get total darkness during the day is the bathroom, so I stuck the adafruit in the bath along with some helpful gubbins for reference (ruler, rubber duck, copy of Private Eye) and took some photos. As well as the backlight module, there are also some photos with the full light and a standard tealight (like in the photo above) for comparison. I reckon tealights must be a pretty universal standard for photon output levels.

These firsts three below (also clickable) show the same shot in different lighting conditions from afar. Respectively they're the main bathroom light, the backlight module, and a tealight.

Bathtub with standard florescent bulb from above
Bathtub with backlight light inside
Bathtub with tealight light inside

Here are two close-up shots with backlight and tealight respectively.

Bathtub close-up with backlight light inside
Bathtub close-up with tealight light inside

As you can see from the results, the backlight isn't as bright as a tealight. Whether it'd be bright enough to use as a nightlight is harder to judge, but my inclination is to say it probably isn't. Maybe if you ran a couple of them side-to-side they'd work better. It's also worth noting the backlight module is somewhat directional. There is light seepage from the back of the stick, but most of the light comes out from one side and things are brighter when in line with it.

It may also be worth saying something about power output. Yesterday JR, Doris and I measured the current going through it. The backlight was set up with 3.3V and drew 10 mA of current. The battery I'm using is a 150mAh Lithium Ion polymer battery, so I'm guessing the backlight should run for around 15 hours (??) on a single charge. Add in the power needed for the trinket and a pinch of reality salt and it's probably much less. Last night it ran from 8pm through to some time between 4am and 10am (it cut out while I was asleep), so that's between 8-14 hours.

If you do end up building a nightlight from some of these Molex1701, please do share!


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