Thursday, September 9, 2021

task lighting hack

 Last month, our old microwave died and had to be replaced.  It's an over-the-range vent-hood style, so it has a task light built into the bottom, to illuminate the cooktop below.

 The old unit had two halogen lamps, which I replaced with two much brighter and whiter LED units.

 The new unit came with a great big glass lens over the bulb, but the lamp inside was a single 50 watt halogen unit in a recessed socket making it nearly impossible to use a drop-in LED replacement.

 Worse, they installed a 130V bulb.  They do this to make the bulb last longer, but this is a mistake because it's a halogen lamp, and halogen lamps need to operate at their full, high temperature, to achieve their longest life, because there is a quasi-chemical reaction going on inside.  Plus, using a 130V lamp on 120V results in a more yellowish light, and quite frankly, for food, we want a neutral white light ideally - neither warm nor cool - for food to look its best to the human brain, which is quite picky about the color of food!  I've shown the original and how it looks on the bench...

 Despite their being mounting points for two sockets behind the lens, only one was populated with a bulb, and this is probably because the airflow through that part of the chassis is kinda anemic, and it gets warm now after the light has been on.  With two of them, external parts of the oven would get two hot to touch.

 Gods forbid they should an LED in this day and age which would generate much less heat, or hack their sheet metal a little to allow more airflow in that area of the chassis... price points suck, okay?  I'm sure the engineers involved would have LOVED to do a better job, but they weren't ALLOWED to, by the bean-counters who were ensuring this unit could be sold for $299.99 and not one thin peso more.

 So here's my plan... the second set of pics shows a "COB"* LED panel, epoxied to a heat sink, both of which I found on eBay.

 The heat sink just barely fits into the opening of the glass lens panel that covers the lights, and once inside, there is enough room for it to simply sit there on top of the glass.

 The heat sink is necessary because there is only a small amount of air flow in the area, and the panel would probably overheat; heat is the enemy of all LED products.

 The photos don't do the new light justice, because my phone does auto-exposure, and if I just manually changed it, it wouldn't be a real comparison.  Sorry, it was late and I was too tired (lazy) to get out the real camera and tripod that day.  Although the LED panel consumes only 10 watts vs. the original halogen's 50, it's subjectively (hand-wave, hand-wave) about four or five times brighter.

 Unfortunately, it is NOT a neutral white, and I'm going to replace it when I find one that is.  This was the only panel I could find that filled my needs, and it is decidedly bluish (6000-6500K according to the seller) but the alternative (3000-3500K) seemed too warm.  For neutral whites, you typically want to stay around 4000-4500K.

 OTOH, it was dirt cheap (at the time, when I had any money at all, LOL): - $3.93 - $8.40

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