Halogen lamp hack... - Page 1
Forum section: electronics / projects

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: December 22, 2011, 06:25:02 pm
content: So while i was in Christmas shopping i seen a sale on small cute halogen desk lamps. I took one since they were so cheap the 12 VAC transformer inside would cost 2 times more.After bringing it home i knew the 20 W halogen lamp does not give any respectable light so i disassembled the reflector housing. After digging in my trash bin i found a small LED soldered to its small heatsink. I filled the reflector with thermal epoxy and glued the diode hoping it will provide enough heatsinking all together with metal reflector (it does).I mounted the LED permanently because i don't plan to use this product longer than the expectable life of LED.I clipped 2 leads from 1N4007 diodes and used it to connect the power to the LED from the socket of halogen light bulb.Since the halogen bulbs work nice on AC the manufacturer did not include a rectifier and capacitor (its not needed). I clipped the wires close to socket and soldered a full wave rectifier, capacitor and current limiting resistor close to the socket. Then i soldered the original leads back and applied little bit of liquid tape where i consider the clearance was to small.The pics were taken in dark room and same shutter settings to show the difference better. However the halogen looks brighter on photos than it really is.It looks like its an original product, and the light output can be compared in photos. Lamp works nicely, LED is at nice temperature and does not overheat.

author: Simon
author_rank: Unknown
timestamp: December 22, 2011, 07:37:17 pm
content: I have a few halogen lamps like that I will get around to doing this to one day. What sort of agle does the led have ? is it difused enough ?

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: December 23, 2011, 05:10:02 am
content: Quote from: Simon on December 22, 2011, 07:37:17 pmDon't ask me about any data on the LED. One company that works with us sent us a batch of presents in a form of battery powered flashlights (cheap Chinese crap) which did not work at all because its made in segments of aluminum and they don't pass electrically unless you wiggle and squeegee the flashlight.So i just harvested out the leds.Regarding the diffusion i can say its perfect. There is no hot spot on illuminated surface, its quite nice.

author: RJSC
author_rank: Regular Contributor
timestamp: December 27, 2011, 01:22:57 am
content: Nice of you to post it!I have done the same last year with my 10 year old but still looking good desktop halogen lamp.I pulled the LED out of a 9€ 12V GU10 led featuring a single 3W LED and it even had a switching current supply to drive the LED. The metal reflector was also a good heatsink.Only if the LED color temperature would be warmer (more yellow component) it would be nince, dince it is mainly used during the night, and the grater component of blue in daylight delays the production of sleep hormones on the brian causing insomnia on sensitive people like me.For the ones thinking they might also be sensitive to blue light, I'm using a program on the computer that automatically reduces the color temperature at night and I started to sleep better.They are:- F.lux (Windows),http://stereopsis.com/flux/- RedShift (Linux),http://jonls.dk/redshift/Even if your sleep cycle is not affected by high levels of blue light at night, it might just help to reduce the strain on your eyes at night.

author: Simon
author_rank: Unknown
timestamp: December 27, 2011, 09:07:00 am
content: haha I'mthe exact oposite, I got a 5500K CFL and painted my computer room walls white to try and stave of tiredness. I have those shitty 2700K CFL's. I'm glad to hear they are actually of use sometimes

author: amyk
author_rank: Super Contributor
timestamp: December 27, 2011, 09:45:05 am
content: There is 12VAC across the two metal rods that support the head.Not enough to give you a shock but enough to make some sparks if something metal shorts across them, and possibly kill the transformer.Retarded design, in my opinon.

author: Simon
author_rank: Unknown
timestamp: December 27, 2011, 09:54:42 am
content: yea i could never work that one out, talk about health and safety, we major over stupid things and minor on ones that really matter

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: December 27, 2011, 10:28:24 am
content: Quote from: amyk on December 27, 2011, 09:45:05 amWell the transformer will surely not die if that happens unless the short circuit lasts quite a long time. Since the lamp is above working area there is not much chance of it at first. But if desired you could easily take a separate cable and run it to the lamp head.

author: Simon
author_rank: Unknown
timestamp: December 27, 2011, 10:30:13 am
content: try having one of those in your lab, you'd soon be fighting to make sure that it don't get shorted, I am ever mindful of where i put mine and what it is near

author: Unknown
author_rank: Unknown
timestamp: December 27, 2011, 10:35:01 am
content: Quote from: Simon on December 27, 2011, 10:30:13 amSmart bloke, a few minutes, a bit of clear heatshrink, hot air and the problem is gone!

author: Simon
author_rank: Unknown
timestamp: December 27, 2011, 10:37:18 am
content: well that reduces it's functionality of being able to vary the height. I don't worry too much about it but just bear in mind where I'm putting it and what I put near it, they are very good for lab work as they are nice and small and you can get them as close as need be

author: hacklordsniper
author_rank: Frequent Contributor
timestamp: December 27, 2011, 11:24:42 am
content: The most simple would still be to take a thin cable and run it arround antenna to the head

author: Simon
author_rank: Unknown
timestamp: December 27, 2011, 12:21:23 pm
content: Quote from: hacklordsniper on December 27, 2011, 11:24:42 amyes that would be the best way if one was paranoid

author: RJSC
author_rank: Regular Contributor
timestamp: December 27, 2011, 02:09:27 pm
content: If someone is going to run a wire alongside the antenna, I recommend to drill the top and bottom and run the wire inside it.The only problem is that sometimes the top section of the antennas is a solid rod, but some are all made of tubes.

author: Simon
author_rank: Unknown
timestamp: December 27, 2011, 03:35:22 pm
content: what about just using a spring wire like on phones so that it lengthens as required - or will it end up permanently long if kept extended

author: SeanB
author_rank: Super Contributor
timestamp: January 10, 2012, 07:39:28 pm
content: I did the same, using a 1W Stanley LED lamp. Used an old LGA775 heatsink without the fan as the heatsink, tapped 2 M3 holes for the screws. Runs from a slightly modified Nokia charger, with a 4R7 resistor as current limiting. Had to replace the supply caps on the charger ( bulging and near to bang) primary and secondary, with salvaged old but good low ESR capacitors. Added a steel block in the bottom to make it stable, and it works well. Not as bright as the original 12V 50W GU5.3 halogen, but as bright as a 20W halogen. Just a lot cooler, now it is a lamp and not a heater, and the plastic parts no longer deform from heat. The heatsink is a little overlarge, as the die is only 5C or so above ambient. Now a nice cool running Anglepoise style desk lamp.I am looking to do the same to another lamp, with the exposed wiring bars like the OP, using some LED retrofit lamps that are supposed to replace a halogen. That lamp already has a replacement toroidal transformer in it, the old one went crispy from overheating when somebody put a 50W lamp in it instead of a 35W lamp. Old core made a very nice current transformer core though.