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9 September 2010
Author: Giorgos Lazaridis
A Camping LED Lamp

The victim...

Every year, near the mid-end of September, the Motohappening takes place! People from all Greece come with their motorcycles, and we camp by the beach in a place called "Mourteri". The Motohappening will take place the following week. We have of course gas-lamps and LED flash lights, but one more LED lamp is never useless...

Back to my grandmother...

Many many years ago, my grandmother bought me an electric lamp. It was powered with two AA batteries and had a single 3V conventional lamp. The design was sweet, but the efficiency was awful. So, i put this lamp in the chop-shop for a little update.

 This is the lamp It uses a 3V conventional lamp and 2 size AA batteries. Bad combination.

First, i had to remove some useless parts:

 I removed the entrails... ...and unscrewed the top side. The lamp holder was easily... broken.

And then i made my own lamp holder:

 The new lamp holder is an x-chopstick from a Chinese restaurant.... ...which, i cut-to-size and fit to the base. I will use 8 10mm high brightness LEDs instead of conventional lamps. I glued the LED on the base with hot-glue, which does a very good job All 8 LEDs are in place in pairs... If you look from above, the LEDs have 45o angle

Dimmer or LED selection?

Recently i made a dimmer circuit for LEDs. I began this project with the intention to use this circuit as a dimmer for the lamp. In the meanwhile, another idea came to my mind. There are situation where someone wants light only in one narrow or wide direction, for example 20 or 80 degrees. If you go fishing for example, you need light only on your bate... So, i changed my original idea. Instead, i use a 5 positions rotary switch. The first position, is the off position. The next one, is the low directional light. The next one is the high -or wide- directional light. The 3rd position is the low polar light, which light all around, and the last one is the full brightness, where all LEDs are lit.

I tried to keep the schematic as simple as possible, yet i could not get the combinations needed without the use of diodes. To reduce the voltage drop across the diodes, i use BAT85 Schottky diodes. Here is the schematic diagram:

And the wiring began

According to the schematic, there are 4 pairs of LEDs, and each LED has it's own limiting resistor. The resistors are 47 Ohms.

 These are the 47 Ohms resistors. I will need 8 of them. All the wiring is done on the LED holder. 5 cables will depart from there... ... and through a hole goes in the base of the lamp

Then, i continued the wiring on the switch and the battery holder:

 This is the 5 positions rotary switch that i will use. The battery holder is ripped off from an old coffee shaker! The diodes are soldered directly onto the rotary switch. The wiring is 100% complete!

Some body work on the base...

 The switch's shaft goes through the hole that the old on-off switch used to be... No need of a new hole. With a ton of hotmelt glue, i hope that the switch will stay there... The 4 batteries fits in the base pretty well. The base had an extruded ring, that used to keep the 2 batteries in place... ...the dremel took care of this ring...

LEDs needs of a diffusion filter

Usually, LEDs have a very narrow light beam, about 25o. To spread the light around, a diffusion filter must be used...

 My diffusion filter comes from a durable membrane from a photo-copy machine I cut a strip with the scissors With a 600 sanding paper i sanded the membrane Carefully i glued the strip into a cylinder and placed it around the LEDs. The End.

A final touch

The rotary switch shaft looked ugly...

 I trimmed the shaft shorter with the dremel... And placed this yellow knob... Much better now.

And the result...

 1st positionLow Directional 2nd positionHigh (or wide) Directional 3rd positionLow polar 4th positionHigh polar