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Workbook » Blog Archive » Aleph Light Engine Build Notes

Aleph Light Engine Build Notes


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Required parts:

  • Aleph Light Engine Kit (Ecan, Escrew, and emitter board)
  • Badboy or Downboy Power Converter Board
  • Luxeon Emitter
  • Hookup Wire (0.75″ red, 0.75″ black, 1″ bare solid ground wire)

Parts for Project

Required tools:

  • Soldering Iron
  • Solder
  • Thermal Epoxy
  • Hobby Knife
  • Super Glue

Helpful:

  • Vise
  • Flat-blade Precision Screwdriver
  • Needlenose Pliers
  • Tweezers
  • Nippers
  • Needle Files
  • Non-adhesive Thermal Grease

Prep Work

Some runs of Badboy and Downboy boards have had excess copper protruding from the edge that can cause shorts to ground, which usually destroys the board. If any copper bits stick out around the edge, file them down until flush with the rest of the PC board, then coat the entire edge with non-metalic nail polish (an insulator).

Copper Edge Defects Edge Coated with Nail Polish

Prepare the emitter board and Escrew. I use a square needle file to ream out the wire clearance holes to make them just a bit bigger. Make sure the board fits cleanly in the top of the Escrew, and file around the edges if necessary. Super glue the emitter board to the Escrew, making sure the holes in the board line up with the holes in the Escrew.

Emitter Board Glued to Escrew

Let the glue set. Position the emitter in the center of the board. The tabs on the side of the emitter indicate which side is the cathode (-) and which is the anode (+). The tab with the hole in it indicates the anode, the tab with the notch is the cathode. If you’re using a Luxeon that was removed from a star, the anode side with have a tab that is slightly longer than the cathode side. You may have to trim a bit off of the “feet” of the emitter’s leads so that they don’t touch the inside wall of the Escrew. I generally clip about half of this foot off. Once you get all of this straight, put a dab of thermal grease (or thermal epoxy) on the Escrew in the open hole in the emitter board, press the emitter into position, and solder the Luxeon leads to the emitter board pads.

Luxeon Soldered to Escrew

The Escrew portion of the Light Engine is now complete.

Wiring

Cut the wires for the emitter. Each should be about 0.75″ with 0.1″ stripped from one end of each for the converter board and 0.2″ on the other end of each for the emitter. Tin the wires on both ends. Now is a good time to make sure the wires are long enough. Place them in the appropriate holes on the board, place the board in the Ecan, then test-fit the assembly into the head and check for adequate length.

To solder the lead wires to the driver board, simply place them in the appropriate holes on the top side of the board (the side with the components), hold them in place (with helping hands or self-closing tweezers if possible), and briefly apply the soldering iron to the bottom side of the board (the bare side). Just a quick touch with the iron will melt the tinned solder and secure the wire to the hole. See the wiring diagram [qv] for your converter to identify the appropriate holes. The red wire goes in the “LED+” or “LED anode” hole and the black wire goes in the “LED-” or “LED cathode” hole.

Cut about 1 inch of wire and strip all the insulation for the ground. Using a file, grind a groove on the top lip of the Ecan. Make it deep enough to hold the ground wire. While you have the file, grind a few notches around the top inside lip of the Ecan, these will help the epoxy grip the Ecan later when we pot the assembly. Place the ground wire in the groove with the bulk of the length on the inside of the Ecan. Heat the joint between the wire and Ecan and apply solder to the joint. It will take a while to heat the wire as the entire Ecan is acting as a heat sink. Crank up the temperature on your iron if possible. Once the joint heats up enough, the solder will flow. Fill the entire groove with solder. Once you have a good joint, trim the wire on the outside and file it down until it’s flush with the Ecan, both on the outside edge and on the top.

Now glue the converter board into the bottom of the Ecan. You need to make sure the ground wire will line up with the milled slot on the bottom of the Escrew when you thread the lead wires through the Escrew holes. Its a good idea to test fit the Ecan and Escrew together before gluing anything together. Just put a thin line of regular superglue on the inside lip of the Ecan and drop the board in. Don’t use too much glue, you only need to hold the board down for a bit until you goop in the real potting material. Let this set up for 15 minutes or so. Once it’s cured a bit, use needle-nose pliers to thread the ground wire through the ground hole on the converter. Solder from the bottom and trim with flush cutters.

Now is a good time to add a solder blob to the battery contact (the large circular pad in the middle of the bottom of the converter board. Just heat the pad and feed solder onto it until you have a nice round dome.

Completed Ecan and Escrew Assemblies

Power Test

Test the emitter and circuit. First, test the emitter itself by applying 3v, using a 2xAA battery holder direct drive if you don’t have a bench power supply. Then test the converter assembly. A simple way to do this is to hold the Ecan (with the converter still glued in) in a vise with the lead wires paralell to the ground, then press an old beat up Luxeon to the ends of the leads (if you don’t have a scrap emitter it’s fine to use your “production” emitter). Then, power the circuit with a Radio Shack AA battery holder (just touch the red wire to the battery contact and the black wire to the edge of the Ecan). If it lights up, you’re good to go. If you’re using a Badboy converter, use 2xAA for 3 watt emitters and 4xAA for 5 watt emitters. If you’re using a Downboy, you should use a 4xAA setup for 3 watt emitters, or a 6xAA setup for 5 watt emitters.

Fitting Test

Test-fit the Ecan to the Escrew. Make sure the two parts fit snugly all the way around, and that the ground wire rests inside the milled slot on the bottom of the Escrew. Fold the wires down to make sure they are long enough to reach the solder pads. Check the emitter’s leads to make sure they aren’t going to short against the inside lip of the Escrew. Take everything apart (trim the leads or wires if needed) and re-test.

Potting

Mix up the potting bog. Arctic Alumina is the standard, but any non-conductive thermal epoxy should work (i.e. you want it to conduct heat, but not electricity). You have to keep moving from here on so the epoxy doesn’t get too thick on you. Don’t rush, but don’t play around. Just stay focused and you’ll be OK.

About two pea-sized drops of each component should be plenty. Mix the components together, then begin potting the Ecan. You don’t need to fill the Ecan up, just use enough to coat the bottom. Make sure it covers to the edge of the board and up the side of the Ecan wall, as that is what will keep the driver in place. Also try to get the wire joints completely surronded by goop, since these will be the weakest physical points in your assembly and the epoxy will immobilize the joints. Be careful not to get epoxy on the other end of the wires (the end that will be hooked up to the emitter).

Put a little bit of epoxy inside the milled slot on the bottom of the Escrew. Not too much. Just enough to dip inside the Ecan and keep the two parts from torquing apart from each other. Dab a little excess epoxy around the inner top lip of the Ecan to bond to the Escrew.

Potting the Light Engine Ecan and Escrew Joined Together

Join the Ecan and Escrew assemblies. Fold the wires down to the correct solder pads (black to - and red to +) and squeeze the parts together. A vise with rubber-lined jaws is great for this. Let the epoxy cure for at least thirty minutes, preferably more.

Final Hookup

Using a small flat-bladed screwdriver, push the wire down onto the emitter lead on top of the solder pad, and briefly apply heat from the soldering iron. If you tinned the wires well, the solder will flow and bind the wire and emitter lead to the solder pad. Repeat for the other wire/lead. You want to keep these joints as tidy as possible so they don’t short against the reflector. All exposed metal should be below the top edge of the Escrew, with only the dome of the Luxeon poking above. Test the Light Engine. Assuming it works, cover the two joints with nail polish and let that dry.

Completed Light Engine with Aleph-1 Head

Install the light engine in an Aleph head. Screw it all the way in, until it is snug against the reflector. Remove the Light Engine and check the nail polish. Repeat a few times. If none of the polish has rubbed off, you’re in good shape. If the reflector is rubbing the polish off, you need to remove the polish, de-solder the leads, and try to reconnect everything using less solder. Once you’ve got a tidy joint that doesn’t touch the reflector, put everything together and test it out.

Light Engine Installed in Aleph-1 Head

Congratulations

That’s it. Your Light Engine is now ready for use. Be sure to use the Light Engine only with voltages suitable for your power converter and emitter combinations. For one or three watt emitters with a Badboy converter, 3v is recommended. For one or three watt emitters with a Downboy converter, anything from 4.5v-12v is fine. For five watt emitters with a Badboy, 6v is optimal, but 3v will work at slightly reduced brightness. For five watt emitters with a Downboy, 9-16 volts is fine. Do not exceed recommended voltages for Badboy converters, as input voltage above the emitter’s forward voltage will damage the converter. When using Downboy converters, input voltages below the optimal range will not damage the circuit, and will simply place the circuit in direct-drive mode.

Enjoy your new Light Engine!

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