This is my new red burner. It powers an Optnext hl6545mg diode from a group buy at Photonlexicon using a single rechargeable lithium cell (18650 size) in a modified DX Romisen RC-M4 flashlight. To get current regulation with very low overhead I used a circuit posted by Phenol.
The name "Liberty Torch" comes from my heat-sink. I wanted a good one... Jayrob makes nice heatsinks, but they don't fit my hardware... so I improvised. Rather than replacing the reflector cone with a heatsink, I used coins and washers of various diameters to fill the space inside the reflector. Looking for something that fit exactly for the last/outside layer, I found that a dollar coin is exactly the right size - and I thought Liberty with her torch was appropriate. Here's how it looks:
The various metals in the heat-sink don't conduct heat as well as a solid block of Al would, but they have a much higher heat-absorbing capacity; and the space around and between the washers is filled with heat-sink compound. This thing takes quite a while to heat up, even though I'm driving it with 300mA.
I put the circuit on 2 boards: one replaces the flashlight's original board and doubles as the battery contact holder; the second board has only the output stage and is placed on the backside of where the Cree LED was originally. Surface-mount components were used to keep the size down. The current is adjusted with a tiny 10-K pot (the original circuit called for 20K); it's placed in the center of the board and is adjusted through a hole in the back of the board (via the center of the positive battery spring terminal).
The circuit board came out a bit rough because I heated the etchant, and then got distracted playing with my dog so left the board in too long - there were a lot of pits and rough edges. The photo below shows the bare boards, not yet cut and trimmed. All the rough copper outside the circles is where I used a black marker pen to mask unused areas, to save etchant. The big pads for battery and heatsink contacts on the reverse side of the boards are visible as shadows through the thin etched board.
The boards with all components:
Mounted on the flashlight parts:
Nitpicky component details that vary from Phenol's:
One unfinished piece: I'm going to add an "overdrive" switch to push it up to 400mA. That will be implemented with one of the magnetic reed switches mounted inside the head. Attaching a magnet in the proper spot will connect a resistor in parallel with the reference voltage adjuster.
DanQ
The name "Liberty Torch" comes from my heat-sink. I wanted a good one... Jayrob makes nice heatsinks, but they don't fit my hardware... so I improvised. Rather than replacing the reflector cone with a heatsink, I used coins and washers of various diameters to fill the space inside the reflector. Looking for something that fit exactly for the last/outside layer, I found that a dollar coin is exactly the right size - and I thought Liberty with her torch was appropriate. Here's how it looks:
The various metals in the heat-sink don't conduct heat as well as a solid block of Al would, but they have a much higher heat-absorbing capacity; and the space around and between the washers is filled with heat-sink compound. This thing takes quite a while to heat up, even though I'm driving it with 300mA.
I put the circuit on 2 boards: one replaces the flashlight's original board and doubles as the battery contact holder; the second board has only the output stage and is placed on the backside of where the Cree LED was originally. Surface-mount components were used to keep the size down. The current is adjusted with a tiny 10-K pot (the original circuit called for 20K); it's placed in the center of the board and is adjusted through a hole in the back of the board (via the center of the positive battery spring terminal).
The circuit board came out a bit rough because I heated the etchant, and then got distracted playing with my dog so left the board in too long - there were a lot of pits and rough edges. The photo below shows the bare boards, not yet cut and trimmed. All the rough copper outside the circles is where I used a black marker pen to mask unused areas, to save etchant. The big pads for battery and heatsink contacts on the reverse side of the boards are visible as shadows through the thin etched board.
The boards with all components:
Mounted on the flashlight parts:
Nitpicky component details that vary from Phenol's:
- sense resistor: 3.0 ohm
- dual op-amp: TLC252CPWR in TSSOP-8 package
- P-channel power MOSFET: FDT434P
- voltage reference: little green LED with Vf=2.0V
One unfinished piece: I'm going to add an "overdrive" switch to push it up to 400mA. That will be implemented with one of the magnetic reed switches mounted inside the head. Attaching a magnet in the proper spot will connect a resistor in parallel with the reference voltage adjuster.
DanQ
