Thought I'd share my soldering gun LED mod with the CPF crew.
I have an old Weller 140W soldering gun with an old school incandescent lamp. I wanted to upgrade it to an LED. Since a drop in replacement is not possible, I had to put some thought in to how I'd do it.
A drop in replacement is not possible, because the output for the existing lamp is 2V AC. Not high enough voltage to power a typical emitter. So I decided to use a very simple voltage doubler circuit. I used 2 diodes, 2 capacitors, an old Cree emitter, wire, and heat shrink tubing.
Since the guns lamp voltage is fairly low, I used Schottky diodes because they have a low forward voltage compared to the more common silicon diodes. I salvaged the diodes from an old circuit board I had lying around. If you have old boards of your own, and want to see if any diodes are Schottky, use your DMM set to the "diode check" mode. On most DMM's, the diode check mode displays the voltage dropped across the diode. Schottky diodes drop around 0.3V, and standard silicon diodes are 0.7V+
I used a couple of old 470uf 10v caps I had. No crazy calculations on my part, I just dug through what I had, picked caps that had the largest capacitance, and would also easily fit into the handle of the soldering gun.
Wired it all up, and tested it. Works nice. Emitter and base get warm, but not hot. Perfect. Way brighter than the old lamp, and won't burn out all the time.
Used a dremel to make room for the emitter and base.
See pictures in google drive link below for how I put it together, and the schematic.
https://drive.google.com/folderview?id=0B4s2MCSaoBEDMEllNGkyamJWQWc&usp=sharing
I have an old Weller 140W soldering gun with an old school incandescent lamp. I wanted to upgrade it to an LED. Since a drop in replacement is not possible, I had to put some thought in to how I'd do it.
A drop in replacement is not possible, because the output for the existing lamp is 2V AC. Not high enough voltage to power a typical emitter. So I decided to use a very simple voltage doubler circuit. I used 2 diodes, 2 capacitors, an old Cree emitter, wire, and heat shrink tubing.
Since the guns lamp voltage is fairly low, I used Schottky diodes because they have a low forward voltage compared to the more common silicon diodes. I salvaged the diodes from an old circuit board I had lying around. If you have old boards of your own, and want to see if any diodes are Schottky, use your DMM set to the "diode check" mode. On most DMM's, the diode check mode displays the voltage dropped across the diode. Schottky diodes drop around 0.3V, and standard silicon diodes are 0.7V+
I used a couple of old 470uf 10v caps I had. No crazy calculations on my part, I just dug through what I had, picked caps that had the largest capacitance, and would also easily fit into the handle of the soldering gun.
Wired it all up, and tested it. Works nice. Emitter and base get warm, but not hot. Perfect. Way brighter than the old lamp, and won't burn out all the time.
Used a dremel to make room for the emitter and base.
See pictures in google drive link below for how I put it together, and the schematic.
https://drive.google.com/folderview?id=0B4s2MCSaoBEDMEllNGkyamJWQWc&usp=sharing
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