Posts Tagged ‘modification’
As I wrote in my blog post a few days ago, I got the intensity down for night vision for my red flashlight. But I wasn’t quite happy with the level and wanted to reduce it even more. To do that I had to unsolder 6 of the 8 AMC7135 350 mA constant current ICs on the PCB of the AMC7135*8 2800mA 4-Group 5-Mode Circuit Board.
These constant current chips are all run in parallel with the VDD input for control. The 8-pin Atmel ATtiny13A chip controls all VDD inputs in parallel from its pin 6. When the VDD pin is low there will be now light. I haven’t measured this, but I am assuming that this pin is pulsed in order to reduce current down from the maximum.
- 8 chips: 2,8 A, 0.83 A, 0.14 A
- 4 chips: 1,4A, 0.45 A, 0.08 A
- 2 chips: 700 mA, 225 mA, 42 mA
This scales as expected with the number of 350 mA chips and the 100%, 30%, and 5% settings of the controller. Now only Q1 and Q3 remain, and Q2, Q4-8 have been desoldered.
One could have obtained en even more battery-friendly version if somehow the original controller could have been modified. The step-down circuit is quite standard with an inductor, a Shottky diode (SS14), and a controller chip of unknown origin. But it seems to me that if R23 of value R250 (0.25 ohm) was increased, output current would probably go down.
As it is I am much more happy with the intensity of the settings I have now. It will be a good companion night light which will preserve night vision well when used with a telescope.
I got this red LED flashlight as a Christmas present. But unfortunately the intensity was way too high for what I intended to use it for. A soft red light preserves your night vision, and is ideal for use with a telescope in the dark as was my intention. But if the intensity was as high as before the modification, night vision would suffer.
I then found this YouTube video describing how the controller circuit board could be replaced by one with more functions. As recommended I therefore ordered an AMC7135*8 2800mA 4-Group 5-Mode Circuit Board with 8 AMC7135 current regulators in parallel. The image shows the the original circuit board as connected before the modification in the front in the image and the new one behind it.
- 3-mode: Lo (5%) – Hi (100%) – Strobe
- 3-mode: Lo (5%) – Mid (30%) – Hi (100%)
- 2-mode: Lo (10%) – Hi (100%)
- 5-mode: Lo (5%) – Mid (30%) – Hi (100%) – Strobe – SOS