It was time to upgrade the interior lights in my 2004 Volvo. I got some lamps from Ebay specified as 42 mm LED Festoon, 80-85 lm, 12V. As many others have experienced also, they kept on glowing faintly after the door was closed. But when the ignition was turned off the lamps were completely off also, so there was no danger of draining the battery. Still this is not the way one expects lamps to behave.
One can get more expensive LED lamps which avoid this faint glow, "Canbus error free" seems to be the way to specify this. But mine were of the plain type, and the problem seems to be the leakage current in the FET switches that turn the lights on and off. It is tiny, but enough to give a voltage large enough to turn the LEDs on. An additional resistor load will lower the voltage below that threshold.
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 no light. I haven't measured this, but I am assuming that this pin is pulsed in order to reduce current down from the maximum.
My measurements for the High, Medium, and Low settings are:
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 anyway.
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 original circuit board as connected before the modification in the front in the image and the new one behind it.
The new board gave me the choice of one of 4-groups:
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
IKEA Oleby automatic wardrobe light with passive
infrared sensor upper right and four LEDs in the center.
Passive Infrared (PIR) detectors have the bad habit of being sensitive to radio frequency (RF) radiation. This can be a nuisance for neighbors of radio amateurs. But we can use this property to our advantage as this makes them suitable for transmit indicators next to a feedline.
The IKEA motion activated LED sensor light, which one can get for a few dollars or euros, turns out to be quite simple to hack for this purpose. You can only buy them in pairs so the other one can be put to use in the darkest wardrobe you have.
The Elecraft K2 is quite a small transceiver, made for portable use. Therefore it has fewer indicators of status than many other transceivers. There isn't really much space for this on the rather small frontpanel. But I felt for a long time felt that it should be possible to put additional LED indicators on the K2 but I wanted to avoid drilling holes in the front panel. Here is a method based on using small LEDs in the keycaps, see info from W3FPR/KR5L, as you can always get replacement key caps from Elecraft.
On W3FPR’s recommendation I have used 2 mm LEDs of types HLMP6300 (red), HLMP6400 (orange/yellow), and HLMP6500 (green). They can be bought from Digikey as well as from ELFA in Northern Europe. The first two of the five LEDs that I have added can be connected from the front panel board without additional wiring to other boards.
This YouTube video shows the three first LEDs, the Zero-Beat Indicator, the Split Indicator, and the Audio Filter On indicator:
