I wanted to use one of the cheap USB power meters as a general DC
voltmeter and ammeter.
The label on the module gives a range of 3.5 to 7 V and 0 to 3 A.
Inside is a Holtek HT46R064B 8 bit microcontroller with an analog to
digital converter.
The modification is very simple. Cut a USB extension cable in half
and use the power wires as the input and output connections. In a normal
USB cable, red is positive, black is ground, and green and white are the
data wires.
I tested it with a single cell LiPo battery and it worked.
A monochrome camera can have better sensitivity and useful spatial
resolution because every pixel responds to the available light instead
of being divided into red, green and blue pixels by a Bayer color
filter.
For example, a typical Bayer pattern has approximately 25 percent red
pixels, 25 percent blue pixels and 50 percent green pixels. When
photographing something that is mainly green, most of the useful signal
comes from only half of the sensor pixels.
I wanted to try removing the Bayer filter because Raspberry Pi did
not offer a monochrome camera module at the time. I had upgraded my
cameras to the newer version, so I used the old modules for the
experiment.
The Pi NoIR camera is not monochrome. It only lacks the infrared
blocking filter. It still has the Bayer color filter on the sensor.
Removing the filter was neither quick nor easy. The lens holder is
attached with a thin layer of epoxy. The safest method I found was to
release one corner carefully and use that opening to separate the board
from the holder.
Four cameras died during the first attempts. Two were damaged while
opening the lens holder and two during the actual filter removal.
There are extremely fine bond wires around the edge of the sensor.
Touching or shorting them will kill the camera. I did the early attempts
without a microscope because I was too lazy to drive to TAMI. The later
close up photos were taken through a Mantis microscope that I bought
afterward.
The fifth camera was scraped while it was operating so I could see
exactly when something went wrong, and that attempt worked. Very little
pressure is needed. Too much force can move the sensor die and tear the
bond wires.
There also appeared to be another coating below the Bayer layer,
possibly an antireflection coating, although I was not certain.
I later killed that camera while adjusting the focus. The hot glue
holding the lens socket came loose, moved the sensor and tore more bond
wires, bringing the casualty count to five.
I tried several solvents in an ultrasonic cleaner without success.
Later, photoresist remover followed by cleaning solvent removed the
filter without damaging the sensor, which was a much better method than
scraping it with a knife.
The first finished image had the focus slightly off, but the
monochrome conversion worked.
