Hello,
I am doing microbiology experiments with bacteria in school and I need a quick and easy way of determining roughly, how many bacteria are in a test tube. The easy option is to use a spectrophotometer, basically shine a light through the test tube and a sensor on the other side will get a light level reading and determine the "murkiness" of the liquid and from that you can determine the number of bacteria. I don't have a $1,000 spectrophotometer, but it seems like it shouldn't be too hard to make.
I am thinking an LED or Laser diode from a laser pointer at one side of the test tube and a photoresistor at the other side. The voltage at the photoresistor can determine the number of bacteria. The question is how sensitive can this "makeshift" sensor be. To .01V (multimeter)??? Also this would be powered by a battery which would slowly loose power and change my readings from test to test....Would a wall wart as the supply solve this problem?
Suggestions, ideas, and guidance would be really appreciated.
Thanks,
George L.