"Pat" schreef in bericht
...
Similar to Arfa not being able to see parts on the floor...
Yesterday, I decided to connect a simple circuit to tell me if I left
the garage door open when going to bed. I found a reed switch and
matching magnet in my junk box as well as an LED (with built in
current limiting resistor) and a left over wall-wart power supply.
After connecting it all up I realized the LED was on when the door was
closed rather than open which I preferred. I didn't have a N.O.
switch but I did find an old piece of breadboard and a 2n3904
transistor. All I needed was a 10K resistor to use as a pull up to
make my own inverter. I also wanted to add a 470 ohm R in series with
the LED to lower the current a little. Bottom line: It all works
well, but took way longer than expected. Why? It took a long time to
find the right R's in my old box containing hundreds of 1/4 w R's. The
1/4 Watt resistors in my box clearly have shrunk over the last 30
years! And, the color stripes have all faded to the same shade of
darkness, too. I kept pulling 4700 ohm R's from the box when looking
for the 470 because the red stripe looked brown to me. I'm glad I
don't do this for a living anymore!
Pat


Well, growing old may not be funny. Being old even less. But it seems to be
the only way to live longer and most of us want to.

As for the colors on resistors, they are often unreliable even on new ones.
Even with perfect eyes that can see all colors sharp and clear you often can
only guess what color it is supposed to be. So I always keep my Ohm-meter
nearby.

petrus bitbyter