P
Pat
Guest
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
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