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Reed switch circuit puzzle.

Thread starter #1
Hi, I want to make a circuit with a reed switch and a couple LEDs. I want the LEDs to alternate when the reed switch is activated. I want to have a normal on off switch in the circuit so I can turn the entire circuit off completely when it's not in use.

example:
One LED is Blue and one LED is Green.
When I turn the circuit on with the normal on off switch the blue LED turns on.
And then when I pass a magnet by the reed switch the blue LED turns off, and the green LED turns on.

I would also be interested in the option of either:
having the circuit automaticaly reset back to blue on/green off after a 20 second delay
or
having the circuit reset with a second pass of the magnet.

Can anyone draw me a circuit for this?
 

AnalogKid

Well-Known Member
#2
Your two options are two different circuits. Either one can be done with a 555 timer IC. Are you familiar with this part? The automatic reset after 20 seconds would be the monostable circuit. The circuit that toggles back and forth between the two colors with each switch event is a toggle flipflop circuit. It is not one of the applications on the datasheet, but it is a well known circuit.

ak
 

gophert

Well-Known Member
Most Helpful Member
#3
Hi, I want to make a circuit with a reed switch and a couple LEDs. I want the LEDs to alternate when the reed switch is activated. I want to have a normal on off switch in the circuit so I can turn the entire circuit off completely when it's not in use.

example:
One LED is Blue and one LED is Green.
When I turn the circuit on with the normal on off switch the blue LED turns on.
And then when I pass a magnet by the reed switch the blue LED turns off, and the green LED turns on.

I would also be interested in the option of either:
having the circuit automaticaly reset back to blue on/green off after a 20 second delay
or
having the circuit reset with a second pass of the magnet.

Can anyone draw me a circuit for this?

These three will get you started. The left two circuit uses the fact that green LEDs generally have a 2 volt drop and blue have 3 volt drop.

The middle one needs a MOSFET Transistor and there will be a short transition time (fade from green to blue after 20 seconds). Fast from blue to green.


52ECF451-BDFA-4B46-B341-CB577CB23F3C.jpeg
 

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