Flashing light when door opens

[Bm5360]

Hi, I have a flashing LED, and when someone opens the door the LED flashes and when they shut the door the LED stops flashing.
This what I am trying to do... When someone opens the door the LED flashes and continues to flash even after they shut the door, and I would need to push a button to reset (stop LED from flashing ) and be ready to flash again the next time someone opens the door.
Thanks !

 

[73's de Edd]

Sir Bm5360 . . . . .

A bit mo' info needed.

Just initially guessing . . . . . . but . . . . . is this a front store/display room, where a customer might enter and trip the temporariy flashing LED.
Now is that flashing LED ( but with it using no additional AURAL alarm ? ) in an adjunct room where you can be a diddling and a piddling on other tasks . . . . . . 98 23/67ths % of the time?
You then go to the other room to greet the person CONSIDERING that you would even see that FLASHING LED.
( ME . . . I would be needing a pulsed strobe ! and a KLAXXON horn in full dive alert status )
Soooooooooo . . . .now are you OK with the simplicity of just pressing a button in the display room to abort that now MODIFIED . . . .constantly flashing LED, or will you be needing a plushy upgrade to a gold plated and ermine lined pushbutton RF fob.
Also is the current system running hard wiring to the back room LED and using AC power . (wallwart) or is it using battery power ?

73's de Edd

 

[AnalogKid]

Does the LED flash by itself, or is it driven by a flasher circuit?
What power is available to run a latching circuit?
How much power does the LED need?

ak

 

[Bluejets]

Basic start/stop with hold-in on start button.

 

[AnalogKid]

This can be done with a small electronic circuit or with a relay. Which are you most comfortable with wiring?

ak

 

[Bm5360]

Does the LED flash by itself, or is it driven by a flasher circuit?
What power is available to run a latching circuit?
How much power does the LED need?

ak

I am currently just using a simple transistor for blinking an led. I really won't use this, this was just for experimenting. I will use what ever circuit (components) needed.
This won't be used for any security or anything like that. It is something I thought of and would like to do. It is just to let me know if someone has been in a room.
Would you know of a website that would have a schematic of something like this?
Thanks

 

[AnalogKid]

What power (voltage, current) is available to run a latching circuit?
How much power does the LED need?

ak

 

[AnalogKid]

Pretty easy to do this with a CD4093 quad NAND gate. One gate as the oscillator, two as the latch, an external 2N7000 small MOSFET to drive the LED, and one gate as an inverter to drive the transistor. One 14-pin chip, 1 transistor, 2 caps, 3 resistors (plus whatever is current-limiting the LED). Extremely low standby current.

The same functions can be done with one ULN2003 or 2004 transistor array. Two transistors as a latch, two as the flasher, two for internal control, and one spare. It is the same circuit blocks as with NAND gates, but with all discrete transistors you can see how the circuit really works. One 16-pin chip, 2 caps, 4 resistors (plus whatever is current-limiting the LED).

Any of the transistors can drive the LED directly, and the part can run on anything up to 50 V. Beefy little puppy. Low standby current, but not like the 4093.

Note - if you want to be able to reset the circuit while the door still is open, that changes things a little.

ak

 

[Bm5360]

Pretty easy to do this with a CD4093 quad NAND gate. One gate as the oscillator, two as the latch, an external 2N7000 small MOSFET to drive the LED, and one gate as an inverter to drive the transistor. One 14-pin chip, 1 transistor, 2 caps, 3 resistors (plus whatever is current-limiting the LED). Extremely low standby current.

The same functions can be done with one ULN2003 or 2004 transistor array. Two transistors as a latch, two as the flasher, two for internal control, and one spare. It is the same circuit blocks as with NAND gates, but with all discrete transistors you can see how the circuit really works. One 16-pin chip, 2 caps, 4 resistors (plus whatever is current-limiting the LED).

Any of the transistors can drive the LED directly, and the part can run on anything up to 50 V. Beefy little puppy. Low standby current, but not like the 4093.

Note - if you want to be able to reset the circuit while the door still is open, that changes things a little.

ak

Thanks. I think I will try the CD4093.

 

[AnalogKid]

Here is a first pass at a CD4093 version. Adjust R1 and C1 for the flash rate. C3 is a power-on reset.

ak