I am in need of code and schematic for a single 5mm Green LED in OFF state that is waiting for a red LED to turn ON
When red LED turns ON, green LED does nothing (stays OFF)
When the red LED switches OFF the green LED turns ON
and stays ON until power is interrupted
The trigger mechanism must be an optical sensor that senses the red LED is ON
not wired to the red LED circuit.
Power can be any DC voltage.
I also have access to components,
$150.00 USD budget
Can the red LED be optically shielded from stray light in it's environment? Where is it? On a panel or something? Can something be installed/secured on top of it? Edit - also must it remain visible?
You'll get more takers if you post more details.
I also have access to components,
Does this mean you will build it yourself, or that the components will be supplied to the builder?
red LED is mounted under dishwasher shining down about 3 inches from floor, so some natural light will be present. If a photo diode or photo resistor is used, it can be mounted about 1 inch from red LED.
Yes* I will build my-self & acquire components
Basically I want a green LED to shine on floor to let me know dishes are clean.
Thanks for taking notice
Powered from??? Is the power tied to the Dishwasher power somehow, or do you manually switch it on/off?
Power from a DC power supply, manually switched. Nothing attaches or wired to dishwasher.
power is interrupted (via external switch when door is opened.
But can have constant power as well. I was thinking when power is interrupted to arduino (if that is what would be used) the code would re-set
Do you really want to code that or would you be fine with a opamp + 2 resistors?
Not sure opamp is the solution. That sounds like a nightlight. I think (and could be wrong) code is needed to trigger the green LED to wait untill the red LED turns OFF
Othewise the geen LED would just turn on anytime the red LED is OFF
If you power this with, e.g., a toggle switch, then the circuit simply needs to power up in the off state, and wait for the red light to go off. (would be a negative, or positive, edge trigger depending on circuit topology). Lots and lots of ways to do that, using off the shelf modules, wire-yourself analog circuit, or yes, an Arduino. The latter would be fine as a newby project, though I'd call it gross overkill at best otherwise.
As an example, there are modules like this on Amazon:
While I didn't check to see if this would do what you want, it's just a matter of selecting the right one, and adding a photosensor for the LED input. But, if you need someone to do that for you, someone else will have to jump in, with their own solution and pet critters. Personally, I'm out of project time.
With the appropriate circuitry some red leds can be used as sensors. LEDs detect a much narrower band of light having peak sensitivity at a wavelength slightly lower than the wavelength these emit. For example, a transparent red LED emits around 660nm light and responds better to orange light at 610nm. This acts like a filter. Also depending on the LED and its radiation pattern it can be narrow eliminating a lot of spurious light.
As @gilshultz says, you can use an LED as a sensor, or a silicon photodiode or phototransistor.
However
Unless you can find a way to exclude natural light the system wont be reliable. You CAN detect MODULATED light in the presence of competing illumination. (by detecting AC, or better with a lock in amplifier)
You can also use a filter to exclude some frequencies of light, but natural light and light from a red LED share part of the same spectrum.
This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.
