LED status recognition and activation of another circuit - Page 1
Forum section: electronics / beginners

author: TerraByter
author_rank: Contributor
timestamp: January 14, 2021, 09:26:35 am
content: I need to do something and i need your help.I have a device, device have a Led, the led are ON. With a procedure from the device the Led start Blinking, or as the manufacture of the device say "Blinking once every second".Can I somehow control the LED to figure out when it enters this state and activate another circuit?

author: drdm
author_rank: Contributor
timestamp: January 14, 2021, 12:03:34 pm
content: Depends on your specific situation, but probably yes.You can hook up a differential amplifier in the LED pins and measure when there is a voltage on the LED, or if you don't need to look at the LED and it is powerful enough you can enclose it together with a photo-diode or a LDR and get the signal from there.

author: TerraByter
author_rank: Contributor
timestamp: January 14, 2021, 12:12:57 pm
content: Quote from: drdm on January 14, 2021, 12:03:34 pmi believe that are the best choice, can you please give me more details?

author: ledtester
author_rank: Super Contributor
timestamp: January 14, 2021, 12:31:00 pm
content: Another option would be to replace the LED with an optocoupler.Quote from: TerraByter on January 14, 2021, 12:12:57 pmFor circuits which can determine whether the LED is on or off, search for "detector LED LDR" or "light detector LDR", e.g.:https://www.electronicshub.org/light-detector-using-ldr/https://circuitdigest.com/electronic-circuits/light-detector-ldr-circuit/You'll probably need to tell us more about the circuit you want to control for better answers. Note that trying to detect when an LED is flashing (as opposed to just on or off) might present some difficulties.

author: TerraByter
author_rank: Contributor
timestamp: January 14, 2021, 12:33:57 pm
content: Quote from: ledtester on January 14, 2021, 12:31:00 pmI want when the led start blinking to activate a 555 timer.

author: ledtester
author_rank: Super Contributor
timestamp: January 14, 2021, 02:45:59 pm
content: I'll suggest the following two approaches.1. Use a phototransistor to detect whether the LED is on or off. You can monitor the output of the phototransistor with an Arduino. Then you can do whatever timing you want in the Arduino or have it send a pulse to another circuit or whatever.2. Use a phototransistor to detect whether the LED is on or off. Connect it to a "time-delay relay module". These modules have trigger inputs so the timing can begin via an external signal. The relay then can turn on whatever circuit you want after your programmed delay.Here is one example of these kinds of modules:http://www.icstation.com/time-delay-relay-module-digital-display-control-timer-switch-trigger-cycle-module-smart-control-p-13348.htmlA basic introduction and demo of a phototransistor:http://www.learningaboutelectronics.com/Articles/Phototransistor-circuit.php

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 17, 2021, 06:35:06 pm
content: Quote from: TerraByter on January 14, 2021, 12:12:57 pmWhy is there a differential amplifier? From a cannon on sparrows? It is enough to turn on the LED circuit in series with the any optocoupler with its current-limiting resistor Or remove the current-limiting resistor, and insert an optocoupler with a resistor instead. If it is possible to combine Gnd devices, then just take the logical signal directly.