Triggering Relay from LED source. (-6V when OFF and +1.6V to +2.5V when ON)

I am doing a project that are not triggered by Arduino but utilizing a relay with a signal from LED signal.

I managed to trigger the relay only with 1 single relay type. OPTO single. OPTO 8 channel will unable to be triggered. Tried SSR also relay unable to be triggered.

Upon further investigation. I have notice the below are the value of LED signal voltage.

LED OFF Voltage : -6V
LED ON Voltage : +1.6V to +2.5V

Differennt in voltage during triggering 2.6V - 3.1V

I do believe the problem lies at the -6V when the led in in OFF possition.

Basically… i wish to use the same input powering the small LED to a brighter and larger LED powered by 12VDC/24VDC/240AC.

So you have a 3V regulator, that normally produces a +3V output. Does your relay even activate at that low voltage? Usually they need 5V.

Also you claim you have a -6V level - where does that come from? Based on your schematic this is impossible.

LED on voltage 1.6-2.4V that sounds like a typical voltage drop. Where is your current limiting resistor or other current limiting device? Why and how is that connected to the relay, instead of to the power source?

The LED came from a different device. I have measure the output at the LED. It has multiple LEDs but below is the measurement

LED 1 When OFF -6V When ON +1.8V
LED 2 When OFF -6V When ON +1.8V
LED 3 When OFF -6V When ON +1.8V
LED 4 When OFF -6V When ON +1.8V
LED 5 When OFF -6V When ON +2.5V
LED 6 When OFF -6V When ON +2.5V

(LED from my equipment. The idea is to make the LED brighter on secondary display board)

yes, the Relay triggered with assistant of 3V power source (As indicated in my attached sketch).

Adjusted on the other Relay at 5V it still does not turned on (For the other relay).

On my post i have attached the sketch.

Your response are most appreciated.

Clearer sketch of the current situation.

|479x500

I am pretty sure the -6V is the major culprit. Not sure what to do to overcome this issues.

Not sure what you're trying to do with that cobweb.

Normally, when you want to detect/use the state of a LED on another device, you use an opto coupler. Opto LED if possible in series with the existing LED. Parallel is also possible with a ~220ohm resistor in series with the opto LED.

Opto transistor between Arduino pin and Arduino ground, with internal pull up enabled. Leo..

Thank you for your response. The circuit are not connected to Arduino. I am using my Arduino for other purposes.

For this particular task, i just wish to minimize the design work and cost for this particular LED display since the only problem with it is only it is weak. I wish to add a 12V buzzer and 12V led on it. Relay with low trigger should work but the problem is just the -6ve polarity when the LED is in an off state should it were 0V when in an off state, i do believe it will not be an issue.

But i shall try to look for an opto isolator to see will it works or otherwise. But may you advice on any specification of the opto-isolator that you think might work in my case?

Wawa: Not sure what you're trying to do with that cobweb.

Normally, when you want to detect/use the state of a LED on another device, you use an opto coupler. Opto LED if possible in series with the existing LED. Parallel is also possible with a ~220ohm resistor in series with the opto LED.

Opto transistor between Arduino pin and Arduino ground, with internal pull up enabled. Leo..

If you have -6V across a LED when it is off you are very close to damaging it. Your schematics are useless because their is no labelling on the wires going into the blocks so we can't tell what the wiring is supposed to be.

If their is not an Arduino involved why are you posting on an Arduino site?

Grumpy_Mike,

I am using the Arduino with a relay for another section of the project delay off for mp3 audio output and other auxilary. It works well. To complete the project, i just wish to use a third party LED indicator using the same relay that i used for Arduino without using a second arduino board.

I learned something here from somebody that willing to assist and i have use an opto isolator to provide protection to the secondary board part board.

Worst case scenario i will have to use secondary arduino for this purpose.

We are all willing to assist some one who is willing to cooperate. Why do you insist in not cooperating with us?

I am trying to. That explained the sketch but you said it is useless.

I have mentioned that in this particular circuit, it is not connected to Arduino since i wish not to have 2 arduino in the design due to it is in a different compartment.

But it looks like that is no where around it unless i am utilizing Optocoupler to sent signal to Arduino and have Arduino triggering the relay with a straight forward command.

Grumpy_Mike: We are all willing to assist some one who is willing to cooperate. Why do you insist in not cooperating with us?

That explained the sketch but you said it is useless.

So make it not useless. Label what the wires are going into those blocks.

Are they coil connections? Are they switch contacts? If so which are normally open, normally closed and common. Show the two points you use to measure these voltages.

Draw how you connect the wires from the LED to the Arduino.

Post a photograph, give us something to work on. We can not see what you can see, we can only work on the information you have given us. And what you have given us so far is precious little or impossible.