Looking for assistance on a "CLUB" project

I have just been starting to get into the Arduino family of projects, there is a lot to learn here and I am certain that I have bitten off more than I can chew. I took electronics in the early 2000's, and have been a field service technician in low voltage electronics for the past 13 years. Here is my difficulty.

A local RC car racer contacted me about RC drag racing and having a large race at the Syracuse Nationals this year. We have a couple of Traxxas DTS-1 drag racing systems that kind of do what we like, but the starting tree is incredibly small and difficult to see in the daylight. I bought a bunch of 5volt relays and 60mm push buttons with 12vdc light bulbs. My mental theory at first was to simply use the input voltage of an LED on the tree to trigger a relay and light my bulbs. Simple follower circuit. Well, that did not work at first, until I found that the LEDs were a constant +VDC with negative trigger. I moved the jumpers on the triggers and 10 of my 16 bulbs now follow the LEDs. The other 6 bulbs do not work as there are multiple LEDs on the tree that are triggered at the same time and I have not found a connection point to simply "hack".

What I want to attempt is to trigger a NANO output based off of a voltage reference of an LED used as an input. I do not know if this is possible, but anybody willing to help with a sketch, would be greatly appreciated.

Thank you in advance,
Rob Warren

MODERATOR EDIT : email address removed. Suggest replying here or via a PM if interested in helping

How about using analogRead() instead of digitalRead() on a suitable input pin ? That way you could tune the voltage that the input reacted to rather than relying on it going explicitly HIGH or LOW ?

Hello Rob, welcome.

I do not understand your description of what you are doing, maybe someone else will but if one person doesn't then there will be others who don't. You say you trained in and work in electronics so producing a schematic of what you propose should be easy for you, it would certainly make it easier for anyone trying to help to understand what you are trying to do

At the end of your question you ask for code, if you want someone to write code for you the correct place for your question is Jobs and Paid Consultancy, expect to pay.

Otherwise I suggest Project Guidance might be a better place for your question.

Yes, that is what I was reading about. Now I just need to find more information, and understand it HAHAHA. When you google anything on LED it is simply how to turn it on with an Arduino and that is pretty basic, but to turn on an output based on the status of a different circuit, that is where I am finding difficulty. Thank you. I will be researching with a much better description with proper terminology!

So, are you asking to have an arduino read the status of an LED that is in a separate system?

I assume that you just want to echo what the little light tree does with bigger bulbs that are easier to see.

While you could do that with an Arduino, I'm not sure what it would give you over discrete electronic components.

If you need 16 inputs and sixteen corresponding outputs though, you'll need an Arduino with more pins, or port expanders.

Correct. It is either I read these other LEDs or simply remove them and use Infrared Emitter and detector to trigger my isolated relays... not using Arduino at all. But, if I can use the existing start tree, with Arduino, I would prefer that...

Perfectly stated. I can measure 10 of the 16 LEDs currently and trigger my relays, however there are 6 LED matrixes, (Multiple LEDs) that I can not simply locate a high or low point in the circuits to trigger my relay inputs.

Pick either leg of one of the LED strings near the middle of the string and measure the voltage between there and GND on the Traxxas. Does it change when the string of LEDs turns on or off ?

Yes, I get 2.5 VDC on one side of an active LED. Unfortunately not enough to trigger my 5 volt relay on its own...

Detect the 2.5V using analogRead() and output 5V on a digital pin, or if you have gone off the idea of using an Arduino just use a MOSFET

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Thank you for your input. It really got me thinking about what I really needed to do, and how to simplify my project. I thought about your suggestion most of the night and had to think back to my electronics classes some 20 years ago, and there was the answer. LM339n quad comparitors is the perfect solution! My LEDs on the tree are working perfectly, and the 5VDC relays and 12VDC lights are following properly. Thank you again for presenting a proper rabbit hole to focus my attention on! Works like a charm!

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Hello sorry to chime in but I have been wanting to do this exact thing for some time.I haven't been able to find any info on the subject. I am decent with soldering and small projects but have no clue where to start.I hate to ask this but is there anyway you could maybe dumb it down for me or possibly post a video of how to do it? I am disabled and in my later years so the little tree is extremely hard for me to see especially in the daylight. If you could help me out I would greatly appreciate it.And if not I understand completely 100%.Thank you very much for your time.

Hello
post your current sketch well formated and in code tags to see how we can help and a picture of your hardware.