Arduino Master/Slave detection method for driving LEDs

Hey Forum.

I am working with Neopixels and creating a sort of light box with them. I am looking to have them stackable and rather than have the user need to plug in 3-4 (plus) different power supplies, I would like to have the feature of having a jumper cable go between them that will pass on power/data/gnd, and input it into the slave board and have it bypass the arduino on the new box. Each unit is identical.

Please see the attached PDF for a schematic diagram showing the conditions. PLEASE NOTE ON THE ATTACHED PDF THE MASTER BOARD IS AT THE BOTTOM AND IT GOES UP THE DIAGRAM, NOT DOWN. BIT CONFUSING, SORRY.

I would consider myself an amateur hobbyist and there is probably many ways to tackle this but would like to know if any pro's have a good approach. Here is a picture of my concept at a solution that uses 2 power ports, but ideally it would be able to know that there is a master arudino driving the array already so that any power injection doesn't attempt to turn on any additional slave arduinos.

(please see the ATTACHMENT schematic pdf of the overall goal first before looking at this picture, as this picture wont make any sense about what I am trying to do. )

And here is a design document that i've drafted up to help you understand the reason for this.

Slave Detection Method
Design Document.

Goal:
To design a method to detect when a connection (both power and signal) has been made to an identical device. Each unit to know which device is receiving the power source. In order for the microcontroller to “pass through” the slave device.

Use case:
The user purchases an additional unit to extend the use of the main product. The user has limited power points available and it is convenient to have less wires.

Advantages:
The user can purchase multiple devices and have only 1 power adaptor to deal with. Making full use of the rated amperage of the power supply.

Design:
A method to detect when a connection has been made to an identical devices through the use of a “jumper cable” to bridge the connection. The jumper cable is unspecific at time of document. However it will need to be rated for approx 6amps, and ideally will need to carry a 800Hz data line too.

Fail Safes:
The master arduino driver board will have detection code to determine how much amps the circuit (theoretically through counting the amount of slaves) is drawing, and will have soft limits to stop additional power from being drawn, possibly by reducing the brightness of the led’s.

Voltage Drop:
Voltage drop will occur when multiple units are connected and will discolour the leds. In order to prevent the brightness drop, a secondary power source can be injected into the circuit via the power port of the unit at the end of the chain.

Schematic_LightBox_Arduino_20190907173027.pdf (59.4 KB)

I've deleted your other cross post @DanielDoesDesign.

Cross posting is against the rules of the forum. The reason is that duplicate posts can waste the time of the people trying to help. Someone might spend 15 minutes writing a detailed answer on this thread, without knowing that someone else already did the same in the other thread.

Repeated cross posting will result in a suspension from the forum.

In the future, please take some time to pick the forum section that best suits the topic of your question and then only post once to that forum section. This is basic forum etiquette, as explained in the sticky "How to use this forum - please read." post you will find at the top of every forum section. It contains a lot of other useful information. Please read it.

Thanks in advance for your cooperation.

Hi,

If D8 is setup as an output, then Nano 2 will be a problem, as it is connected to the output of the master Nano LED strip.

Tom.. :slight_smile:

Can a non powered nano or any device for that matter effect the continuation of a data line if it is not powered? I am investigating Logic Gates to prevent power to the 2nd nano. The best implementation I have is that use a few transistors and resistors to create a Logic invertor. The problem then becomes that it stops the 2nd arduino from running, but if you plug in a 3rd, then it switches back to trying to run the 3rd.

Hi,
Why do you need the Nanos in the other units if the master is controlling the strip?

Don't forget that as you add more and more to the end of the strips, the current required will be higher and higher and the narrow traces on the strips will cause a voltage drop.

Thanks.. Tom.. :slight_smile: