One problem would be that I have an access control system that has 10 doors in it. Each door has a NodeMCU, a card reader, a programmable LED and a step down converter to 12V-5V and a relay. There is a power supply that emits 12V, 6A and 70W. Power is supplied to the doors via a UTP cable. The problem is that 5 out of 10 doors boot into responds properly to the activities I program, and the other 5 get power that turns on but doesn't boot properly. Before they were installed all were tested and all worked.
Using how many strands ? UTP is not very thick. It is not meant as a power cable but as a data cable.
Just the get it clear, a single unit is powered and has it's own card reader, and the wiring and the program are the same for each unit ? and some work and some don't. It makes sense to look at the way they are powered.
I use the blue+blue/white+orange+orange/white for +12V and green+green/white+brown/white+brown for -12V. Yes, Every single unit has her own card reader, with same code. I group 4 units to a power supply.
Deva_Rishi is right on. I would venture to say the ones that are not working are on longer cable. If you want a better answer we also need to know the load, distance and tolerable voltage drop. If the door opener draws a surge we need to know that as well. How is the wire routed and the length of each segment. A drawing showing this would be a big help. Also links to the converter and power supplies.
Uh. Thanks a lot. That was on my head too. But what about the pins. I read something about GPIO0, GPIO15 and GPIO2, this 3 pins can block the normally boot up. That can be a another problem ?
The intresting thing is. Every single unit has her own dc dc step down converter. So from power supply is comming 12V or 10V doesnt matter and its converted from 5V to maximum 5.30V.
Yes, you need a pull down resistor on GPIO15, maybe 3k3 to ground will work. I've not had to put anything on the other pins you mention to make an ESP8266 work but if you still have problems after pulling down GPIO15 then investigate the others.
For the power try a 1000μF (or anything similarly large) capacitor across the supply close to the ESP8266.
Something isn't right but I don't know what. I agree that D8 is GPIO15 but I don't agree that it is SDA. I have some D1 minis:
and:
Both most definitely have SDA on GPIO4, not GPIO15. I guess you need to get to the bottom of this discrepancy, I don't know the answer, hopefully someone else does.
I don't know, maybe. When I first used an ESP8266 board I came close to giving up as they were very unreliable, sometimes starting, sometimes not. Then I discovered the need to pull GPIO15 down, after that they worked perfectly well. You could just try the pull down resistor anyway as an experiment, it won't do any harm, it just might not do any good.
Yes they can, but that would not explain why the other units do work.
I think Perry has explained about GPIO 15.
GPIO 0, GPIO 1(TX) & GPIO 2 should not be pulled 'LOW' at boot, that means anything you connect to those pins as an output, should be connected 'Active LOW'
Just to verify, how about you post a full schematic of a single unit.
