PSU tinkering, Part 1

As previously blogged, I've got a couple of 12v 88.7A PSUs that I'm trying to control under arduino. Stage 1 complete - It powers up with a trivial bit of code

/* Arduino control for (ex) server PSU 
 * Andrew Elwell <andrew.elwell@gmail.com> August 2016
 * Released under BSD licence
 */

 /* Controls / Pins based on data sheet available at 
  *  https://belfuse.com/resources/PowerSolutions/SFP1050/bcd20031_ab_sfp1050-12bg.pdf
  *  
  *  A6/B4/C4/D4         +3.3 standby (power to arduino)
  *  A3/B1/B3/C1/C3/D3   Return 
  *  B5(SDA) / C5(SCL)   I2C
  *  B6                  Bring low for PS ON
  *  C6                  AC OK (if high)
  *  D6                  PWR OK (if high)
  *  
  */


#include <wire.h>

int ACOK  = 2;
int PSON  = 3;
int PWROK = 4;
int LED   = 13;

void setup() {
  Wire.begin();                // join i2c bus (address optional for master)
  pinMode(ACOK, INPUT);
  pinMode(PSON, OUTPUT);
  pinMode(PWROK, INPUT);
  pinMode(LED,  INPUT);
  
  digitalWrite(PSON,HIGH) ;   // Stay off until ready
}

void loop() {
  if (digitalRead(ACOK) == HIGH) {
    digitalWrite(PSON,LOW) ;
  } 
  if (digitalRead(PWROK) == HIGH) {
    digitalWrite(LED,HIGH) ;
  } 
}

The one gotcha that I needed to get it working was to also bring PS A0 low (I2C address) and suddenly green led and 12v out!

I've got the power

(It's getting, it's getting, it's getting kinda hectic)

So, another "I should really get round to that" project that's worked its way to the top of the desk is repurposing a skip-dived server PSU (or 4) to be more usable.

Exhibit A - One ex-sun 'SPASUNM-03G' PSU, which spits out a fairly chunky 12v at 86.7A

Since these were pulled from a bunch of servers, the output is a less than friendly set of three paired contacts for +12 and another set of three pairs or the ground. It won't start spitting out 12v when you plug a mains lead in as it needs the PS_ON connector bringing low. Power-one seem to gave been bought out by bel, and the datasheet is available here.

Rather than the (sometimes) crude way people have modified these and similar server PSUs over at RC Groups, I thought I'd hook up an arduino and be "smart"

So - Grand Plan (TM)

* Nice big illuminated push button for on/standby

* LCD display to show status (output / alarms / temp)

* No screaming 'fan-at-maximum' setting all the time

This shouldn't be that hard, right? Arduinos can do i2c and I have a bunch of 3.3v ones to hand, so I can drive this off the stby 3.3v (even that's at 3A on this thing)

TO THE SOLDERING IRON! ... to be continued