APC UPS Shutdown Manager

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I work in an office where working late in the night is the norm including weekends.. This post is not about my office or about the work we do late into the night but about a problem statement posed to me by my subordinates. It goes like this..

The office or rather the building rules demand that we shut down (hard off) all electrical equipment once the office is finally shut for the day. This means that our office servers also requires to be shut down along with the UPS (APC SMART 2200). Now this has nothing to do with our office trying to be green but more to do about obviating any fire risks.

So, whats the problem. The problem is that, once we (management) leave the office, the duty staff has to shut down all the equipment including the servers. The issue is that our two servers running WindoZe 2008 R2 and WindoZe 2003 take about 15 minutes to shut down cleanly. And the UPS then needs to be shutdown afterwards. 15 minutes may seem a small time interval for an office which works routinely for 15+ hours in a day in a single shifts 7 days a week. But at night 2330 when its time to go home every minute looks like an hour to the subordinate staff.  So the problem was narrated to me over a short tea break. Since I believe in working Smarter and not Harder, I decided to save 15 man minutes every day.

Thus (coming to the point), this post describes a circuit / contraption I have devised which shuts down the  UPS once it detects that both the computers dependent upon it have secured for the day.

Detection of the state of the servers is done by pinging the servers at a predetermined time interval.  However generally since persistent ICMP pings are blocked by firewalls, I have decided to do an ARP request to find the state of servers. So in a nutshell if a server responds to ARP request it is deemed to be alive.

The Arduino board communicates with the UPS over a serial port. The serial communication is done at 2400 8N1, No handshake. The communication protocol used is well discussed and elaborated here. Once the micro-controller detects that the servers are down for a defined time interval, it is assumed that the servers are off and a shutdown command is then  issued to the UPS via Serial Port.

However, during the day time there is a possibility that the network (read physical media) might itself be under maintenance or the network switch might be down due to a power outage, so there emerges a possibility that the server may not respond to any ARP requests, leading to a shutdown of the UPS and thereby causing an unclean server shutdown.

To circumnavigate this issue, it becomes  essential that the microcontroller  knows the time of the day and shutdowns the servers only after 2000 hrs . The solution to this problem is a simple RTC clock. Now how does the RTC update its own time.. NTP. One of my server functions as an NTP server and I decided to use the same to update my RTC clock one when its booted up.  Once this was done, the code was modfied accordingly.

RTC Module

Knowing time of the day was also essential since I had to switch on the UPS and then the servers. UPS is switched on via a serial command and the servers are switched on via a Wake on Lan (WOL) magic packet. Not implemented since I have configured the Server’s Bios to WakeUp on restoration of power on.

I have also thrown in a DS18B20 temperature sensor to measure the ambient room temperature.

The system state including UPS statistics are available on a webpage… The Arduino  board also behaves like a webserver.

Connection Matrix




Code (Sans NTP +RTC Part)

#include <OneWire.h>
#include "EtherShield.h"
#include <Wire.h>
#include <RTClib.h>

//---------------defines for EtherShield----------------------
#define MYWWWPORT 80               //www server port
#define BUFFER_SIZE 1200
static uint8_t buf[BUFFER_SIZE+1]; //data buffer
static uint8_t mymac[6] = {0x54,0x55,0x58,0x12,0x34,0x56 };
static uint8_t myip[4] = {159,12,23,148};
static uint8_t Server1ip[4] = {159,12,23,160};
static uint8_t Server2ip[4] = {159,12,23,150};
static uint8_t ntpServer[4] = {159,12,23,150};
long server_poll_interval=30000; //query/ping server status every n seconds
uint16_t print_webpage(uint8_t *buf); //function prototype
EtherShield es=EtherShield(); //instantiate class

//---------------defines for UPS Manager----------------------
long serialtimeout=500; //time in milliseconds to timeout serial port response
long serial_poll_interval=60000; //query ups every minute
int shutdown_grace=5; //time in minutes after which shutdown command will be issued to ups
int ups_shut_flag=2;//1-> UPS OFF 0->UPS ON 2-> dont know
long shutdown_interval=0;
int server1=0; //server1 flag
int server2=0; //server2 flag
boolean ups_state=false; //ups flag
char line_voltage[6];
char line_freq[6];
char batt_voltage[6];
char load_voltage[6];
char load_factor[6];
char batt_level[6];
char estimated_runtime[6];
char status_flag[6];
char ups_flag[6];
char response[5];
char internal_temp[6];
char external_temp[6];
char time_string[50];

//---------------defines for RTC , NTP & DS18S20 Temperature Module--------------------
OneWire  ds(6); //Sensor connecd to pin 6
#define SECONDS_FROM_1900_TO_1970 2208988800  
uint16_t http200ok(void)
  return(es.ES_fill_tcp_data_p(buf,0,PSTR("HTTP/1.0 200 OK\r\nContent-Type: text/html\r\nPragma: no-cache\r\n\r\n")));

// prepare the webpage by writing the data to the tcp send buffer
uint16_t print_webpage(uint8_t *buf)
 // get_RTC_time(time_string);
  uint16_t plen;
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<center><p><h1>Welcome to Ishan-s UPS Shutdown Manager V0.1 </h1></p> "));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<table border=1 align=center>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>Server 1 Status</th><th>Server2 Status</th><th>UPS Status</th></tr>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><td align=center><strong>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("</strong></td><td align=center><strong>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("</strong></td><td align=center><strong>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<h2 align=center>UPS Status</h2>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<table align=center border=1>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>Line Voltage (Volts)</th><td>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>Line Frequency (Hz)</th><td>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>Battery Voltage (Volts)</th><td>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>Output Voltage (Volts)</th><td>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>UPS Load (%)</th><td>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>Battery Level (%)</th><td>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>Internal Temp(deg C)</th><td>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>External Ambient Temp(deg C)</th><td>"));
  plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<tr><th>Estimated Runtime (Minutes)</th><td>"));

  if (plen >= BUFFER_SIZE)
    plen=es.ES_fill_tcp_data_p(buf,0,PSTR("HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n"));
    plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<center><p><h1>Welcome to Ishan-s UPS Shutdown Manager V0.1 </h1></p> "));
    plen=es.ES_fill_tcp_data_p(buf,plen,PSTR("<p><h1>Error: buffer is too small...</h1></p> "));


void setup(){
  // Initialise SPI interface
  // initialize enc28j60
  // init the ethernet/ip layer:
  es.ES_init_ip_arp_udp_tcp(mymac,myip, MYWWWPORT);
  //calculate shutdown interval
  //init serial port


void loop(){
	unsigned long starttime,servertime;
	int shutcount=0;
	uint16_t plen, dat_p;
	while(1) {
		while ((millis() - starttime > serial_poll_interval) && (ups_shut_flag!=1)){

			if (response[0]=='S' && response[1]=='M'){
                        //read TIME & temperature

		while (millis() - servertime > server_poll_interval) {

			server1=arp_ping(Server1ip); //ping server1
			server2=arp_ping(Server2ip); //ping server2
                        if (server1==1 || server2==1){
			//do not switchoff if any of the server is alive
			if (server1==0 && server2==0){
			if ((shutcount>shutdown_interval) && ups_shut_flag!=1){
				shutdown_ups();//issue powerdown command to ups
		// read packet, handle ping and wait for a tcp packet:
		dat_p=es.ES_packetloop_icmp_tcp(buf,es.ES_enc28j60PacketReceive(BUFFER_SIZE, buf));
		/* dat_p will be unequal to zero if there is a valid http get */
			// no http request
		// tcp port 80 begin
		if (strncmp("GET ",(char *)&(buf[dat_p]),4)!=0){
			// head, post and other methods:
			dat_p=es.ES_fill_tcp_data_p(buf,dat_p,PSTR("<h1>200 OK</h1>"));
		// just one web page in the "root directory" of the web server
		if (strncmp("/ ",(char *)&(buf[dat_p+4]),2)==0){
	}//end of while loop
}//end of main loop

void sendtcp(uint16_t dat_p){

char *query_ups(char cmd,char *temp){
	int i=0;
	long Stime;
	//flush serial port
	//senda command on serial port
	Serial.print(cmd);//wakeup UPS from dumb mode
	//wait for reply till timeout
          //read serial input
	      char inChar=Serial.read();
	      //add it to the inputString:
	*(temp+i)='\0'; //null terminate the buffer
	return temp;

int arp_ping(uint8_t *remIP){
	int state=0;
	uint32_t endtime,dat_p;
	uint16_t timeout=5000;//time out ping after 500 milliseconds
	//send an arp request to get the mac address of the remote IP
			return 0;
		}//time out ping
		int plen=es.ES_enc28j60PacketReceive(BUFFER_SIZE,buf);
			//we idle here
		if(!es.ES_client_waiting_gw()){ //got arp reply
			return 1;

void shutdown_ups(){
        //get time from rtc clock
        DateTime now = RTC.now();
        int hour=now.hour();
        int minute=now.minute();
        //execute shutdown only after 1700
        if (hour>=15)
          if (minute>=30){

float get_temp(){
	byte i;
	byte present = 0;
	byte type_s;
	byte data[12];
	byte addr[8]={0x10, 0x28, 0xC, 0xBB, 0x0, 0x8, 0x0, 0xBE};
	float celsius;
	type_s=2; //ds18s20
	ds.write(0x44,1); // start conversion
	present = ds.reset();
	ds.write(0xBE); // Read Scratchpad
	for ( i = 0; i < 9; i++) {data[i] = ds.read();}
	// convert the data to actual temperature
	unsigned int raw = (data[1] << 8) | data[0];
        raw = raw << 3; // 9 bit resolution default
	if (data[7] == 0x10) {
		// count remain gives full 12 bit resolution
		raw = (raw & 0xFFF0) + 12 - data[6];
	celsius = (float)raw / 16.0;
	return celsius;

boolean get_ntp_time(){
   uint32_t endtime,d;
   boolean stat=false;
  uint16_t timeout=3000; //timeout ping after 2 seconds
  uint16_t dat_p;
  uint16_t clientPort = 123;
  char dstr[4];
  int sec = 0;
  int plen = 0;

  // Get IP Address details

  // Main processing loop now we have our addresses
  while(1) {
    if(millis()-endtime>=timeout){return false;}
    // handle ping and wait for a tcp packet
    dat_p=es.ES_packetloop_icmp_tcp(buf,es.ES_enc28j60PacketReceive(BUFFER_SIZE, buf));
    // Has unprocessed packet response
    if (dat_p > 0)
     uint32_t time = 0L;
      if (es.ES_client_ntp_process_answer(buf,&time,clientPort)) {

          if (time) {
          time -= SECONDS_FROM_1900_TO_1970; //calculate no of seconds after 2000
          time +=19800; //add offset of +5hr 30 min for IST (Indian Standard Time)
          DateTime now(time);
          DateTime RTC_now = RTC.now();
          //sync RTC to NTP
          return true;

      if (stat==false){

      if (set_mac(ntpServer))

      es.ES_client_ntp_request(buf,ntpServer,123);}//reset timeout counter


boolean set_mac(uint8_t *remIP){
  uint32_t endtime,dat_p;
  uint16_t timeout=3000; //timeout ping after 500 milli seconds
      if(millis()-endtime>=timeout){return false;}//timeout ping
       int plen=es.ES_enc28j60PacketReceive(BUFFER_SIZE,buf);
       if(dat_p==0) {
          // we are idle here
          if (es.ES_client_waiting_gw() ){

        if (!es.ES_client_waiting_gw() ){return true;}


Ishan Karve

About Ishan Karve

Ishan Karve is just an every day normal guy next door who happens to be an Electronics Engineer by profession and dabbles with PHP, Javascript, C++ and python. His interests vary as seasons change.. they change from astronomy to soul searching. This site is just a reflection of what he does to keep his mind engaged when he is not occupied by work and family. He is an extremely objective guy and is always ready for some good arguments.. of course over a glass of 40% proof alcohol.
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22 Responses to APC UPS Shutdown Manager

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  5. Andrew says:

    This is stupid. An APC network management card costs $60 or so off eBay, drops into your UPS management card slot right off the bat and has all this functionality and more, such as email alerts when power goes out, scheduled powerup and powerdown, etc.

    I appreciate what you’ve done here but it’s still stupid when an off-the-shelf solution exists, works more effectively, and has far more functionality.

    • Ishan Karve Ishan Karve says:

      Hi Andrew,
      I was expecting this comment , but then APC network management card is $60…. This stuff is $40… Money aside.. For me it was more of a ‘project’ rather than a ‘task’.
      Though the network management card is a no-nonsense solution, the amount of knowledge gained and bit of hard currency money saved tilts the balance in its favour.


  6. ejonesss says:

    sorry for the double post a hickup happened on my end that caused a page reset.

    have you ever thought of connecting up a car battery or even paralleling multiple batteries so you can get many hours or even days of run time?

    with extra runtime you can then just unplug the ups (conforming to the office rules) and still keep the server on.

    if your server is on a laptop you can get one of them car laptop power supplies and connect 2 car batteries in parallel so you can run the server during avery long weekend/holiday

    above works if it unattended power usage they are worried about.

    if it security that they are worried about ( un authorized access to the server during the off hours and the admin not knowing it and being able to do anything about it) they could.

    1. connect an alarm that alerts the admin by phone or email of hacking attempts.

    2. put all the server operations on a hosting provider passing the liability to someone else

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  10. John says:

    Im sure it’s about a fire hazard instead of network attacks or wasting energy.

  11. Mike says:

    Just curious, have you ever had a server catch on fire?

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  13. Tim says:

    Just leave to UPS and/or servers on. We had a massive UPS and 12 servers in one room, on 24/7 for 6 years and never had a fire.

    However as a maker/tinkerer I can appreciate why you went to the effort of creating the system, especially if it was on works time. However it is pretty over kill for your needs. Not to mention servers regularly don’t want to shutdown sometimes which will of course mean that the UPS will stay on over night.

    I think you did it the wrong way around to start with. Assuming the UPS gives enough time to shut down all the servers, just set a timer or manual switch on the UPS and let the UPS software on the servers shut them down. Or shut down the non-essential servers early using some sort of scheduling service.

    Failing that, why didn’t you just plug a usb cable into each server and measure the 5 volts. When they go low it is safe to assume that the server is off. Then when x servers are shut down, turn off the UPS.

  14. Ryan Gibson says:


    It seems this post is so good that it actually crashed your server 🙂 Great detail. Do you have an email I can catch you on? Have a few questions to ask.



  15. lyn says:

    hi sir.
    can i use this for my project?
    i’m planning to implement it to our school’s computer laboratory
    thank you ^_^

  16. Tony says:

    hello , may i ask how you were able to communicate with the ups via rs232 cable? Like how do you shut it down with hyperterminal? The commands used and the model of UPS that is compatible? And how you wired it to the arduino? We have a design project and we still cant move forward because of these questions. thank you

  17. Chris says:

    Hi Ishan,

    Are you using an APC SMT2200? I am trying to connect to this device via RS232 and am running into lots of trouble. From some research on the web, it seems as though having a network management card is necessary to connect to the device via RS232 without using PowerChute. Do your APCs have these cards, or were you able to talk to your APC via RS232 straight out of the Box?

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