~~META:description abstract=Set of uC powered devices to monitor the house~~ microcontroller sensor web http power

Set of uC powered devices to monitor the house, including :

• Electrical power consumption
• Water consumption
• Temperature (inside/outside)

All compatible with collected datalogger.

• Electrical power measurement (main, heaters, water heater, server, box freezer, box main …)
• Water consumption sensor
• Inside and outside temperature monitor

The devices are to operate inside the home network, over TCP/IP protocol, HTTP was chosen for its easier debugging as well as its versatility.

The datalogger server is to fetch the data by itself, eg the sensors just have to implement a web server.

The sensors will expose data as plain ascii text.

Measuring power deals with measuring current as well as peak voltage (always a sine wave).

In the following subsections we are dealing with home-made CTs.

Document on Current Transformers

• No open-loop use
• The higher the turns the higher the quality
• Same goes with the impedance
• One should care not to saturate the core, keep a 30% current handling margin

Excitation current : , e is the output voltage (V), L is the inductance (H) and the result is in A/s This current should be at the very most equal to a 10^th of the minimum sample current.

Measured voltage : , R is the burden resistor (Ω), I_eff is the primary current and the result is in V.

In this case we just need a way to know whether the monitored device is powered or not. Simple apparatus like CT + rectifier + smoother + detector may be used.

In this case we are interested in the peak value of the current. CT + rectifier + well designed smoother will do.

Most complicate case since we need to get the RMS value of the current. CT + ADE7755 + constant voltage feed seems to be a good solution.

The main panel streams data about consumption by itself, only a few components are needed to get the data.

The water meter emits data on a regular basis using an open-source protocol, we just need a compatible receiver and the according spec.

Most simple data to gather, the only concern should be the sturdiness of the outdoor sensor.

Data exposure is done using the TCP/IP/HTTP stack from tuxgraphics, latest version is available here.

The device can be asked for individual named values or for a pipe separated list of all available named values.

Code should be as reusable as possible.

Example (WIP) :

main.c

#include <avr/io.h>
#include <stdlib.h>
#include <string.h>
#include "ip_arp_udp_tcp.h"
#include "enc28j60.h"
#include "timeout.h"
#include "avr_compat.h"
#include "net.h"
 
 
//static uint8_t mymac[6] = {0x54, 0x55, 0x58, 0x10, 0x00, 0x24};
 
// mac[4] = 0x01 : YHome device
// mac[5] = device id
static uint8_t mymac[6] = {0x40, 0x00, 0x00, 0x00, 0x01, 0x01}; // 0x01 : EDF, 0x02 : Box, 0x03 : Tmp
static uint8_t myip[4] = {192, 168, 0, 201}; // 201 : EDF, 202 : Box, 203 : Tmp ...
 
#define MYWWWPORT 80
 
#define BUFFER_SIZE 550
static uint8_t buf[BUFFER_SIZE+1];
 
 
#define N_MES 4
 
typedef struct {
	uint16_t ips; // count per sec
	uint16_t msp; // 100us per imp
	uint16_t cnt; // 100us counter
} Tmeasure;
 
volatile Tmeasure measure[N_MES];
volatile float sensorips[N_MES] = {139.123, 139.123, 139.123, 139.123};
volatile uint16_t tcnt = 0;
volatile uint8_t fetch = 0;
volatile float I[N_MES];
 
SIGNAL(##INT) {
	uint8_t ch = ##get_ch();
	measure[ch].ips++;
	measure[ch].msp = measure[ch].cnt;
	measure[ch].cnt = 0;
}
 
SIGNAL(TIMER0_COMPARE_A) { // Setup with compare
	TCNT0 = 0x00;
	uint8_t i;
	for(i=0; i<N_MES; i++) measure[i].cnt++;
	tcnt++;
	if(tcnt < 10000) return;
	// 1s elapsed
	tcnt = 0;
	fetch = 1;
}
 
void init(void) {
	cli();
 
	TCCR0A = 0x00;
	TCCR0B = 0x02; // P = 8
	OCR0A = 0x64; // 64 @ 8MHz, c8 @ 16MHz
	TIMSK0 = 0x02; // CMPA irq en.
 
	// set the clock speed
	CLKPR = (1<<CLKPCE);
	CLKPR = 0; // 8 MHZ
	_delay_loop_1(0); // 120us
 
	//initialize the hardware driver for the enc28j60
	enc28j60Init(mymac);
	enc28j60clkout(2); // change clkout from 6.25MHz to 12.5MHz
	_delay_loop_1(0); // 60us
	enc28j60PhyWrite(PHLCON, 0x476);
	_delay_loop_1(0); // 60us
 
	//init the ethernet/ip layer:
	init_ip_arp_udp_tcp(mymac, myip, MYWWWPORT);
 
	sei();
}
 
void printInt(uint16_t i, char *se) {
	while(i) {
		*se = 0x30 + (uint8_t)(i % 10);
		i /= 10;
		se--;
	}
}
 
void printI(float i, char *s) {
	s[0] = ' ';
	s[1] = '0';
	s[2] = '.';
	s[3] = '0';
	s[4] = '0';
	s[5] = '0';
	printInt((uint16_t)i, s+1);
	printInt((uint16_t)(i * 1000) % 1000, s+5);
}
 
void main(void) {
	uint16_t plen;
 
	uint8_t i;
	char *s[6];
 
	init();
 
	while(1) {
		if(fetch) {
			for(i=0; i<N_MES; i++) if(measure[i].ips > measure[i].msp) {
				I[i] = measure[i].ips / sensorips[i];
			}else{
				I[i] = 10000 / (sensorips[i] * measure[i].msp);
			}
			fetch = 0;
		}
 
		plen = packetloop_icmp_tcp(buf, enc28j60PacketReceive(BUFFER_SIZE, buf));
		if(plen == 0) continue;
		if(strncmp("GET ", (char *)&(buf[plen]), 4) != 0) { // head, post and other methods
			plen = fill_tcp_data_p(buf, 0, PSTR("HTTP/1.0 401 Unauthorized\r\nContent-Type: text/html\r\n\r\n<h1>401 Unauthorized</h1>"));
		}else if(strncmp("/ ", (char *)&(buf[plen+4]), 2) == 0) { // catch all
			plen = fill_tcp_data_p(buf, 0, PSTR("HTTP/1.0 200 OK\r\nContent-Type: text/plain\r\nPragma: no-cache\r\n\r\n"));
			for(i=0; i<N_MES; i++) {
				if(i) plen = fill_tcp_data_p(buf, plen, PSTR(" | "));
				printI(I[i], s);
				plen = fill_tcp_data(buf, plen, s);
			}
		}else if((&(buf[plen+5]) >= 0x30) && (&(buf[plen+5]) <= 0x39)) { // specific sensor
			i = &(buf[dat_p+5]) - 0x30;
			plen = fill_tcp_data_p(buf, 0, PSTR("HTTP/1.0 200 OK\r\nContent-Type: text/plain\r\nPragma: no-cache\r\n\r\n"));
			if(i<N_MES) {
				printI(I[i], s);
				plen = fill_tcp_data(buf, plen, s);
			}
		}else{
			plen = fill_tcp_data_p(buf, 0, PSTR("HTTP/1.0 401 Unauthorized\r\nContent-Type: text/html\r\n\r\n<h1>401 Unauthorized</h1>"));
		}
		www_server_reply(buf, plen); // send web page data
	}
}