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obniz Hardware and cloud specifications.

MQ7

High sensitve multiple gas sensor especially for carbon monoxide(CO).

If you are using just MQ7(not module), Then prepare load resistance around 2k ohm.

This sensor need pre-heating. To get stable output, wait for heat-up, minimum 2 minutes.

This library get analog voltage from a sensor. Output voltage will increase regarding gas level. When you need actual level (ppm), you should do calibrate the sensor and prepare a formula.

wired(obniz, { vcc, gnd, do, ao});

name type required default description
vcc number(obniz io) no   VCC or H on MQ7.
gnd number(obniz io) no   GND or H on MQ7.
do number(obniz io) no   digital out
ao number(obniz io) no   analog out
// Javascript Example
var mq7 = obniz.wired("MQ7", {vcc:3, gnd:2, do:1, ao:0});
await mq7.heatWait();
mq7.onchangeanalog = function(voltage) {
  console.log(voltage);
}

startHeating()

It start heating.

// Javascript Example
var mq7 = obniz.wired("MQ7", {vcc:3, gnd:2, do:1, ao:0});
mq7.startHeating();

[await] heatWait(sec: number)

It start heating and wait for a while.
You can update wait time.

name type required default description
sec number no 120 seconds for wait
// Javascript Example
var mq7 = obniz.wired("MQ7", {vcc:3, gnd:2, do:1, ao:0});
await mq7.heatWait();
mq7.onchangeanalog = function(voltage) {
  console.log(voltage);
}

onchangeanalog = function(voltage: number)

Specified function will be called every voltage change.

// Javascript Example
var mq7 = obniz.wired("MQ7", {vcc:3, gnd:2, do:1, ao:0});
await mq7.heatWait();
mq7.onchangeanalog = function(voltage) {
  console.log(voltage);
}

onexceedvoltage = function(voltage: number)

Specified function will be called only when a voltage exceed voltageLimit variable.

// Javascript Example
var mq7 = obniz.wired("MQ7", {vcc:3, gnd:2, do:1, ao:0});
await mq7.heatWait();
mq7.voltageLimit = 1.0
mq7.onexceedvoltage = function(voltage) {
  console.log(voltage);
}

voltageLimit = number

It define the level of onexceedvoltage call.

// Javascript Example
var mq7 = obniz.wired("MQ7", {vcc:3, gnd:2, do:1, ao:0});
await mq7.heatWait();
mq7.voltageLimit = 1.0
mq7.onexceedvoltage = function(voltage) {
  console.log(voltage);
}

onchangedigital = function(voltage: number)

This function only be called when do was specified at wired function.
do output high/low regarding output. It compared in a module.
This function will be called every change of do.

// Javascript Example
var mq7 = obniz.wired("MQ7", {vcc:3, gnd:2, do:1, ao:0});
await mq7.heatWait();
mq7.onchangedigital = function(value) {
  console.log(value);
}


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