LM35DZ not working with MCP3208 on raspberry pi 3

Question

Situation

I wanna measure the temperature using LM35DZ on raspberry pi 3.

I'm using MCP3208 ADC. And since the other analogue sensors (eg. flame sensor..) are working normally, I have no problem with MCP3208.

Problem

But LM35DZ are not working with MCP3208, the outputs are always 0.

Here are my code with nodejs, a circuit and a pin map.

Code

var mcpadc = require('mcp-spi-adc');
var pigpio = require('pigpio');

function analogRead(channel) {
    return new Promise((resolve, reject) => {
        var sensor = mcpadc.openMcp3208(channel, (err) => {
            if (err) reject(err);
            sensor.read((err, reading) => {
                if (err) reject(err);
                resolve(reading);
            });
        });
    });
}

var Gpio = pigpio.Gpio;
var lm35;
var iv;

iv = setInterval(() => {
    analogRead(7).then((value) => {
        console.log(value);
    })

}, 300);

Result

...
{ rawValue: 0, value: 0 }
{ rawValue: 0, value: 0 }
{ rawValue: 0, value: 0 }
...

Circuit

sorry for my poor painting skills..
MCP3208 Din is not connected directly to GND.

And I add voltage divider on connection between MCP3208 Din and Pi MISO because someone said I must not put 5V signal into Rpi.

My Circuit and code are working well with the other sensors, but not working on LM35DZ.

Answer 1

Have you confirmed communication is working between the RPi and the MCP3208 in this configuration? If it IS working then skip the next paragraph and start checking for functionality.

Both the LM35 and the MCP3208 can run on 3V3. (Always look at the datasheets to confirm.) So first thing is loose the voltage divider you made as I suspect that is probably messing up your communication between the RPi and the MCP3208.

You should be checking the functionality of the system starting at the LM35. Get a volt meter and confirm the LM35 is giving you a voltage level on the DATA pin.

If the DATA pin has a voltage then you have an issue further up the line.

If you have other sensors attached and they ARE working then simply swap out the data line from another sensor for the LM35 and confirm you are still seeing a value on Ch7. If you are seeing a value then try a pull down resistor of around 18K Ohm or more.

If you don't see a voltage value then you have an issue with either the port or the code you are using to read that port.

I'd first see if changing the port[Channel] in your code fixes the problem. If it does then you know that the port is suspect and you should avoid using it. If it doesn't work then time for you to debug the code.

LM35-datasheet

MCP3208-datasheet