How to use thermistor and 8051 single chip and LCD to display temperature detection. Please answer

一百年后的自己

How to use thermistor and 8051 single chip and LCD to display temperature detection. Please answer [Copy link]

 

Please help me answer this question. I am a newbie and just started to learn microcontrollers.

btty038

It seems that there is a formula corresponding to the temperature slope. I have used it before, but it is not written by me. I am only expressing the meaning. How did the construction team do it? Please help me, experts.

一百年后的自己

btty038 posted on 2019-9-18 15:11 It seems that there is a formula corresponding to the temperature slope. I have used it but it is not written by me. I only express the meaning. How did the construction team do it...

OK, thanks

maychang

"How to use thermistor and 8051 single chip and LCD to display temperature"

Measuring temperature actually means giving a fixed current to the thermistor and measuring the voltage across the thermistor. This requires the use of the A/D inside the microcontroller or an external A/D. The value obtained by the A/D conversion read by the microcontroller is usually binary and needs to be converted into decimal before it can be displayed. The decimal data is stored in an area of RAM, and the microcontroller may also need to convert it into a format acceptable to the LCD before sending it to the LCD.

As for how often to measure the temperature, the timer inside the microcontroller must be used.

btty038

Myself a hundred years later posted on 2019-9-18 15:32 OK, thank you

I used LM50 without thermistor

一百年后的自己

maychang published on 2019-9-18 16:14 "How to use thermistor and 8051 single chip and LCD to display temperature" To measure temperature, actually give the thermistor a fixed current...

The table I posted is the temperature corresponding to the resistance. My chip should be 6V, 10 bits.

How to give a fixed current and how to use A/D?

huo_hu

NTC resistor, directly divide the voltage with resistor and then look up the table, the accuracy is slightly worse but the circuit is very simple

huo_hu

NTC resistors must be calibrated, even if they are from the same batch, the parameters are different, e exponential function, use matlab to generate data and put it into the program

一百年后的自己

huo_hu posted on 2019-9-18 16:47 NTC resistor, directly divide the resistor voltage and then look up the table, the accuracy is slightly worse but the circuit is very simple

It should be, resistor divider?

maychang

Myself 100 Years Later Posted on 2019-9-18 16:46 The table I posted is the temperature corresponding to the resistance. My chip should be 6V, 10 bits. How to give a fixed current, how to use the A/D? ...

How to give a fixed current?

There are many methods.

One method is to use a constant current source, which is more expensive.

One method is as mentioned on the 7th floor, resistor voltage division. Here, resistor voltage division means that a standard resistor and a thermistor are connected in series (obviously the current is equal), and the voltage is applied to the two resistors in series. First measure the voltage across the standard resistor to know the current, and then measure the voltage across the thermistor to know the resistance of the thermistor. In fact, as long as you compare the two measurement results, you can know the resistance of the thermistor.

一百年后的自己

maychang posted on 2019-9-18 17:01 There are many ways to "give a fixed current". One method is to use a constant current source, which is more expensive. Another method is...

This requires IIC, right?

huo_hu

The main problem is that the NTC resistance and ADC voltage do not completely correspond, that is, the low temperature point you want does not match 0V. The complete correspondence requires the op amp to do conditioning.

This mismatch results in a loss of precision for the ADC.

Cross-current source is also OK but it can't solve the above problem, and the data still needs to be looked up in the table.

huo_hu

The thermal effect of the NTC resistor must be considered when dividing the resistor voltage.

maychang

Myself a hundred years later posted on 2019-9-18 17:06 This requires IIC, right?

IIC is a communication format and has nothing to do with constant current sources.

huo_hu

Your table is meaningless. Each NTC needs to be calibrated before it can be used. It is troublesome to measure the B value and substitute it into the formula. This is why NTC is much cheaper than PT1000.

一百年后的自己

maychang posted on 2019-9-18 17:18 IIC is a communication format and has nothing to do with constant current source.

You are making it a bit complicated. I don't understand. I am just learning 51 single chip microcomputer and I just use LCD to display temperature. I will use a soldering iron to test it.

一百年后的自己

huo_hu posted on 2019-9-18 17:13 The main problem is that the NTC resistance value and the ADC voltage do not completely correspond, that is, the low temperature point you want and 0V do not match. The complete correspondence requires the op amp to do conditioning. ...

You are making it a bit complicated. I don't understand. I am just learning 51 single chip microcomputer and I just use LCD to display temperature. I will use a soldering iron to test it.

一百年后的自己

huo_hu posted on 2019-9-18 17:14 The thermal effect of the NTC resistor should be considered when dividing the resistor voltage.

It is a simple LCD and ADC to display the temperature, and then use a soldering iron to test it.

一百年后的自己

huo_hu posted on 2019-9-18 17:19 Your table is meaningless. Each NTC needs to be calibrated before it can be used. It is troublesome to measure the B value and substitute it into the formula. This is why NTC is faster than Pt100...

This is not the first time I learn 51 single-chip microcomputer, so I have to learn a little bit

huo_hu

Myself in a Hundred Years Published on 2019-9-18 17:20 You made it a bit complicated. I don't understand. I just started to learn 51 MCU and I just used LCD to display temperature. I will use electric soldering iron to...

Let's say, now suppose the temperature range you want to measure is 10~100 degrees, and the resistance value is 19.9~0.679K ohms. Can you output a voltage of 0~5V without an op amp circuit? 5V is the reference voltage of ADC