Thermocouple with 7-segment display

Thread Starter

slevesque

Joined Jan 31, 2023
43
I like the LPC824 because it has a built in 12-bit ADC. You can also implement a look-up table to determine the temperature from the resistance of a thermistor, which makes the sensor much cheaper than a thermocouple or a temperature sensor IC.

But if you have a single 7-segment display, how are you going to display temperatures between -10°C and +150°C on a single digit? That’s why we all thought you were making a bargraph.
Yes I will need more than 1 7-segment, probable 3 7-segment would be good. I will look at the LCP824 and will probably will go with that.
 

Ian0

Joined Aug 7, 2020
9,671
Yes I will need more than 1 7-segment, probable 3 7-segment would be good. I will look at the LCP824 and will probably will go with that.
Now you’ll need an LED driver because the LPC824 doesn’t have enough output pins to drive 24 segments, or you’ll have to multiplex it.
But now, you’ve decided on 3 digits, take a look at the ICL7106, so old that the data sheet is written in Latin, but still available. Carpe Diem.
 

MrSalts

Joined Apr 2, 2020
2,767
take a look at the ICL7106, so old that the data sheet is written in Latin, but still available. Carpe Diem.
That's the first chip that came to mind if he wants to directly link the ADC to the 3x7-seg display.
However, there are some 4x7-seg LED displays from companies like Adafruit that have a small I2C to LED driver chip mounted to them so he could control it by 2-wires serial ( plus supply and ground) if he wants to go the microcontroller route.

Just this week, I throw something together that controls a high power Lumiled LED that had an on-chip thermistor. I used a little I2C SSD 1306 driver in a 64x128 OLED display.
 

Thread Starter

slevesque

Joined Jan 31, 2023
43
That's the first chip that came to mind if he wants to directly link the ADC to the 3x7-seg display.
However, there are some 4x7-seg LED displays from companies like Adafruit that have a small I2C to LED driver chip mounted to them so he could control it by 2-wires serial ( plus supply and ground) if he wants to go the microcontroller route.

or
That seems to be a great idea. Using I2C would greatly reduce the amount of wire required. I will have to take a look at this, thanks.
 

KeithWalker

Joined Jul 10, 2017
3,063
There is a number of tutorials on the internet that show you how to make a thermometer using an Arduino micro with a DS1820 temperature sensor and an OLED display. You may have to tweak the Arduino C software to get the range you want. The parts are very inexpensive at AliExpress:
DS18B20 probe $2.00
Arduino micro $5.00
1.3" OLED display $4.00
Those prices are in Canadian dollars and include shipping. Those items and some connecting wire are all you need.
Here is one of the tutorials:

https://www.makeuseof.com/make-a-diy-digital-thermometer-with-arduino/
 

Reloadron

Joined Jan 15, 2015
7,501
No idea your location but I can buy a 20 X 4 LCD display with the simple I2C interface on Amazon for about $11.00 USD. HD44780 2004 LCD 20x4 2004A Character LCD Screen Display Module Blue Backlight with IIC/I2C Serial InterfaceAdapter . I can buy a complete easy program with code examples online . I can buy a knockoff Arduino Uno uC board complete ELEGOO UNO R3 Board ATmega328P with USB Cable(Arduino-Compatible) for Arduino for about $17.00 USD. I can buy SD18B20 sensors from Amazon for about $1.00 each. Temperature Sensor and EEPROM • Measures Temperatures from -55°C to +125°C (-67°F to +257°F) • ±0.5°C Accuracy from -10°C to +85°C • Programmable Resolution from 9 Bits to 12 Bits. So you lose a few degrees.

I would need a range of temperature from -10 degrees Celsius to 150 degrees Celsius. I will look at the LM35 and the LM3914 and see if I can figure out how it works.
You can't have that with a two digit display. If you want 150 Degrees C you need a 3 digit display and if you want 0.1 degree resolution that's a four digit display.

You can buy a complete temperature controller on Amazon for under $40.00 USD Inkbird PID Temperature Controller Kit, High Voltage 100ACV to 240ACV, Comes with SSR 40DA Solid State Relay, K Type Thermocouple, and White Heat Sink.

There are other pre made solutions available but seriously when all is said and done I believe buying an off the shelf solution will be the least expensive route to go. You also need to outline realistic uncertainty numbers (accuracy).


Ron
 

MrSalts

Joined Apr 2, 2020
2,767
You can get three of these small displays for $10. One in blue light, one in white light and one special one where the top 16 rows of pixels are yellow and the rest are blue. The special one lets you create a header that's a different color.
 

Thread Starter

slevesque

Joined Jan 31, 2023
43
Thanks all, I will use a basic uC with a thermistor. For the display I will tried to find something more convenient then a 7-segments display.

Your help was much appreciated
 
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