ESP8266 Community Forum

- Fri Apr 03, 2015 6:42 am #13340 I was asked if MCP9008 Temperature sensor can be replaced with the cheaper and widely available LM75 one.
The answer is YES, it can be done without any problems, actually they can share same slot on CBDB Dev Board without any hardware changes as pin compatible, just choose your desired I2C address with the A0, A1, A2 pins.

More details : http://www.esp8266-projects.com/2015/04 ... -cbdb.html

ESP8266 MPDMv4 AC MAINS Dimmer Home: http://esp8266-projects.com/2016/04/mpdmv4-mains-dimmerswitch-html/
Available on Tindie: https://www.tindie.com/products/nEXT_EVO1/universal-ac-mains-dimmer-mpdmv41/

- Thu May 07, 2015 1:53 pm #16827 As you’ve mentioned that we can replace this sensor with LM75, I guess that won’t be tough since both have the same mode of temperature sensing. However, since you’ve already used both, could you please let us know about the accuracy of these sensors? I was wondering if they can be accurate up to 0.1K. I’ve been using LM185, not satisfied though. The output of this sensor is sometimes noisy tough, specifically at higher temperatures.

circuit board manufacturing

Last edited by pedro on Mon May 11, 2015 2:21 pm, edited 1 time in total.

- Thu May 07, 2015 2:56 pm #16835

As you’ve mentioned that we can replace this sensor with LM75, I guess that won’t be tough since both have the same mode of temperature sensing. However, since you’ve already used both, could you please let us know about the accuracy of these sensors? I was wondering if they can be accurate up to 0.1K. I’ve been using LM185, not satisfied though. The output of this sensor is sometimes noisy tough, specifically at higher temperatures.

LM185 is not an adjustable band-gap voltage reference diode?

If you stay under 100°C, you can have, in terms of accuracy:
- under ±0.35°C - MCP9808
- arround ±2/±2.2°C - LM75

Over 100°C (max temperature 125°C):
- ±1°C - MCP9808
- ±3°C - LM75

They are many factors than can influence badly reading process, from power supply to decoupling and PCB design. Overall MCP9808 is clearly better than LM75, and, off course, more expensive.

If you need even higher temperature measurement, one of the circuits suitable for high precision temperature measurement is a Wheatstone bridge with an NTC thermistor used as one bridge leg. Depending on your range you nedd to do some linearizing of the R/T characteristic and/or use lookup tables.
Another solution is a thermocouple based one. But in this case you need cold junction compensation. In goes up to +1000°C

What is the desired temperature range ?

ESP8266 MPDMv4 AC MAINS Dimmer Home: http://esp8266-projects.com/2016/04/mpdmv4-mains-dimmerswitch-html/
Available on Tindie: https://www.tindie.com/products/nEXT_EVO1/universal-ac-mains-dimmer-mpdmv41/