Fun with NTCs
I'm toying with WS2812B muti colored LEDs and wanted to do a "smart" thermometer with them. At first i used a DHT11/12 i2C temperator/humidity sensor, but they are far from perfect. They use the i2c bus (or a weird custom protocol) , the accuracy is far from good and they are not so cheap (2$). Then i realised : I'm using a bluepill with a fairly good ADC converter (as seen on the DSO shell series), let's directly use a NTC resistor. Good thing i had a broken hotend printer head from the i3, so i extracted the thermistor named '3950/100k' After looking around, here is what i've found : * The "3950" part is the beta coefficient , actually it is -3950 as it is a NTC * The 100k is the resistance at 25 degrees C The formula is Beta= TxTref x ln (Rref/R) / (T-Tref) which can be inverted as alpha= -beta / ln( Rref/R) Temp = alpha *(K+25)/(K+25+alpha) -K with K=273.15 So we have beta = -3950, Rref=100k, Tref=25...