Imported-Repos/ATmega-Soldering-Station
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@@ -52,7 +52,7 @@ Choose a power supply with an output voltage between 16V and 24V which can provi
# 3. Temperature Measurement and OpAmp Considerations #
A thermocouple (temperature sensor) is located in the T12 soldering tip. It creates a very small voltage depending on the temperature difference between the hot end and the cold junction (about 40 microvolts per degree Celsius). To measure this, the heater must be switched off since both share the same connections. The low voltage is amplified by the OpAmp and measured by the ADC of the microcontroller. The LMV358 is a very cheap and versatile OpAmp, but not the ideal choice for this task because it has a fairly high input offset voltage and is quite noisy. Although the SolderingStation also works with this OpAmp thanks to the software's smoothing and calibration algorithms, I highly recommend spending a little more money in a better one. The OPA2330AIDR for instance has the same pinout and can also be used with this board. It provides significantly more accurate and stable temperature measurements.
A thermocouple (temperature sensor) is located in the T12 soldering tip. It creates a very small voltage depending on the temperature difference between the hot end and the cold junction (about 40 microvolts per degree Celsius). To measure this, the heater must be switched off since both share the same connections. The low voltage is amplified by the OpAmp and measured by the ADC of the microcontroller. The LMV358 is a very cheap and versatile OpAmp, but not the ideal choice for this task because it has a fairly high input offset voltage and is quite noisy. Although the SolderingStation also works with this OpAmp thanks to the software's smoothing and calibration algorithms, I highly recommend spending a little more money in a better one. The OPA2330AIDR or OPA2333AIDR for instance have the same pinout and can also be used with this board. They provide significantly more accurate and stable temperature measurements.
![SolderingStationV2_LMV358_Noise.png](https://image.easyeda.com/pullimage/Q1peGd04fhp8kQzYYe6WfFqgOCv8MpL39cS0y2rr.png)
![SolderingStationV2_OPA2330_Noise.png](https://image.easyeda.com/pullimage/w2mQcD786pNi5hLEd5bqK2hezrsrUUhtttMRZYih.png)