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istatrol [2016/03/25 16:41] – [RADIATOR_RESPONSE_TIME] Traumflug | istatrol [2016/03/26 15:17] – [Temperature Sensors] Clarification. Traumflug |
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{{ :istatrol:istatrol_thermistor_readout.png?direct&300|Very coarsely measured readout of the developers thermistor.}} | {{ :istatrol:istatrol_thermistor_readout.png?direct&300|Very coarsely measured readout of the developers thermistor.}} |
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For the technical: ATtinys feature no Analog Digital Converter (ADC). But there is [[https://github.com/Traumflug/ISTAtrol/raw/master/data%20sheets/AVR400.pdf|Atmel Application Note AVR400]], outlining how to get analog readouts by using the Analog Comparator (ACO) anyways. Essentially, a capacitor is loaded starting at time zero, then the time measured (with 16-bit Timer 1) how long it takes to reach a constant comparison voltage. As the loading current goes through the thermistor, higher thermistor resistance ( = lower temperature) leads to a longer loading time and vice versa. This implementation is actually simpler than one using an ADC. | For the technical: ATtinys feature no Analog Digital Converter (ADC). But there is [[https://github.com/Traumflug/ISTAtrol/raw/master/data%20sheets/AVR400.pdf|Atmel Application Note AVR400]], outlining how to get analog readouts by using the Analog Comparator (ACO) anyways. Essentially, a capacitor is loaded starting at time zero, then the time this capacitor takes to reach the same voltage as a constant comparison voltage measured (with 16-bit Timer 1). As the capacitor loading current goes through the thermistor, higher thermistor resistance ( = lower temperature) leads to a longer loading time and vice versa. This implementation is actually simpler than one using an ADC. |
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As one can see by the coarse measurements done, this is linear enough for our purposes. The recorded pretty hefty hysteresis isn't a property of the thermistor or the ISTAtrol, it's an artefact of the measurement procedure. | As one can see by the coarse measurements done, this is linear enough for our purposes. The recorded pretty hefty hysteresis isn't a property of the thermistor or the ISTAtrol, it's an artefact of the measurement procedure. |
istatrol.txt · Last modified: 2018/05/27 16:10 (external edit)