User Tools

Site Tools

Trace:

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
istatrol [2016/03/25 16:41]
Traumflug [RADIATOR_RESPONSE_TIME]
istatrol [2016/03/26 15:21]
Traumflug [Bugs]
Line 86: Line 86:
 {{ :​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.}}
  
-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.
  
 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.
Line 171: Line 171:
   * Replacing the ATtiny2313 with an ATtiny4313. Program memory is so constrained that this is considered to be a bug.   * Replacing the ATtiny2313 with an ATtiny4313. Program memory is so constrained that this is considered to be a bug.
   * C3, 1.0 uF, should have a 200\_mil wide footprint. Many suppliers don't have 100\_mil types at this capacity.   * C3, 1.0 uF, should have a 200\_mil wide footprint. Many suppliers don't have 100\_mil types at this capacity.
-  * Key //Menu// should go to INT1 to allow triggering an interrupt. Crucial for allowing the MCU to sleep.+  * Key //Menu// should go to INT1 to allow triggering an interrupt. Crucial for allowing the MCU to go to sleep.
   * These three thermistor connectors actually don't work this way. Connecting to means that current flows partially not to the measuring capacitor, but to the other ATtiny pin. Can likely solved with diodes, but note that a capacitor fills reasonably linear in the lower 20%, only.   * These three thermistor connectors actually don't work this way. Connecting to means that current flows partially not to the measuring capacitor, but to the other ATtiny pin. Can likely solved with diodes, but note that a capacitor fills reasonably linear in the lower 20%, only.
  
istatrol.txt ยท Last modified: 2018/05/27 16:10 (external edit)