Seestar Dew Heater Control: Page 2

Seestar Dew Heater Control

Misam

jpp_seestars50 U=RI => I=U/R, therefore when the temperature drops, the resistance drops and the current increases as the voltage is constant. The increased current increases the temperature of the heating element. Elementary school physics.

jpp_seestars50

Makes sense if that's how they manage the heating element by keeping the voltage constant. And in reverse, as the temperature increases the current would decrease and reduce the temperature of the heating element. Would ZWO confirm this please? This of course leads to the question, do they have a preset voltage they always use for the dew heater, say 5 volts?

Misam

jpp_seestars50 That would be nice to know. The above is of course just my common sense thinking out loud... :-)

Lilo

Thermal resistance is how easy the heat goes away from the optics to the outer air. Sorry, English is not my native language and probably I used wrong term.
As result with given heater power and this particular device you'll get some positive delta temp relative to the ambient air.

Misam

Understand now! Actually I was using a wrong term. I was referring to a thermistor. Anyway, I do not know whether such a component can be used in this case... But the theory applies!

jpp_seestars50

BTW, the Seestar does have a temperature sensor for the battery so it knows to stop charging when it gets too cold. So technically it could use that sensor as a feedback mechanism to adjust the current to the dew heater. Not saying they do use it for that purpose but they could. Will ZWO please respond if the Seestar does adjust the current or the voltage to the dew heater based on the outside temperature - whether that is being done via software control or by keeping the voltage at a constant level and allowing the current to change based on the resistance of the metal in the dew heater strap changing with temperature. Or does it just keep the current at 100% of its max value no matter what the temperature is outside?

Lilo

jpp_seestars50
Battery temp is not an air temp at all. Useless. They also have CPU temp, also useless for dew control application.

jpp_seestars50

It must know when the outside temp goes below 0 degrees C so it knows to stop charging the battery. Not sure that is necessarily the battery temp.

Lilo

jpp_seestars50
Sure it's battery temp. Third wire in bat connector is for thermistor. Because the battery is charged, not the outside air. And should not if it's cold.

jpp_seestars50

I get that it is monitoring the battery temp but is that all it uses to decide if it is too cold to charge it? Only if the battery temp goes below 0 C?

jpp_seestars50

Also the seestar_alp software does show a temperature value so some sensor on the Seestar does appear to know the temperature. Apparently that is the sensor temperature which should be at ambient temperature within 30 minutes. Again, does the Seestar use that temp to control the current or voltage to the dew heater band? We don't know unless ZWO responds to this thread with clarity.

Lilo

jpp_seestars50
For battery it's battery sensor to decide is it good to charge or not. Other sensors could be on pcb, CPU for instance. But they are useless, internal temp is always higher than outside air.

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