Talk:Freezer to Refrigerator Conversion

math

What temperature should a refrigerator be?

The FDA recommends between 32°F and 40°F (0°C to 4°C).

Energy Star recommends between 35°F and 38°F (2°C to 3°C) to reduce energy use.

thermister =

10K Ohm @ 25 celcius

20.13 @ 5

24.30 @ 0

voltage devider

Vout = (R2/(R1+R2)) x Vin

24.3 Ohm -> 0.962V

24 Ohm -> 0.97V

21 Ohm -> 1.06V

Analog to Digital Converter

Arduino's onboard ADC converts voltage to a range of 0-1023 based on arduino's base voltage

so on a 3.3V arduino, analogRead(A1) will equal

0V = 0 reading

1.65 = 511

3.3V = 1023

so

24.3 Ohm = 298.25 = 0 C

24 Ohm = 300.88

21 Ohm = 329.99

Relay Trigger Voltage

Arduino MKR 1000 is a 3V board. The Solid State Relay minimun trigger voltage is 3V. I had trouble getting the relay to activate. measured 2.8V. This was not enough to trigger. I changed the wiring to share a ground with the temperature. May need a diode? Sparkfun makes a 5V board. going to switch to that, but need to figure out where im losing the 0.2V.

• try using a pin to pull to ground?

MKR1000

could use 5V pin on MKR1000 to connect to the Relay (+) terminal, then pull to ground the relay's (-)

this might blow the pin oops. nvm