M-Labs/thermostat
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Reverse polarity of current through the TEC #82

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atse wants to merge 1 commits from atse:reverse-tec-polarity into master
pull from: atse:reverse-tec-polarity
merge into: M-Labs:master
Conversation 3 Commits 1 Files Changed 2 +4 -4
2 changed files with 4 additions and 4 deletions
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2
README.md
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@ -184,7 +184,7 @@ postfilter rate can be tuned with the `postfilter` command.
- Connect TEC module device 1 to TEC1- and TEC1+.
- The GND pin is for shielding not for sinking TEC module currents.
When using a TEC module with the Thermostat, the Thermostat expects the thermal load (where the thermistor is located) to heat up with a positive software current set point, and cool down with a negative current set point.
When using a TEC module with the Thermostat, the Thermostat expects the thermal load (where the thermistor is located) to cool down with a positive software current set point, and heat up with a negative current set point.
Testing heat flow direction with a low set current is recommended before installation of the TEC module.

6
src/channels.rs
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@ -118,7 +118,7 @@ impl Channels {
let center_point = self.get_center(channel);
let r_sense = ElectricalResistance::new::<ohm>(R_SENSE);
let voltage = self.get_dac(channel);
let i_tec = (voltage - center_point) / (10.0 * r_sense);
let i_tec = (center_point - voltage) / (10.0 * r_sense);
i_tec
}
@ -142,9 +142,9 @@ impl Channels {
};
let center_point = vref_meas;
let r_sense = ElectricalResistance::new::<ohm>(R_SENSE);
let voltage = i_tec * 10.0 * r_sense + center_point;
let voltage = -i_tec * 10.0 * r_sense + center_point;
let voltage = self.set_dac(channel, voltage);
let i_tec = (voltage - center_point) / (10.0 * r_sense);
let i_tec = (center_point - voltage) / (10.0 * r_sense);
i_tec
}