Torque Sensor Board; Thermistor - Bunn ULTRA Technical Training Manual

Torque Sensor Board
The motor pin and auger shaft pin rotate between the LED (red) and photo transistor on the board, interrupting the
infra red beam. The microprocessor calculates the distance between the pins and determines the refrigerant solenoid
shut off point based on the programmable "thickness" setting per side.
Troubleshoot the torque board by blocking
and unblocking the infra red with an object
while monitoring with a voltmeter. If the meter
displays 5vdc when blocked and 0vdc when
unblocked, then the Torque Sensor is good. If
there is no 5vdc reading, verify that both red
and white sensors are clean.
Blocked – 5 vdc
Unblocked – 0 vdc

Thermistor

The thermistor or temperature sensors are
located inside the top rear of the cooling drum.
The resistance value changes according to
barrel temperature which correlates a change
in voltage. The "Temp and Torque" screen can
be used to see barrel temperature. The thermistor can be checked by resistance or voltage. Connect a voltmeter,
across the two leads of the temperature sensor (leave plug connected);
The indication must be:
a) Approx. 1.4 vdc @ 71° F
b) Approx. 2.6 vdc @ 32° F
If voltage reading is 0v, the Control Board is not supplying the necessary 5v and should be replaced. If the reading
stays at 5vdc, replace thermistor.
Resistance Check
Disconnect the plug on thermistor leads and check resistance as indicated below.
The indication must be:
a) 5650 ohms @ 32° F ± 10%
b) 2000 ohms @ 77° F ± 10%
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