T C
4+
DC
−
fan
DC
+
Figure 5: A flyback diode across the motor.
motor, connecting a DC power supply is required. If not, this is optional - the
TC4+ and Arduino could alternatively be powered by USB.
The DC power supply should match the voltage of the DC motor. That is, if
your motor needs 20V, choose a 20V PSU. The rated current of the PSU must
match or exceed the power draw of the motor. If the motor draws 2A, choose a
PSU that is rated for at least 2A. The voltage of the PSU should also be within
the range of the on-board voltage regulator, which is 7-28V. If you need more
for your motor, replace the voltage regulator with an appropriate model.
Connect the power supply to the DC in screw terminal. Take care of correct
polarity: Positive goes to VIN, negative goes to GND.
3.4
Connecting to a DC motor
You can connect a DC load, like a fan motor, to the DC OUT terminal.
Important:
You must also connect a suitable flyback diode. That is, a diode
that is connected across the motor terminals, in opposite direction to usual
current flow. See Figure 5. This is to prevent damage to the MOSFET. Either
solder an appropriate diode to the motor (preferred), or screw it into the screw
terminal together with the motor power cables. (Be careful of correct polarity,
or you will create a short!) Make sure the diode is rated appropriately. If your
motor was originally connected to a bridge rectifier, you might want to reuse
one of the diodes from the rectifier.
Important:
DC motors can generate a lot of electrical noise, which can affect
thermocouple readings among other things. If your motor came with capacitors
or inductors connected to it, leave those in place, and connect the TC4+ to the
entire motor circuit. If you sourced a plain motor, take appropriate steps to
filter out noise.
3.5
Connecting a heating element
The TC4+ has two SSR drivers which can be used for heating elements. You
will need a DC-AC solid-state relay. Connect the DC side to OT1, taking care
of correct polarity. Connect the AC side of the SSR to the LIVE AC line going
to the heating element.
Important:
If your popcorn machine came with a thermal fuse, make sure this
stays connected in series with the heating element. If it didn’t come with one or
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