Most ceiling fans come with a remote control transmitter/receiver pair. The transmitter is hand-held or wall-mounted, and the receiver is installed in the ceiling box. Input to the receiver is a 2-wire circuit from the house wiring (neutral & hot, white & black) and output is white/black/blue, that is, neutral plus hot for the fan and hot for an optional light.

My question is, how does the receiver work, specifically the reverse function ? The light control is probably just a triac like an ordinary light dimmer, and the fan speed is likely controlled using switched capacitors (as described in How do ceiling fan controllers work?). The mystery to me is, how does reversing the fan direction work ? (Some fans include a reverse switch on the fan motor itself, but many do not, so the remote receiver must somehow accomplish this). I doubt it reverses the neutral and hot connections to the fan motor (I don't see how this would work, and it may violate code). Does it somehow send a code to some logic in the fan motor ?

Note (as pointed out below), this question really boils down to: how do you reverse a ceiling fan motor using only the two wires going to it ?

  • \$\begingroup\$ At a complete guess, with no knowledge of the system at all, it might use a single-phase synchronous motor, of the type that runs in a random direction each time it starts up. By blocking the motor's rotation, one can get it to switch directions. \$\endgroup\$ – Hearth Jul 23 '18 at 18:23
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    \$\begingroup\$ This question boils down to how do you reverse a ceiling fan motor. It has nothing really to do with remote control or its receiver if you think about it. \$\endgroup\$ – Andy aka Jul 23 '18 at 18:28
  • \$\begingroup\$ That's technically true, Andy. But if one has a separate switch, it could switch between different windings in the motor (I'm very ignorant on motors). With the remote, it has to happen using only two wires from the remote rx'er to the fan motor assembly: the neutral and the black. But you're right, it's not necessarily remote. So I guess I'd say "how do you reverse a ceiling fan motor that has only two wires going to it ?" \$\endgroup\$ – RustyShackleford Jul 23 '18 at 18:43
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    \$\begingroup\$ Low-cost after-market add-on remotes typically can't adjust direction (or even speed). They're just on-off controls. Remote receivers which are built into the fan can reverse direction my reversing one of the windings and adjust speed by switching in different capacitors. \$\endgroup\$ – brhans Jul 23 '18 at 18:51
  • \$\begingroup\$ Possible duplicates: electronics.stackexchange.com/questions/330308/… electronics.stackexchange.com/questions/213008/… \$\endgroup\$ – Solomon Slow Jul 23 '18 at 18:54

The motor itself has more than two wires going to it. By reversing one pair you can reverse the motor. Here is a typical ceiling fan internal schematic (including light, reversing switch and speed control)- it's a split-phase motor with a run capacitor:

enter image description here

The reverse function from a remote control is probably accomplished with a DPDT relay (or perhaps multiple SPDT relays).

For the answer to how it is done over two wires, see US patent #4,719,446 These are about the remote control function rather than specifically the reversing.

enter image description here

  • \$\begingroup\$ Second answer here appears to be relevant: electronics.stackexchange.com/questions/356941/… \$\endgroup\$ – Spehro Pefhany Jul 23 '18 at 19:26
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    \$\begingroup\$ See also US719446 These are about the remote control function rather than specifically the reversing. \$\endgroup\$ – Spehro Pefhany Jul 23 '18 at 19:27
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    \$\begingroup\$ US Patent 719446 describes a method for doing just what was asked: how can the direction (and speed) or a fan motor assembly be controlled by only two wires. Basically, the remote receiver tweaks the AC waveform on the two wires leading to the fan motor assembly. These slight modifications of the AC waveform are interpreted by a microprocessor within the fan motor assembly. That microprocessor controls the various windings in the fan motor which control speed and direction. \$\endgroup\$ – RustyShackleford Jul 25 '18 at 16:57

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