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Assuming I send a signal wirelessly to a receiver connected to a fan. if the receiver detects that a pulse is there, it switches on the fan. the fan should stay on until it detects another high pulse, then it should switch the fan off thereafter. How could I make this happen?

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    \$\begingroup\$ Tried a 1-bit counter? \$\endgroup\$ – Ignacio Vazquez-Abrams Sep 3 '14 at 4:28
  • \$\begingroup\$ This is not a high frequency control, right? ie, you are NOT using this as a PWM for speed control, this is just ON/OFF in the 'wall switch' sense, correct? \$\endgroup\$ – NateFisher Sep 3 '14 at 18:04
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Maybe a D Flip Flop? Tie the /Q to D and then the clock becomes your input. Each pulse (rising edge) should toggle the Q output pin state. That pin can then control a relay/FET/whatever to gate your fan.

Good luck!

schematic

simulate this circuit – Schematic created using CircuitLab

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    \$\begingroup\$ Most FF's come with complementary outputs too! you may not need an inverter. \$\endgroup\$ – placeholder Sep 3 '14 at 5:13
  • \$\begingroup\$ this is good bcoz i have a bunch of dffs, why i handn't thought of it \$\endgroup\$ – user124627 Sep 3 '14 at 8:11
  • \$\begingroup\$ @placeholder correct. I could not find that schematic symbol in CircuitLab unfortunately, but yes, this should be a single IC solution. \$\endgroup\$ – NateFisher Sep 3 '14 at 18:03
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If you use a latching relay on the fan end, it can latch on a high pulse, then "un-latch" on the next high pulse. You will have to check the relay datasheet to be sure the length of the pulse is long enough to latch/unlatch, and that the voltage and current requirements are met for the relay coil latching.

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  • \$\begingroup\$ +1: The other answers aren't wrong, but since the request is to control a fan, a relay is probably the simplest choice. \$\endgroup\$ – Mario Vernari Sep 3 '14 at 6:59
  • \$\begingroup\$ thankyou, i was also thinking of latching it but wasn't knowing how it would work, thanks \$\endgroup\$ – user124627 Sep 3 '14 at 8:10

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