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  • nevyn.hira commented on ianvanmourik's instructable OPEN SOURCE AIR PURIFIER3 years ago
    OPEN SOURCE AIR PURIFIER

    Hey this is pretty amazingly cool. Have you considered swapping the relays out for an optoisolator (the fans would be rated at around 250mA? In which case use a 2N222 in a darlington pair like arrangement with a PC817 should give you what you need.)? This would not only remove the clicking from the relays BUT also allow you to control the speed of the fans via PWM rather than a variable resistor. This would have a couple of implications:* You'd use slightly less power i.e. you're not using power to heat in the variable resistor.** You could use the variable resistor as a sensor instead to control the PWM if you really wanted it there.* The code would need small changes as a consequence.* You could have various levels based on the level of dirty air from the gas sensor eliminating the ne...

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    Hey this is pretty amazingly cool. Have you considered swapping the relays out for an optoisolator (the fans would be rated at around 250mA? In which case use a 2N222 in a darlington pair like arrangement with a PC817 should give you what you need.)? This would not only remove the clicking from the relays BUT also allow you to control the speed of the fans via PWM rather than a variable resistor. This would have a couple of implications:* You'd use slightly less power i.e. you're not using power to heat in the variable resistor.** You could use the variable resistor as a sensor instead to control the PWM if you really wanted it there.* The code would need small changes as a consequence.* You could have various levels based on the level of dirty air from the gas sensor eliminating the need for the variable resistor entirely. i.e. the speed of the fans would be based on the dirtiness of the air rather than preference.

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