0
\$\begingroup\$

I have been trying for a long time to digitally control the fan speed and light intensity of a dimmable LED bulb, but I am not able to. Basically I want to replace the mechanical potentiometer with a digitally controlled resistance. I have tried every possible dimming solution.

  1. Replacing the mechanical pot with LDR and varying its resistance by illuminating it with LED in closed tube. It's not at all a good & stable solution and the arrangement is difficult to replicate (the output fluctuates greatly).(commercially available solution is very costly)

  2. Cutting a portion of AC waves by detecting zero crossing with the help of a micro (ATTiny). It gives a flickering output when a dimmable LED bulb is used.

  3. Thought of digital potentiometer arrangement, but the voltage that comes across the mechanical potentiometer in a triac dimmer circuit is around 180V when the pot's at the highest resistance level of 300KOhm (The AC supply voltage in my country is 240V). It is well above the digital pot's max recommended voltage of 5V (Vdd) across the variable resistance legs. Can anyone suggest a digital pot that can be interfaced with a 5V micro and can withstand the voltage in a triac dimmer circuit. Is there any other solution to digitally control a resistance. I am willing to achieve this within 3$.

Is there any other better way to do it? Please help.

\$\endgroup\$
  • \$\begingroup\$ Please post an image of the waveform created by method #2. \$\endgroup\$ – Jon Feb 13 '15 at 7:45
1
\$\begingroup\$

Solution 2 should have worked, I think you've implemented it incorrectly. This is what I would try: Where I live there are dimmers with a rocker switch (a pair of push buttons actually). See if you can get one, open it and check the voltage across the button (be careful). If it's low try to short it with an active device like a transistor. If it works add a micro to control the transistors.

\$\endgroup\$
0
\$\begingroup\$

If you want to control this with a 5v micro signal you first need to use an opto-coupler (look it up). You don't want the high voltage in anyway getting back into the micro circuitry. With this you can send pulses in a PWM method (look it up) to control the high voltage side of the fan and even the light (using one opto-coupler circuit for each). There are even opto-couplers available with triac outputs already built in, (you might be able to connect this type of part right up to the existing triac circuit). Sync'ing it to the line signal helps too. You need to check the spec on the LED bulb to see exactly what type of dimmer it works with. (Because commercial LED HV bulbs are still new there are not yet common methods for dimming these.)

You can also go to the hardware store and buy a ready made remote fan/light controller, only about US$22 here in the states. Likely similar 240vac parts available if that's your line voltage. If you want you likely could hook up the remote wiring to you micro signals. See link for a US type of controller: http://www.amazon.com/Universal-Ceiling-Fan-Remote-Control/dp/B001I1M95E

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.