Related
Recommended
Engagement
  • Author Author: tariq.ahmad
  • Date Created: Date Created
  • Last Updated Last Updated:
  • Views 27829 views
  • Likes 9 likes
  • Comments 11 comments

DIY AC Dimmer Circuit: Control Your Lights with a Raspberry Pi Pico -- Episode 602

Dimmer circuits consisting of Phase Angle Control are used to efficiently adjust the AC power delivered to the AC loads by controlling the conduction angle. In this episode, Surbhika developed such a circuit to enable dimming of commonly used AC lights bulbs at home. This was an interesting DIY project as it meant realizing one of the fundamental concepts in power electronics and control theory to generally usable hardware.

Watch the Video:

Bonus Content:

image image

Bill of Materials

Product Name Manufacturer Quantity Buy Kit
RASPBERRY-PI Raspberry Pi Pico Board, RP2040, 32 bit, ARM Cortex-M0+ RASPBERRY-PI 2 Buy Now
MULTICOMP PRO TERMINAL BLOCK EUROSTYLE, 2 POSITION, 26-16AWG MULTICOMP PRO 5 Buy Now
ONSEMI Optocoupler, Triac Output, DIP, 6 Pins, 5.3 kV, Non Zero Crossing, 400 V ONSEMI 1 Buy Now
VISHAY Optocoupler, Transistor Output, 1 Channel, DIP, 4 Pins, 50 mA, 5.3 kV, 160 % VISHAY 1 Buy Now
WEEN SEMICONDUCTORS Triac, 800 V, 16 A, TO-220AB, 1.5 V, 170 A, 45 mA WEEN SEMICONDUCTORS 1 Buy Now
BOURNS LINEAR POTENTIOMETER, 10KOHM, 20%, 50mW BOURNS 1 Buy Now
PHILIPS LIGHTING LED Light Bulb, Reflector, GU10, Warm White, 3000 K, Dimmable, 36° PHILIPS LIGHTING 1 Buy Now
ETERNA GU10 Lampholder with Flying Leads ETERNA 1 Buy Now
LEDVANCE LED Light Bulb, Reflector, GU10, Daylight White, 6500 K, Not Dimmable, 36° LEDVANCE 1 Buy Now
 

Actions

  • May be a good solution would be to use a 12 volt lamp run from a mains transformer as the load. In this case there would be no issues with electrical safety. As an alternative may be you should use an opto-triac (eg CT3021) to trigger the main triac. This would then provide the requisite electrical isolation   when using a mains driven light bulbs. I believe that there are a number of assembled boards on the market (eg  RobotDyn) but be AWARE that some of them do not have the required mains isolation between pcb traces.
    Perhaps an interesting extension would be to use the Pico PIO circuits to control the triac firing so that the Pico could get on with other things (like measuring the local temperature or light levels) and working remotely over WiFi using (say) one of the new ESP8285 modules (or even the Pico W) .
    Just some ideas. 

  • I just came across this, and a while ago i was trying something like this. i ended having to use an arduino because i was having trouble with the interrupts on the pi pico. I see the code is no longer available, could you upload it again please? I want to see how you did it, and if you used interrupts or some other way. thank you!

  • The subject is interesting (although some discussion of EMC issues would be helpful) but the bench practice is life threateningly dangerous. Main voltages should never be applied to a breadboard operated on an open bench. No ifs, no buts, never.

    If you must use breadboard it should be enclosed in a protective enclosure, ideally with a mechanically linked mains ciruit breaker.

    A USB cable should never be connected directly to mains powered devices (live or neutral, doesn't matter). You have an opto-coupler but plugged into breadboard it gives no safety protection at all so in effect the USB cable is directly connected to mains.

    It is very important to set a good example in videos of this type because they are watched by a great many very inexperienced people.

    The warning at the beginning is no use if it is then ignored in the rest of the video.

    I think you should re-work this video to demonstrate safe practice.

    The obvious way to that would be to put the mains voltage parts on a separate board with adequate clearances and enclose that.

    if you need to probe the live circuit it gets harder.

    For bench work you should use a mains isolating transformer or, at the very least, an RCB (Residual Current Breaker) and suitable scope probes.

    An MCB won't save you - it has to pass the load operating current which will be more than enough to kill you.

    MK

  • in reply to Jaganhalo

    We have all been there when MCB saved the day. Yeah now that you have said it, I 'm realizing I should have mentioned this. But there were not many components in the circuit and i was doing all the measurements with respect to neutral terminal only. So it didn't make any difference even if I used differential probe.

  • Once I probed an AC test point with Oscilloscope and let's just the MCB saved the day, I see you are using some tool. Is it a differential Probe?
    It would be nice if you highlighted this, not a lot of people know that the Oscilloscope Neutral and earth are shorted internally.

  • in reply to Workshopshed

    No the optocoupler IC does the isolation.

    I see the confusion arises due to the improper symbol of SFH628A. Thanks for pointing that out! It should be like this (as given in the datasheet): image

  • The circuit diagram for the zero crossing looks like you have the AC supply connected to the microcontroller. Is that actually the case as it looked different on the breadboard?