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You are here: Home / Decorative Lighting (Diwali, Christmas) / 8 Function Christmas Light Circuit

8 Function Christmas Light Circuit

Last Updated on July 1, 2019 by Swagatam 33 Comments

A simple mains operated, transformerless 8 function Christmas light circuit can be made by using a single IC, a rotary switch and a few SCRs, let's learn the procedures in detail.

The circuit is based on a single chip UTC8156 which is internally preprogrammed to produce 8 unique selectable light effects across 4 numbers of connected AC/DC lamps.

Usually such multi-function light effect generators are based on microcontrollers and require some complex programming but this this is a ready made preprogrammed IC which can deliver interesting changing light patterns over 4 mains operated lamps.

Circuit Application Hints

The proposed 8 function Christmas light circuit as the name suggest can be used for decoration during festivals, for example in Christmas the circuit can be applied for decorating a Christmas tree, in other popular festivals such as in Diwali the same circuit can be used for decorating door entrances, balconies and so on.

The 8 light patterns specified in the IC are very unique and can be selected using a small rotary switch with a plastic knob, this is important because the entire circuit is directly linked with the mains and therefore not isolated from the mains current, due to this reason a plastic knob for the rotary switch becomes extremely important to avoid lethal electric shocks.

The following images show the basic functional and wiring details of the proposed 8 function Christmas light circuit.

Both the designs are basically the same, the first is based on the 18 pin IC, while the second one is configured using the 16 pin IC version.

multi-Function Christmas Light Circuit

How the IC Works

The pinouts of the IC on the left are designated with the "function" specs, which can be appropriately switched using a rotary selector switch whose pole can be seen connected with the ground or the negative line of the circuit for executing the selected function.

The circuit can be operated from any desired supply input source, as per individual preference, it can be operated from the mains 220V or from mains 110V input supply using the configuration depicted above, and also from any 5 to 24V AC/DC adapter unit.

The lamps must be rated as per the input supply used, meaning for 220V it should be 220V rated lamps, for 110V the lamps ought to be 110V rated, and for 24V it should be rated at 24V

For 220V and 110V operations the involved resistors and the capacitor might need to be changed appropriately as shown in the following table:

As per the specifications, the IC is able to operate even from supplies as low as 5V, which implies that the circuit can be possibly operated through a mobile charger.

About the SCRs

As can be seen in the diagram that the supply Vdd to the IC is substantially dropped through R1, which probably means that the current to the IC and for the SCRs could be very low, in the order of a few milliamps.

Therefore here the applicable SCRs could be the smaller ones which can work with 1 to 5mA gate current such as BT169, and hence the lamps would also need to be smaller in current, for example the 10 watt or smaller lamps.

However, according to me the circuit can be appropriately modified for handling high watt mains bulbs simply by reducing R1 to 100 ohms and operating the circuit using a 5V cellphone charger and replacing the SCRs with C106 type of SCRs.

But with the above case the bulb top rail will need to be connected to one of the mains input for example the phase, and the negative common rail of the circuit will be required to be connected with the neutral line.

8 Functions Light effect

The IC is specified to generate the following 8 different light effect patterns as per the position of the rotary switch within the stipulated selection pinouts

1) The IC continuously scans and randomly generates the 8 functions in a row.

2) In this position the IC generates a wave like effect on the connected lamps.

3) In this mode the lights are illuminated in sequence one after the other and shutting off in the same order.

4) The fourth selection gives rise to a slow-glow kind of flashing visual over the connected lamps

5) Here the lights are switched off and ON with a chasing and simultaneously flashing style.

6) A quick switch ON of the lamps but a slow-fade effect can be witnessed in this position

7) The 7th preference produces a twinkling flashing effect on the lamps quite resembling the stars on the sky.

8) In the last mode the lamps actually do nothing but light up solid ON which also sometimes becomes useful for certain decorative applications.

For using the above circuit with high watt AC lamps, the design could be modified in the following manner:

Courtesy: search.alkon.net/cgi-bin/pdf.pl?pdfname=utc/8156.pdf




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About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

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  1. Search Related Posts for Commenting

  2. George Parks says

    Hi Swag.

    I would like to connect 80 Leds in series in the circuit. How can I proceed by just adding them in series in the 4 lines.

    Thank you and kind regards

    Reply
    • Swagatam says

      Hi George,
      you can replace the lamps with 80 series LEDs on each line, and add a resistor in series with each line.
      You can calculate the resistor value with the following equation:

      R = S – LED FWD / LED current.
      S is the input supply voltage from mains. FWD is the total voltage drop across the 80 LEDs

      Reply
    • George says

      Thank you very much Swag. I really appreciate your blogs. the South African guy

      Reply
      • Swagatam says

        It’s my pleasure George!

        Reply
  3. George says

    Good day Sir. Thank you for all your useful info. I know the answer for the 60 LED’s is already been answered. but I would like to know how to connect them all in the circuit. 4 lines x 15 LED’s per line in series or do I need to modify the circuit completely.
    Thanks for your feedback

    Reply
  4. Barclay Momin says

    I am looking for IC’s UTC 8156 and M668P. Shops I a looking can not help me. Can you help be. May be 3 pcs each for starting and trial. Thanking you.

    Reply
    • Swagatam says

      I am sorry, I have no idea from where this IC can be procured in the present time….

      Reply
  5. ARABINDA says

    Swagatam Sir, can i connect 60 leds to this circuit? if yes, please provide me a circuit diagram for this…my email is..(pintu.ericsson007@gmail.com) and whatsapp me at 8763364812

    Reply
    • Swagatam says

      Arabinda, you can use the last circuit for your requirement.
      make sure the upper line of the lamp is connected with the cathode of 1N4007 diode…and not with the mains line as given in the diagram.

      Reply
    • ARABINDA says

      sir, how to connect leds, 15 leds in each string or any other way ?

      Reply
    • Swagatam says

      arabinda, first buy the IC then I'll explain how to proceed.

      Reply
  6. Sandeep Badgujar says

    hello sir
    Where can I purchase the UTC 8156 and how much in india

    Reply
  7. Rakesh Maurya says

    Sir can i use BT136 in this circuit

    Reply
    • Swagatam says

      yes you can use it.

      Reply
  8. Rakesh Maurya says

    Sir आप कही बता सकते है ये ic कहाँ मिल सकता है ???

    Reply
    • Swagatam says

      Rakesh I have no idea about it, it's seems to be a Chinese part so it could be hard to find it in the local market.

      Reply
  9. Rakesh Maurya says

    Sir

    Is a problem, this IC (UTC8156) is not my area 🙁

    Reply
  10. Rakesh Maurya says

    हर channel पर एक

    Reply
    • Swagatam says

      connect the upper ends of the LEds to the positive line, that is at the line which connected with the cathode of the 1N4007 diode….and make sure to have a 10k resistor in series with each LED.

      no other variation is possible or recommended other than this.

      Reply
    • Swagatam says

      LED ke uper wale chhor ko diode 1N4007 ke cathode line ke saath jod do.

      har ek LED ke series me ek 10 k resistor hona jaroori hai.

      Reply
  11. Rakesh Maurya says

    https://lh3.googleusercontent.com/-RcmHojs6Jc0/VpdqJCMUe8I/AAAAAAAAAIc/ADhVtZ0ZUz8/w1060-h872-p-rw/PicsArt_1452448215971.jpg

    Reply
  12. Rakesh Maurya says

    हर Channel पर एक, जैसा की मैंने अपने image में show किया है

    Reply
  13. Rakesh Maurya says

    sir मैं आप से कुछ इस तरह से LED लगाने के लिये कह रहा था कोई तरीका हो तो please बताइए sir

    https://lh3.googleusercontent.com/-RcmHojs6Jc0/VpdqJCMUe8I/AAAAAAAAAIc/ADhVtZ0ZUz8/w1060-h872-p-rw/PicsArt_1452448215971.jpg

    Reply
    • Swagatam says

      how many LEDs do you want on each channel??

      Reply
  14. Rakesh Maurya says

    but sir i want use TRIAC with LED

    Reply
    • Swagatam says

      you can use scrs as shown in the first/second circuit, triac is not required for LEDs

      Reply
  15. Rakesh Maurya says

    क्या हम इस circuit को LED के साथ बना सकते है
    जैसा की आपके पहले वाले circuit में है

    https://homemade-circuits.com/2013/06/knight-rider-led-chaser-circuit-mains.html?m=1

    Reply
    • Swagatam says

      yes you can, remove the SCRs and directly connect 5mm LEDs between S1, S2, S3, S4 and the positive line

      Reply
  16. Rakesh Maurya says

    Thank you sir and i will try this circuit

    Reply
  17. Rakesh Maurya says

    but sir इसमें R2 और C1 की value क्या है

    Reply
    • Swagatam says

      same as in the original design, no change

      …..1M and 47uF/25V

      Reply
  18. Rakesh Maurya says

    लेकिन sir मुझे 200Watt/240V AC का बल्ब जलाना है
    जैसा की इस प्रोजेक्ट में आपने बताया है ऐसा कुछ इसमें बताइए

    https://homemade-circuits.com/2013/06/knight-rider-led-chaser-circuit-mains.html?m=1

    Reply
    • Swagatam says

      I have updated the diagram at the end of the article above…

      Reply


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