Bypassing Multi Function Controllers

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Introduction

If you have a set of Christmas lights with a multi-function controller and you want the lights to just stay on, here's how to do it.

Most MF controllers are similar in concept and circuitry, but the circuit board layout can vary somewhat. Some are low voltage (24V - 36V) while other are 240V.

You will need to open the plastic case to gain access to the circuit board inside. Most of them are two halves glued together, so you'll probably need to carefully prise or saw it open.

Important: Make sure you do all of this work with the controller disconnected from the power source!

Additional considerations for lights purchased after 2014

Many larger stores (Bunnings, Kmart, Big W, and possible others) have changed their Christmas light manufacturing process for 2-channel twinkling/flashing lights, thereby reducing the amount of wires out of a multifunction-controller from 3 down to 2. The method for making these lights flash means every second LED is wired in reverse. When connected to a DC power source with a bypassed multifunction controller, only every second LED will turn on.

Want to know more about AC and DC power? Please refer to the Introduction > Definitions section of the AusChristmasLighting 101 manual.

Example 1

Join the two solder pads together in each of the red boxes. You can just put a large blob of solder over the pads. Make sure you melt into the original solder so the resulting joint is as one, not just tacked on top. This mod doesn't stop the controller chip from doing its thing (flashing) internally, but merely shorts out the electronic component (SCR or TRIAC) that does that actual voltage switching.

Controller bypass1.jpg Controller bypass1 top.jpg

Example 2

With this one, join the eight solder pads together in the red rectangle (towards the right). The easiest way is to lay a length of tinned wire across all the solder pads and melt fresh solder onto each one.

Controller bypass2.jpg Controller bypass2 top.jpg

Example 3

With this one, join the eight solder pads together in the red rectangle (towards the middle). The easiest way is to lay a length of tinned wire down the centre line of the solder pads and melt fresh solder onto each one.

Controller bypass3.jpg


A slightly different PCB design can be bypassed by joining the same eight solder pads. Controller bypass3alt.jpg

Example 4

"Light Up My Life" 240Vac multifunction controller. Join the eight solder pads together in the red rectangle.

Controller bypass4.jpg

Example 5 (Dick Smith)

"Dick Smith" low voltage multifunction controller. Join the eight solder pads together in the red rectangle.

Controller bypass5.jpg

Example 6 (Vicky Sun)

"Vicky Sun" low voltage multifunction controller. Join the four solder pads together in the red rectangle.

Controller bypass6.jpg

Example 7 (Vicky Sun)

"Vicky Sun" 240V AC flash controller. Join the two solder pads (arrowed in red) together.

Controller bypass7.jpg

Example 8 (Big W)

Big W controller for 160 LED set. (PCB marked DM-K1.1) Join the three solder pads together as shown by the red lines.

Important - This mod will make the set light up steady, but it appears that the supplied plugpack is a switch-mode type and dimming the mains input could see the release of the magic smoke!

Controller bypass8.png

Example 9

Controller for 100m LED rope light. (PCB marked D140) Join the four solder pads together as shown by the red line.

Controller bypass9.jpg

Example 10 (Uncle Bills)

Controller for Uncle Bills 20m LED rope light. (PCB marked PD-4F1-A) Join the two solder pads marked Q1 and two solder pads marked Q3 together as shown by the red lines.

Controller bypass10.jpg

Example 11 (YF-BS-3101)

Power supply / controller (marked YF-BS-3101).

You need to link in two places as marked by the red arrows. Once at the top-left of the image to do one channel and again near the middle-left for the other channel.

Take care not to short the wiring to the pin in the middle in each case. Clip the wires short or even better de-solder and remove the two small 3 pin transistors where the arrows are.

Do not do anything to the right side of the board (highlighted red) as this is at mains potential and is a shock hazard.

Controller bypass11 modified.jpg

Example 12 (Uncle Bills)

Controller for Uncle Bills 20m LED rope light. (PCB marked D-08A) Join the two solder pads marked 1 and two solder pads marked 2 together as shown by the red/black lines.

Controller bypass12.jpg

Finishing Up

Once the mod has been done, temporarily put the circuit board back into the plastic case and tape it shut. Test the lights set to make sure the controller has in fact been bypassed and you didn't let the magic smoke escape.

After you're happy that all is well, disconnect the power source again and seal the plastic controller box up permanently. If you prised it apart carefully, you may be able to simply re-glue it. Use some tape around the box to hold it while the glue sets.

Total MFC Removal

If you want to totally remove a multi function controller (water damaged, etc), you'll need to use 4 diodes (or a diode bridge) to perform the rectification that was occurring inside the MFC.

Controller bypass bridge.png

The low voltage AC (often 24V) from the transformer goes to the AC terminals (marked ~) of the diode bridge. It does not matter which way around they go.

A multi-channel LED string will one common wire and 2 or more channel wires. The common wire is almost always the one closest to the incoming power wires on the MFC. It is often marked with a piece of tape or by having a knot tied in it.

Connect the string's common wire to the + terminal of the diode bridge. Connect all of the channel wires to the - terminal of the diode bridge. Make sure you insulate all connections.

A diode bridge rated for 1 Amp and at least 50V should be all you need. They are usually part number W04 and can be bought at Jaycar or Altronics for less than a dollar.

W04.png Note that the two ~ terminals are actually diagonally opposite each other as are the + and - terminals (not on same sides as in the connection diagram above).

Important! Total removal of the MFC is only recommended for light sets that use a transformer.

Related

LED String Wiring

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