Here are special devices made for use with Christmas light strings.


There are at least 8 different electrical kinds of LED strings:

  • H1: A half-wave string that passes only one direction of the AC cycle.
  • H2: A dual half-wave string that passes one direction of the AC cycle through half of the string and the other direction of the AC cycle through the other half of the string.
  • F1: The string has a full-wave rectifier that sends both directions of the AC cycle through the same LEDS in the same direction. This is the most compatible LED string for special devices.
  • F2: The string has a full-wave rectifier with a filter capacitor that sends both directions of the AC cycle through the same LEDS in the same direction. This is the second most compatible LED string for special devices.
  • B1: The string has a bidirectional LED in each bulb. It passes current in both directions of the AC cycle through the LEDS.
  • D1: The string has a half-wave voltage doubler that uses both directions of the AC cycle to double the voltage through the LEDS. This requires a full-wave AC power source.
  • S1: The string has a switching power supply to power the LEDs (It does not flicker. But most special devices cannot power it).
  • C1: The string has its own special controller that could have any kind of power supply. But it has its own controlling functions that make the lights do things.

Note that any of these different kinds can have several series sets of LEDS in parallel (as seen in the F1 and F2 diagrams) or just a single series (as seen in H1). The number of sets in parallel does not change the kind of circuit.

Kinds of strings of LED Christmas lights:

the strings


I titled this because the name fits the display I made using this circuit. Actually, it makes a string of miniature incandescent or LED Christmas lights blink on and off with reduced brightness. This uses a twinkle bulb to blink the lights. Adjust the wattages of the two small bulbs so the twinkle bulb blinks and the LED string lights.

This works with the H1, H2, F1, F2, B1, and D1 types. It probably won't work with a sophisticated power supply such as S1 or C1.

I used another string of lights (Westinghouse Holiday Spectacle of Lights) to provide a constantly varying colored background behind the blinking pattern of white lights in the foreground. I tried to photograph the effect, but it isn't visible in the photo the way it is when actually seen.

This can be used for a variety of blinking effects. Use your imagination.



star-cross This circuit uses the two halves of a H2 dual half-wave string or two H1 half-wave strings to produce two flashing effects in the same pattern. It can also be used to make two sets of straight-line H1 lights intertwined together produce an interesting flashing effect.

In the Star-Cross pattern shown, one of the half-wave series lights the vertical and horizontal arms of the cross. The other half-wave series lights the diagonal rays and the lights at the tips and center of the pattern. This produces a pleasing twinkling star effect.

Each of the half-wave series can be off, half bright, or fully bright, giving 9 different instantaneous displays. This can also be used with the F1, F2, B1, and D1 strings to light a single string with 6 different shimmer brightness levels (including off). It can also supply both H strings and F strings to produce an even more interesting combination of blinking and shimmering.


star-cross This circuit was formerly used to light the same pattern (above), and later, an F1 full-wave string in the shape of a 5-pointed star with snowflake patterns around it. It provides a shimmering effect with the Star-Cross string, or causes the Start-Flake to shimmer to 3 different brightness levels.



bell Sequencers are fun. They can be used to animate any display. The swinging bell display shown here uses a 1|2|3|2| oscillating pattern (Osc 3 below) that sequences three different images to produce the effect.

Sequencers have three different kinds of components:

  1. A clock (usually with variable speed)
  2. A Counter operated by the clock (this one has individual outputs for each count)
  3. Lamp decoder drivers

Many sequences are possible. Only the counter and the number of decoder drivers limits your choices. Here are some useful sample sequences, with sample displays, shown in the order seen in the diagram on the right:

Rotate 3

  _ _ _ _ _ _ _ _ 

Osc 3

  _ _ _ _ _ _ _ _ 

Rotate 4

  _ _ _ _ _ _ _ _ 

Osc 4

  _ _ _ _ _ _ _ _ 

Walk 3

  _ _ _ _ _ _ _ _ 

Colors 3

  _ _ _ _ _ _ _ _ 

Spin 4

  _ _ _ _ _ _ _ _ 

Walk 4

  _ _ _ _ _ _ _ _ 

tree The colors shown are based on the lamp drivers having these colors plugged in the drivers:

1=red, 2=green, 3=blue, 4=white

Use your imagination to devise different kinds of displays to use these sequencer patterns. They can be chase lights running around a room, animated cartoons doing various things (e.g. the bell above), rotating stars (as in the examples), color changing effects (as in the examples - using different colored strings), lighting the tree panel at right, or even simulating one of those 1960s color wheels (using 3 or 4 different colored floodlights).


The diodes are small signal diodes with PRV larger than 15 V. They let any number of counter outputs work a single lamp driver. The 9 V supply is a 9 V battery replacement wall transformer. Choose the triacs to match the load you have.

Switches can be interposed between the diodes and the 24 K resistors to make the same lamp drivers use different sequences.

Since line voltages are present, build all of these to National Electrical Code requirements.


Fun with Christmas Lights

Christmas Light Tester for Special Device use

Light Bulbs, Spectra, and Vision