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HowTo: A low cost lighting sequencer (Pt 1)  (Roger Otis)


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Step 1 : Overview


This How To describes how to make a lighting sequencer out of inexpensive, readily available electronic components. The heart of it is a simple decade counter. Of course computer control is more flexible, especially if you have a huge display or want to sync with music or dim lighting. For those who are new to Christmas lighting control and want to get started without connecting their computer to some homemade electronics, this may be of interest to you. If you already have computer controlled lighting, it is a way to add some free running animation which doesn’t require programming or tie up more channels in your existing system. Or, maybe you don't have a computer to dedicate to lighting control. It is also particularly useful if you want to run multiple animated displays. I first saw the basic idea in a Popular Electronics or Radio Electronics magazine 15 to 20 years ago. The circuit controlled a simple jack-in-the-box display. By adding a few more components to the basic circuit I found it is much more capable than it would seem at first glance. It may not be a "Computer Christmas" but it can still be a "Digital Christmas".

Before you start ordering parts, please read the warnings in the Steps on SSR Control Boxes.

Step 2 : The Pulse Generator


The 555 timer IC generates pulses at a rate set by the 1 Megohm variable resistor or potentiometer. The LED from pin 3 to pin 4 visually indicates the pulse rate of the 555 timer.


Step 3 : The Decade Counter


CD4017 is a decade counter. As shown, the counter counts from 0 to 9 and resets to start the count again. Each pulse advances the counter with a corresponding “high” at outputs Q0 to Q9. I use optoisolator ICs to drive triacs. Only one output channel is shown. The optoisolator circuit is very similar to some of the other SSR circuits shown on this website.

In the most basic form, the transistor shown at output Q0 of the decade counter is really not needed. The decade counter can drive the LED in the optoisolator directly with the proper size of current limiting resistor. The 100K resistor, the 1K resistor and transistor can be replaced with a 1K resistor from pin 3 in series with the LED in MOC3010. The resistors and transistor are very useful for modifications which will be shown later and for the ability to add a display to check operation.

The 555 timer and CD4017 have wide operating voltage ranges. I use a plug-in wall adapter with a 9 volt DC output as a power supply. The voltage is unregulated. It is a good idea to place a 25 to 50 microfarad capacitor from V+ to ground. Neglecting the voltage drop across the transistor and LED in the optoisolator, the current through the LED is 9 volts/1000 ohms or about 9 MA.

Step 4 : The Circuit Boards


I use breadboards available from Radio Shack (276-174, about $15) for most of my circuiting. You can make printed circuits. Another option is to use the breadboard to check the circuit and then transfer the components to printed circuit boards which match the breadboards. These are also available from Radio Shack (276-170, about $3.50). Using breadboards tends to be messy because of all of the jumpers. The neatness depends on how much time you want to spend cutting and training wires. The output section with the transistors is the same circuit repeated for each output channel. Color coding of wire can help keep track of the wiring.

I apologize for the lack of detail in the photo. It is the best I can do for showing the whole assembly with the pixel restrictions for uploading. I know you cannot follow the circuiting. I have identified key components to give an idea of the layout.

The small lower breadboard is temporarily connected to LED bargraphs for checking the output of the decade counter. The outputs from the pins of the decade counter are connected to the LEDs in the bargraph in series with 1K resistors to ground. Since transistors are used to drive the LEDs in the optoisolators, the LED bargraphs can be left connected if desired.

For the project described later, we need two controllers which count to five. Each controller needs 5 outputs(Q0 through Q4). Both can probably be squeezed onto the same two breadboards. I have shown only one. To make the decade counter count to 5, a jumper is placed from pin 1(Q5) to pin 15(Reset) of IC CD4017. Be sure pin 15 is disconnected from ground. Pin 13 remains grounded. Note the outputs are labeled Q0 thru Q9. The count is Q0, Q1, Q2, Q3, Q4. The instant Q5 receives the count, the count is reset to Q0.

The middle breadboard contains the 555 pulse generator and the CD4017 decade counter. These are circuited according to the schematic diagram except for the jumper modifications mentioned above.

I use the upper breadboard as sort of a patch panel in addition to holding the output transistors. The outputs of the decade counter (Q0 thru Q4 are jumpered to the base of each transistor through a 100K resistor. Upper and lower rows of holes on the breadboards are the V+ and Ground connection points respectively. The collector of the transistor is connected to V+ through a 1K resistor. The points of connection for wiring to the optoisolators are from each transistor emmiter to ground.

I use flat modular telephone cables from the output transistors to the SSR boxes. The cable arrangement is described under the steps on SSR boxes. The cables enter my house through boxes on the outside of the house and pass through conduits over a workbench where the controllers are located. I solder short lengths of 24 gauge wire onto each of the wires in the cable and insulate the solder joint with heat shrink tubing. The short wires are compatible with the holes in the breadboard. It is important that the wires connected to the optoisolater LEDs never accidentally touch any of the V+ voltage on the breadboards or they will be burned out.

Step 5 : The SSR Box


Please note: Building SSR boxes is very serious business. They are for controlling 120 volt circuits. The following is not presented as a solution suitable for your particular lighting control situation. If you use it, it is at your own risk. It is your responsibility to meet your own local electrical safety codes and regulations. It is also your responsibility to size components, to construct units to prevent overheating and know how to safely handle electrical equipment.

I never place the SSR boxes inside or near buildings. I don’t put them in places readily accessible to people. The control boxes are plugged into outlets with GFCI protection. This will probably cause some nuisance tripping in wet weather.

The boxes are constructed of ˝” plywood. The length is sized for a cover plate for the power cord entry and fuseholder, 5 receptacles and a cover plate for modular jacks. The cord and plug has a ground and is polarized. The neutral is connected to the neutral side of all receptacles. The ground is connected to each receptacle. The hot strap between individual receptacles is removed. A wire is connected from the hot side of each receptacle to the proper terminal of the triacs.The data lines to the control boxes are flat modular telephone wiring. One is 4 conductor and one is 8 conductor. The 4 conductor cable is usually available at home improvement stores. The 8 conductor cable is available from www.jameco.com. You could use Cat 5 cable if you like. The flat cable is very easy to terminate into RJ45 & RJ11 plugs. The wire used to terminate the modular jacks to the optoisolators needs to be solid wire suitable for punching down on the jacks. I use Cat 5. I use one conductor from each cable as a ground for the common wire connected to the LED in the optoisolator. For the cable combination, this gives two grounds and 10 conductors (one for each ˝ receptacle. Do not connect the ground for the electronic circuits to the receptacle ground.

If you prefer, you can fabricate metal or plastic enclosures for the SSR boxes. I usually place the boxes in plastic garbage bags with the openings taped around the incoming cords and data lines.



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