Introduction: Audio-Controlled Christmas Light Flasher With Individually Controlled Stereo Channels

Picture of Audio-Controlled Christmas Light Flasher With Individually Controlled Stereo Channels

In this Instructable, I will show you how to control things powered by 110V AC with an audio signal. This project was inspired by a similar one done by Alan Parekh on a different site, originally created by rybitski at, but I have made some revisions (not all on purpose) and the instructions here will be much more inclusive.

Please be careful. Unplug first when working on anything electrical. 110V AC can kill you!

Step 1: Acquire Parts

Picture of Acquire Parts

In my design, I decided to retain stereo capability. In order to do this, I had to double the required parts. Here is a list of parts required:

--Pair of amplified computer speakers. A medium-to-large case would make things easier. Also, a standard, integrated power cord (non-wall-wart transformer) can free up a lot of space inside. I used a used set of Gateway Edison 2.0 speakers I bought from a used computer store for $5.
--An outlet, which I bought at a local hardware store for $0.59. You can decide if a cover is required for your application.
--2 Rectifiers. I bought mine from RadioShack. I decided to buy the 4A, 400V-capable units, to be on the safe side. They cost about $2.50/apiece.
--2 Solid State Relays. I followed Alan Parekh's example and used 2 Crydom D2W203F relays. I bought these from Mouser for $8.80/apiece. These are by no means the only units that can be used, but they work great.
--2 Potentiometers, to match the original that will be replaced. Mine was a 10k. These cost me $3/apiece at RadioShack.
--2 knobs to fit on the potentiometers. These cost me $3/pair at RadioShack.
--If your speakers have a wall-wart transformer, you will need a power cord to get the 110V AC inside the speaker cases. You can buy these from RadioShack, hardware stores, or simply cut one off of an old appliance you are no longer using. Again, please use caution and unplug anything before working on it.

Tools Required:
-Soldering Iron
-Wire Strippers
-Electrical Tape
-Small-gauge wire (I used 22ga stranded)
-AC-rated wire (or just cut a bit off your power cord, like I did)
-Some others may be required. I also used scissors, a cordless drill, side- and end-cutting pliers.

Step 2: Take Apart the Speakers

Picture of Take Apart the Speakers

My speakers had a press-on grill that could simply be pried away. I then removed the screws which retained the speaker. After this was open, I used my soldering iron to remove the speaker entirely.

Then, I carefully opened up the case on the computer speaker that contains the amplifier. I practiced on the other speaker first, in case I destroyed it accidentally. Unfortunately, the speakers that I was using were glued together, which made them difficult to pry them apart without breaking.

As I was taking the speakers apart, I forgot to take off the volume control knob and remove the nut underneath that held the potentiometer in place. This broke the potentiometer, which turned out to be a blessing, as I will show later.

Step 3: Position the Outlet

Picture of Position the Outlet

Next, figure out where you are going to place the outlet in the speaker casing. I found that the place where the speaker had been located was perfect, requiring only a little modification. Using a knife (be careful), I cut out holes for where the outlet was to be located on the speaker grill. If you have access to one, a Dremel tool would be perfect for this job.

Step 4: Wire Up Your Rectifier/relay Array

Picture of Wire Up Your Rectifier/relay Array

In order to package the rectifiers and the arrays in the case of the computer speakers, I decided to use a small scrap of plastic to hold everything in place. This can easily be done with some thin plastic and a cordless drill with a small bit.

The purpose of the rectifiers is to take the alternating signal from the speaker outputs and convert it into a DC signal. This signal can be used to control 110V AC through the relay.

Solder the speaker output wires to the AC (or ~) leads of the rectifier. Then, using short wires, connect the + lead of the rectifier to the + lead of the relay. Connect the - lead of the rectifier to the - lead of the relay.

Cut the wire attaching the other speaker and strip the ends back. These will be your AC leads for the second rectifier. Repeat the process, referring to my pictures. Wrap all leads in electrical tape to prevent short-circuits.

We will leave the arrays as-is for now and focus on replacing the potentiometer next. This will make things easier, as connecting the AC severely limits working space.

Step 5: Replace the Potentiometer

Picture of Replace the Potentiometer

Since I had broken the dual 10k potentiometer w/switch that was originally included with the speakers, I was forced to replace it. My local RadioShack did not have any one part that would directly replace it, so I bought 2-10k audio potentiometers and used a switch I had left over from a computer power supply that I had cannibalized. These potentiometers (aka variable resistors) cost me $3/apiece.

The next thing to do is solder short wires to the holes where the leads of the old potentiometer used to be. This should take 8 wires.

Next, you should make any necessary modifications to the faceplate. I drilled two large holes and two small locating holes for the potentiometers, as well as cut out a hole for the new power switch.

Test fit the potentiometers, and cut the shaft to length using a small saw.

Now, making sure to keep the same orientation, solder the other ends of the wires to the new potentiometers.

Then, solder the two wires left over to the switch. You may have to put the switch wires through the switch's hole before soldering. Wrap the leads in electrical tape to prevent shorts.

After this, I plugged in the wall-wart transformer and powered up the circuit to test. The LED power indicator lit, so I plugged in a pair of headphones and listened for changes in sound when I turned the potentiometers. This is how I figured out which Potentiometer controlled left and which controlled right sound channels.

Step 6: Wire Up the AC and Relays

Picture of Wire Up the AC and Relays

Now, after running the power cord through the back of the speaker case, wire up the wall-wart and the outlet in parallel, with the relays as switches. (If you need help, refer to the drawing.)

Solder the power cord and the additional wire stubs to the wall-wart transformer's plugs. You will need one short wire to go to the outlet, as seen in white, while the other side must go to both relays. I used a single wire and stripped some of the insulation from the middle and end of it to suit this purpose.

Now you are ready to solder your relays on. Connect the + to the Rectifier's positive and the - to the Rectifier's negative. Then solder the black wire from the power cord to one AC lead on each of the Relays. Then solder two short wires from the other AC lead on the Relays to each of the outlets, where the tab had been broken previously. Wrap all connections with electrical tape.

Here I will break down all the electrical connections required.
Right Speaker to AC legs of Rectifier R
Left Speaker to AC legs of Rectifier L
+ Rectifier R to + Relay R
- Rectifier R to - Relay R
+ Rectifier L to + Relay L
- Rectifier L to - Relay L
Power: 1 to Wall-wart, outlet side A
1 to Wall-wart, Relay L AC1, Relay R AC1
Relay L AC2 to Bottom outlet side B
Relay R AC2 to Top outlet side B

Step 7: Fit Everything Into the Case

Picture of Fit Everything Into the Case

This last step is easy--you've already done all the work! Just put everything into the case. I found it was easier to remove the speaker grill-outlet assembly and use the hole to push everything into place. I decided to use electrical tape to put the case back together, just in case I needed to take it apart again. After the case is back together with the speaker grill in place, attach the knobs.

Also, don't forget to run the wall-wart transformer's DC power to the circuit board. In my case this meant wrapping up the excess cord and running a short bit of it out the bass port in the back of the speaker housing to the original location of the power plug.

Step 8: Enjoy

Plug it in and try it out. Use the individual volume controls to adjust the thresholds on each channel independently. Play your favorite Christmas (or other) music and watch it flicker to the music.


CobraTester (author)2013-12-21

I like the design, I'm trying to figure out a way to do the same type of thing but also split frequencies to different bits of light-strings.

Such that the low end and treble send electricity to different channels. But alas, I cannot remember the EE from 20 years ago well enough to recreate the system I had in college.

I was thinking a low pass and a high pass filter added in before the rectifiers. (This would of course mean doubling everything down the line (4 rectifiers, 4 relays, 2 double outlets)

Any ideas on parts (or advice that I'm way off base)? I don't want to burn my house down or electrocute myself.

devicemodder (author)CobraTester2016-12-13

lm3914 maybe?

gilman49robert (author)2015-11-16

Hi just wondering what voltage you are getting off the left and right out put for the speakers

The Saints (author)2015-04-05

Does anyone know where I can find a relay switch that could just be laying around just about any home

The Saints (author)2015-04-05

Does anyone know where I can find a relay switch that could be laying around just about any home

bocaj812 (author)2009-04-04

I Dont Know If You Have Seen Ap Digital Lights Instructable For The Laser Light Show, But I Am Making Something Similar But Using An Arduino. I've Been Searchign On THe Web For Wuite Soome Time On A Way To Convert Low Frequency Sounds Into Low Voltage Eletrical Pulses To Feed Into The Arduino. I Saw this Instructable And Wandered If Anyone New If I Could Use This Basic Principle But Feed The Mono Channel Through A Low Pass Filter And Connect It TO The Rectifier Then To The Relay With A 5 Volt Connection Out Of The Relay To The Arduino. And Do I Have To Include The Speaker Amp Or Can I just Feed Audio Directly To The Rectifier?

Deathstick (author)bocaj8122010-12-08

Boy it is amazing how hard it is to read a sentence where every word begins with a capital letter!

josheee12 (author)2010-08-07

A quick question. I hate soldering. Would it be possible to use a CCFL sound module, and take the output (PWM) and smooth with a cap, and put the relay at that point?

rybitski (author)2010-07-11

I enjoy your modifications to my original project I just have one correction. Although my how-to was reposted on I am the creator. I can see where you may have been confused: "Written by: Alan Parekh..." Please double check and you will find that he is linking back to my old site. Thank you.

Ram15004x4 (author)2009-10-22

Great instructable. I just have one question.

Do you know how many watts each outlet can handle?

planelover93 (author)2009-07-03

Can you connect a multiple outlet strip to each channel to connect more lights?

DIY Dave (author)planelover932009-08-24

Yes, you could as long as they (the lights) don't use to much power.

planelover93 (author)2009-06-20

What is the Output Amps and Voltage on Each of your Channels? Please check your inbox, ive sent you a PM.

mooch91 (author)2008-12-04

I'm confused what is a relay? I'm making one but I stuck on step one still can you help me please

fallenspirit123 (author)mooch912009-02-23

A relay is basically a switch, it turns either on or off depending if you but electricty in it or not- I simplified it right there and believe me it is really simple, I struggled to understand what it is and now I understand it and love it! heres a link to help you

MustangChris429 (author)mooch912008-12-05

A relay uses low-current DC voltage to operate a magnetic coil. That coil opens or closes a switch on a high(er)-current circuit. This is handy for controlling high-output devices with low voltages such as an audio signal or a computer output. Wikipedia explains it pretty well.

Killa-X (author)MustangChris4292008-12-05

Would a SCR actually work better? They are the same thing as a relay just not mechanical. You use a battery for sample to trigger it, and that opens a gate for the source power...I know the switching speed is WAY faster than a relay, but I don't know if thats a concept in this project...

MustangChris429 (author)Killa-X2008-12-06

It may be good, I don't know much about it. I do know that what I used here was a solid-state relay, which does without the physical coil I do believe. I have no idea how they work, but I know they're different.

flash1322 (author)2008-12-05

that room looks exactly as the room on the hallmark commercial

Haha, that was my dorm room :)

the one in commercial

No, this video. I haven't seen the commercial

puffyfluff (author)2008-12-05

This is awesome! I'll make one in the next few days.

firehazrd (author)2008-11-22

great idea! I'm always looking for "cool flashy light thingie" ideas! can't wait to build one.

sdallesasse (author)2008-08-16

So, if you wanted to control lights using for instance a 5.1 surround receiver, you could set up 3 duplex recepticals (1/2 for each speaker / signal) in a similar maner to the one that you have here.

Coffee bean (author)sdallesasse2008-11-11

YES u cut back light your speakers and tv with LEDS! great idea

Coffee bean (author)2008-11-07

will adding more of these relays and rectifier allow for more channels

Coffee bean (author)Coffee bean2008-11-11

nevermind took a second look at it

icalbert101 (author)2008-11-10

Ok I'm in the middle of this build and I ran into a problem. I decided to use a 2.1 system mostly because i had an extra one. now the sub will put out enough juice for the relay used in this build BUT the satellites only put out around a volt. and for the life of me i can't find a relay that will work. i ordered two from mouser thinking i had it but didn't read the fine print or something and they are the size of a lady bug( i think they'll fry) any help?

Yerboogieman (author)2008-11-10

my dad saw Trans Siberian Orchestra on saturday.

qwertyboy (author)2008-08-08

hey! i have this song! Trans-Siberian Orchestra rocks!. cool instructable

Jakeg (author)qwertyboy2008-08-29

i went to see them live it was so awesomely cool

qwertyboy (author)Jakeg2008-08-29

i've seen them live too!

benthekahn (author)2008-07-20

I had the exact same Idea but you beat me to it!

muzac (author)2008-07-19

I'm still getting the hang of the electronic stuff, but you happened to have some kind of mixer with different equalizer settings set to different output channels, AND you made multiple Light Flashers, I would think you could pretty much direct different sounds (or instruments) in recordings to different light strands. Elaborate, sure, but a thought for a major project to awe the neighbors!

omnibot (author)2007-12-13

Very cool and inventive use of a computer-speaker, those things tend to lay around. I'm a bit criticall about the soldering on the transformer, every book I've ever read told me not to solder highvoltage AC, apparantly there's danger if you get a bouble of cleaner (don't know the english word, the brown stuff in solder that cleans the contacts) wich could explode or otherwise cause the soldered connection to fail.

MustangChris429 (author)omnibot2007-12-13

I believe you're referring to rosin, and I've never heard of that, but I'm not an electrician. I'll keep that in mind and let everyone know if I ever experience any trouble.

sandpaper first, if you put on too much rosin u can wipe if off gently with a cloth and it usually leaves enough on there to still work. if you are using a rosincore solder then u might not even need it use a lot of solder and you should be ok -getto style

Megatronic (author)2008-05-28

Hi, Frequent reader of Instructables . I have some suggestion that proven work and safe to use instead of bulky transformer and relays that overheat when you are not around and causes fire, use a single triac 110/220 VAC the gate is connected to a resistor for current limit and connect your output device with signal diode IN4148 to gate of your triac .

alleyezonme (author)2008-02-22

I actually tried this and it worked!!! The only problem I had was fitting the whole thing together. I made a small modification to this... I made this with outdoor parts and epoxy for the parts that were not outdoor. it looked so cool when you watched it...

Awesome! Glad to see I inspired someone else to try it out!

Nirjuana (author)2007-12-15

Very nice idea, but I'm not so sure about the relays, they usually have limited switching time and this can burn out them quite fast since they usually have lifespan measured in switch-times, but I'm not sure because I don't know so much about solid-states. Wizards in the winter and Christmas lights :P

tm36usa (author)2007-12-13

Nice Instructable. I just finished off a variation of this today as my EE final project. Used Optocouplers and triacs though. I decided the optocoupler so the 120v AC circuit and the ~1.5v DC circuit never came in contact as to not risk injury with a short. Also how fast is the reaction time using relays? I would think there might be some delay considering its mechanically switching with the electromagnet. Great work and innovative case idea.

MustangChris429 (author)tm36usa2007-12-14

The relays I used are Solid State and do not use magnets or mechanical movements. Exactly how they work, I do not know. According to the datasheet, max turn-on and max turn-off are "1/2 cycle," which I would assume to be 1/120th of a second, since the wall power (the only thing the relay experiences in cycles) is at 60Hz. This would mean 0.0083 seconds.

scolberg (author)2007-12-13

Very Cool Build! It should make a good lightning machine for halloween too. Can you provide part numbers on the rectifiers?

MustangChris429 (author)scolberg2007-12-13

I'm not sure, but I think I used these from RadioShack: 4A, 400V Full-Wave Bridge Rectifiers Model: 276-1173 | Catalog #: 276-1173 Rated 4-amps, 400 Peak Inverse Voltage (PIV). Really, you could use just about any you wanted, as long as they are rated for as much amperage as the Relays.

GorillazMiko (author)2007-12-13

cool! good instructable especially with the holidays coming up!

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