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Audio activated switch/lightning machine�CHEAP!

23813 Views 22 Replies 10 Participants Last post by  djjerme
Audio activated switch/lightning machine…CHEAP!

I spent quite a while looking for a switch that would activate whenever it got an audio input. I found several that used one of those cheap microphone inputs, but nothing that took a line level input. You really need a line level input so you can send the output from a CD player, the output from an audio mixer, Tape Deck, computer sound card or just about any other source.

You don’t want other random sounds setting off your prop like the sounds from other props, or noises made by TOTers. You can use this method to set off props or synchronize lightning to thunder sounds. Even have the lightning first followed by the thunder a second later. (That’s what I do) You can use this to control any size prop with any power requirement. I’ll show you how.
The first thing you need is an LED VU meter kit. If you buy a stereo version, it will give you 2 controllers. For this illustration, I will show the mono version. This will make 1 controller.

I built several and mounted them all in one project box from Radio Shack which gives me control over 6 separate props in one box.
Let’s get started. Buy the kits you need. The mono kit looks like this:

Technology Audio equipment Electronic device Electronic component

It is kit #CK-104 http://www.canakit.com/5-led-vu-meter-kit-ck104-uk104.html from Canakit.

Converting this kit is REALLY simple. Build the kit according to the instructions except where it comes to the LEDs. Here’s the part I can’t remember, and the ones I built are all packed away at the moment. I forget which end is the Low volume end and which is the high volume end. Meaning which LED lights up first with the lowest volume level and it goes up from there. From memory I believe it goes from right to left, but I may have it backwards. The easiest way to tell is to put long wires where the LEDs normally would go at each end. Making sure to keep the polarity right, hook an LED to each set of wires and run the kit by putting an audio source to it. The LED at the low end will light first with the quietest sound, and the one at the high end may not light at all unless you are really blasting the input. Then you will know which is which. I also actually do hook up the second relay in the series just so I have visual indicator that shows me when the switch is ON. I mount the second LED on the outside of the project case where I can see it. You don’t need to do this part, but I like to have that visual cue.

Once you have done that, cut off the wires at the high end leaving the long leads at the low end in place. The wires at the low end are going to connect to the control wires of a solid state relay that looks something like this:

Product Technology Electronic device Electronics Electronic component

Again, be sure to observe the polarity and hook the two leads that would normally have gone to the first LED in the array to the control leads on this solid state relay. (The bottom two leads on the Relay). I use this particular brand, but there are many variations to it. You can choose to buy solid state relays that can switch up to 10 amps or more or as little as 2 or 5 amps depending on your application. You can find these all the time on eBay. Just type in “Crydom solid state relay”. The ones I use will switch on when the control voltage is between 3 to 30 VDC. The one pictured takes 3.5 to 15 VDC, but that would be fine as well. I forget the exact output voltage that goes to the LEDs, but it is in the range needed to run these Solid State Relays. Here are the Specs for a Crydom Solid State Relay that will work. You can of course use other brands with similar specs if you wish. Just find the best deal.

You will need a power supply to run the VU meter Kit. I used a 9VDC supply and it was fine. It can use a voltage range from 4 – 14 VDC at 100mA. If you are going to run 2 kits from the same power supply, make sure it is at least 200mA. 3 kits/300mA and so on.

The solid State Relay (As far as I can tell) Only Switches AC voltage. If you want to turn on or off a DC powered prop or speaker wires to turn on or off a sound or strobe light control wires (like I do) to control a lightning effect, then simply buy a standard Relay with a 120VAC coil similar to these on eBay HERE. Let the solid state relay turn on and off the standard relay, and use those contacts as a switch for whatever you want to control. For DC powered props, you can use a wall wart power supply that plugs into 120 VAC and provides you with the proper DC voltage and switch the power that goes into that wall wart on or off with the solid state relay.

Now for the part where I control the props and synchronize lightning and so on. You can split the output from your CD player or other source and feed half of it into this kit and the other half to the amplifier or amplified speaker. That would work….BUT…here’s the problem:

If you want a prop to be activated or lit up or to do whatever you want it to do continuously while you play your sound effect, you may not get that result by simply playing your sound into this audio switch. If your sound changes in volume or has quiet parts in it, the switch will go off when the volume level drops below a certain point. In some cases, that may be the effect you want, but in others, you may want the prop to be activated the whole time that the sound is playing or maybe even longer.

Here’s how I handle that. I use audio editing software to create my audio files. I use Sound Forge and Adobe Audition, But Audacity should work fine for you, and it’s free. I create a stereo sound file . Actually, I should say 2 track because the exact same sound is on both the left and right channel. Dual Mono is probably more accurate.

If you want to have your prop react exactly to the variations is the audio file you create, simply send one channel to the VU meter kit that you modified, and the other channel to your amp and speakers.

If you want the prop to turn on for a pre-determined length of time no matter what your audio file does, then you need to create a special audio file. I use a constant audio tone that you can download HERE.

(You may have to right click on that link and all other sound links and choose "save target as' to download it)

I have that run in one channel for as long as I want the audio sensitive switch to keep the prop on. The other channel is the sound that I am sending to the amp and speakers. You can download an example of the file I made HERE. That file is one I use for a banging coffin. I have a motor inside a full sized coffin that is half buried in the ground. There is a red light and a speaker inside that coffin. I want the sound to play, and the motor and light to be activated the whole time, banging the lid slightly up and down while the red light is on. I want the light and motor to stop just before all the sound trails away. As you can see in the audio file I created, the tone starts just after the initial sound, then stays constant until it shuts off a few seconds before the last sounds trail off. Since the volume level of the sound effect I made goes up and down a lot, the switch would have turned on and off several times which was not the effect I was looking for there. Using different audio on the two tracks solves that problem completely.

To create the effect of lightning flashing before the thunder I create another special audio file for each different thunder crash sound effect I have. You can download one of these files HERE to see how I did it. Another way to do this without using the 'tone' method would be to shift one of the channels of audio a second ahead of the other. Send the channel that plays first to the switch, and the duplicate channel that is slightly delayed to the amp and speakers. Then your spotlights and/or strobes would flash in the same pattern as the sound, but would happen a second before you hear the sound. If you were to play a track like this in headphones, it would sound like an echo, hearing the sound first in one ear, and then a second later in the other ear. You can download an example of this audio file HERE.

Again using tones, I decide when I want to activate the prop, in this case the audio sensitive switch is controlling a relay that switches on 4 large 1000 watt strobe lights which I use for lightning. The other channel of the audio file goes to my 950 watt amplifier and speaker which is in a second story window in my house. I start the tones about a second before the sound effect starts and use several short bursts to simulate real lightning, rather than just having the strobes on constantly. This will work just as well if you are using bright spotlights for your lightning instead of strobes. You can control the spotlights directly from your solid state relay without having to use a secondary relay.

Anyway, I hope I have explained this all well enough. If you have any questions, don’t hesitate to ask them here.
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Sorry about the ebay listing.

Those links tend to go away after a while.

Just search the web for relays with 120VAC coils and you will come up with things like this:

Hopefully this link will stay active for a while. This relay can handle 12 Amps through it's contacts. Since it is a double pole, double throw (DPDT) relay, you can split the power through two sets of contacts essentially doubling your current capacity to 24 amps.

Alternately, you can just keep searching the web for relays that can handle more current through their contacts.

12 amps should be plenty for most applications, although I have a motor that draws more than that when it kicks on. Not continuously, but when it starts.
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I don't think they would.

I believe you have to have an AC voltage for the coil. The contacts are fine, though.

The reason is that the Solid State Relays switch AC voltage on or off. I don't think they can switch a DC source. If someone knows facts to the contrary, please post, but my experience is that a solid state relay like the ones I used that get turned on and off by the LED signal can only switch an AC load, therefore, the coils on the relays must be AC.
I recommend having the solid state relay operate a heavy duty 120 VAC standard relay for heavy loads. That way, you don't need a heat sink on the SSR, and you can switch anything you want depending on the size of the standard relay you choose.
This circuit isn't really designed to control jaw movement on a skull, but I understand the frequency and filters bit. I would use that idea for simple on/off switching. Sounds like you need servos and servo controllers here.

If all you need is to turn on or off a motor or a switch, and you want to control muliple on/off cycles from one audio file, you can easily do that with tone switching. Here's how I would set it up. One channel of the stereo audio would contain the straight audio that eveyone would hear.

The other channel would contain the different tones. The VU meter switches I talk about in this post would all have their inputs hooked to the output of the 'Tone" channel, but that output would go into a filter first.

Something similar to a low-pass filter that blocks everything except bass frequencies would be used, except you would want more precise control over what frequency range would be allowed through. There are circuits and schematics available online for this sort of thing. It is how electronic crossovers in stereo equipment work.

Here is my example:

you have 4 switches you want to control at different points within an audio file.

Use 4 different tones created by a tone generator. All at different frequencies. One could be 100 hz another could be 500 hz, a third 1000hz and 1500hz could be the fourth.

You would need 4 filters. Their job would be to block everything except the frequency range they are set up for.

In this example, one filter would be designed to block every frequency above 150hz. This would allow the 100 hz frequency through, but block all others. The output of your "Tone" channel would feed into that filter, and the output of that filter would feed into the audio switch you made from the VU meter. The only thing that would activate that particular switch would be frequecies below 150 hz. Therefore, if a different tone were to overlap, let's say that they 500 hz frequency also hits while the 100 hz frequency is playing....Only the 100 hz frequency would get through the filter to this particular switch and it would not "hear" any other frequencies, therefore would not react to them.

The 500 hz tone would be there, but would be blocked by that switch.

Also hooked up to the output of the "Tones" channel would be three other filters. One of them would be set to block all frequencies except those within the 400 to 600 hz range.

This second filter would feed the input of a second audio switch made from the VU meter.

That second switch would only "hear" the 500 hz tone because all other frequencies would be blocked. It would only turn on for the 500 frequency whether any other frequencies were present or not.

You would do the same for the other two filters. Each of them set to block everything except the one frequency that you want to allow through.

This would give you the on/off control for as many switches as you want, all fed from the same audio channel with as much overlap as you want.

You could even take it a step further and mix the tones right into the existing audio track. Just choose frequencies that are above or below the ability of the human ear to hear. If the filters are set up to allow those frequencies through, they should still register on the VU meter and control your switch. You might drive some neighborhood dogs crazy in the process, but it should work.
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I will attempt to answer all your questions by addressing them as you posted them:

[{"The VU meter switches I talk about in this post would all have their inputs hooked to the output of the 'Tone" channel,"}]
~I didn't see a line-in or a lineout on that VU meter???
is the line out the LED's?? Just checking

Yes, the output IS the LEDs. I no longer think that you need to use the VU meter at all. I was telling you that the VU meter will work to turn things ON or OFF. It will NOT give you an audio output that will drive your skeletons the way you want. For you, the process I outlined above will still work, but you will not need the VU meter switches, so you save money.

You tell me that your skeletons accept an audio input which controls when the mouth opens or closes. I didn't know that before. So now all you have to do is to send a different audio signal to each skeleton (by the use of filters) and it should work. You can adjust how long the mouth stays open by adjusting the length of each tone that you send.

Sorry if the questions seem stupid, but this will be my first time.

There are no stupid questions........ok, well very few. This isn't one.

So what or where do I pick up an audio filter that I know will filter out the right tone to the VU meter switch?

You don't pick them up....you make them, and as stated above, you won't need the VU switches.

Are they cheap?

Yes. Just a few electronic components that you have to put together.

Also with two channels (left/verbiage- right/tones) do I just Y (4 lines) divide the right channel to each of the four skeleton heads?

Yes, that is how you would do it. You just need to be sure that after splitting the signal 4 ways, you still have enough signal strength (Volume) to trigger the skeletons. If not, they sell pre-amp kits that you can build to boost the signal. (here is one. http://www.hobbytron.com/vk2572.html It is stereo, so you only need to use one channel. I know they sell mono ones that are cheaper. You would boost the output before splitting it and sending it to the filters)

So I am correct in my assumption, let me text out your design and see where I need corrections or not.

Four Skellys talking:
1) MP3 Player with stereo track (left/verbiage- right/tones)


2) left channel is output to the amp


3) Right Channel is y'd out to the four skeleton heads


~Each head has the following setup:
a) Tone line output to Filter


b) Filter output to VU meter switch

Again, skip the VU meter switch and go directly to the skelly's from the filter output.

c) VU meter switch output to Skelly head (for on off action)

Also I was wondering if i use a Stereo VU would I optimize my circuit usage? (by two instead of four)

It would if you needed them.

And now.... Let's get back to the filters. Here is a good webpage that explains what a band pass filter does. http://www.allaboutcircuits.com/vol_2/chpt_8/4.html

yopu would need 4 of these circuits. They would all be the same except for some of the component values. It is a combination of a low-pass filter and a high-pass filter. The high pass filter passes (or allows through all frequecies ABOVE a predetermined level. Then the low pass filter passes all frequencies BELOW a predetermined level.

So if the high pass filter is set to block everything below 400hz, then only those frequencies ABOVE 400 Hz would get through. That output is then sent to the Low Pass filter. We would set the low pass filter to block everything above 600 Hz which means that it would allow everything which is at 600 Hz or LOWER to get through.

Since it was not fed anything below 400 Hz, the only thing that would get through would be frequencies between 400 and 600 Hz. This would be a good filter to use for your 500 Hz singnal Pulse. That would operate one of the skeletons. Even if 3 other frequencies were present at the same time, they would have all been blocked by this filter and only the 500 Hz frequency would get through.

I will look for more schematics for building the band pass filters and post some when I find them.
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Go to this site and about halfway down, under Calculating Frequencies, download the program they offer. http://sound.westhost.com/project63.htm

In the Calculate R column, enter the frequency you want to allow through, then enter 1 for Gain, and 10 for Q. That will provide you with the values for the components in the schematic.

Repeat this using all four of your desired frequencies, then run off to Radio Shack to buy parts.
w0w. You are intensely weird. very c00l
You are very observant. Unfortunately, I think some of the links in this thread are now just as dead as Radio Shack, but the concept is still valid.
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