[GOT]

I basically want a lamp (can be AC or DC) to dim in response to the volume of a recorded sound. That is, the light is on normally, but dims when a recorded sound is played. I am not looking for a on/off system with some threashold volume. I need it to dim slightly to soft noise and more to louder noises. Can anyone help?

 

[Dr Morbius]

why would you need this?

 

[MansionHaunter]

Depending upon the lamp you use (and the power supply it requires), the circuit can be either very simple or somewhat complex.

How bright does the light have to be, and what is it illuminating?

 

[GOT]

I want the lights to dim when my ghosts pass screaming through the room. The light does not have to be bright. A flashlight bulb would suffice.

 

[jrzmac]

i think this is what you're talking about: http://www.hauntmasterproducts.com/14.html . i want to do the same thing, but 70. is a bit steep for me.

 

[Stratusfear02]

Very cool concept. From watching any show on paranormal activity we know that "they" draw energy to manifest. therefore the dimming/flickerng of lights is one neat idea. I'll have to do some research on this one

 

[jrzmac]

basically i want the lights indide the house to flicker, when the flood lights flash outside from the tnl machine. sound simple enough, but.... i tried hooking up the tnl machine to a flip flop control thing i built, it actually worked, as the lights would stay lit and flicker off when the thunder sounded, but the damn relay was buzzing like a son of a b...

 

[gmacted]

basically i want the lights indide the house to flicker, when the flood lights flash outside from the tnl machine. sound simple enough, but.... i tried hooking up the tnl machine to a flip flop control thing i built, it actually worked, as the lights would stay lit and flicker off when the thunder sounded, but the damn relay was buzzing like a son of a b...

I wouldn't use a relay in this application unless it was a "solid state" relay. Most relays are mechanical in nature and will "wear out" with use. Data sheets will usually specify the "mechanical life" of a relay which will give you a good idea of how long they will last. The typical mechanical life of a relay is usually 1 - 10 million operations. This may sound like a lot, and for most applications it probably is, but in this case the "buzzing" is cycling through a lot of operations. It may last for a while, but you will eventaully need to replace it. A "solid state" relay is not mechanical and will last much much longer. The only problem is, they are usually somewhat expensive.

 

[MansionHaunter]

This might work. I haven't tried it, but if my calculations are correct the values shown should work.

This is a very simple two-transistor circuit that will take the speaker-level audio output of some source like a stereo, radio, tape player or whatever and then dim the lights whenever the audio input increases. They should be full on all the time, until sound is played, when they should dim in accordance with the input level. The variable resistor is a level adjust to make it work with different output levels.

The light bulbs designed in are 5 to 10 watts each, and 12 V. This would assume you'd run it off of some 12V source capable of putting out at least 3 Amps.

 

[GOT]

Thanks! I will try it out right away and let you know if it works.

 

[GOT]

Sorry, I am new to electronics. What is the 22uF component represented with the two straight lines and the + sign?

 

[Otaku]

That would be a 22 microfarad electrolytic capacitor. When wiring this type of cap, be sure to keep the polarity correct as shown in the drawing. They tend to explode if polarity is reversed. Neat circuit, MansionHaunter - I'll have to try this one out, too!

 

[MansionHaunter]

Sorry about not labelling things better; the .1 uf is a ceramic capacitor, and the 22uf is an electrolytic. Everything should be available from Radio Shack.

One component change, though: the 2.4K resistor on the base of the 2n3904 to ground should instead be 6.8K, otherwise the incoming audio will not cause much change; the lights will rarely ever dim. On the transistors, the base lead is the one coming out to the left. The emitter is on the bottom right, with the arrow, and the collector is on the top right.

I'd try this on a solderless breadboard first before committing it to a prototype circuitboard using solder.

I might try it myself this weekend to get the values exactly right.

 

[GOT]

I have a 12V transformer that puts out 1 amp. Is that good enough or should I buy a different one?

 

[MansionHaunter]

1 Amp isn't enough to do much serious lighting; it'll light up a single 12v bulb to a decent degree, but for something that's going to be effective enough to fill a room with light you'll need more than that.

I'd suggest at least 3 Amps or better.

 

[GOT]

This will be a very small room (9' x 8') and I want it dim. I think one flashlight bulb would do, assuming it was brightly lit. Would the rest of the circuit work at 1 amp or would other adjustments need to be made? I am just trying to avoid additional cost here as well as I am not comfortable wiring up those transformers I saw at Radio Shack.

 

[heresjohnny]

MansionHaunter, this looks like a cool circuit. I may try to breadboard it this weekend if I can find the time and get the monster mud off my hands.

GOT, I also like to keep things dim, and I think you already have your answer from a previous post by MansionHaunter (1 Amp isn't enough to do much serious lighting; it'll light up a single 12v bulb to a decent degree), but I'll leave it to MansionHaunter to verify that .

 

[MansionHaunter]

1 Amp will work for dim light, and the circuit should work as shown, although I'll make the adjustment in the power input to see whether the values should change.

By the way - if you're starting with a 12V transformer, you'll need to rectify and smooth out the output to make it DC so the circuit will work at all.

The above circuit should do the trick.

 

[MansionHaunter]

whoops... my bad... I got the bridge hooked up backwards. Just a sec... that's better.
Radio Shack has an integrated bridge rectifier that will do the trick here.

 

[GOT]

Anyone breadboard this yet?