Lighting up the inside of a subwoofer

Repost to alt.binaries.schematic.electronic and I'll send you some info

you'd need one that rated for very high SPL.

???

parallel (with large resistors in series with your circuits input). problems most unlikely.

getting in series with the sort of current needed to put 500W into a 8 ohm load is'nt worth the bother,

google for colour organ.

Bye. Jasen

What is ECE? What year are you in?

John

Here's an interesting experiment you can try that may give you what you want with a bjt.

Wind some (10 ?) turns of hookup wire around one of the wires that connects the subwoofer speaker to the circutry that drives it to make a pickup coil. Then do this:

PNP + 12 --------------------- ---+ e\\ /c | - | ------ ----- | [1K] |Pickup|--|~ +|---[1K]---+ | | | | BR | a| [LED] | Coil |--|~ -|---+ [D1] | ------ ----- | | | | [D2] | | | | Gnd ----------------+------+----+

If the LED lights at all the levels of audio that you will use, you're in business. You can use the output at the collector to drive the gate of a mosfet, and switch however many LEDs or circuits you want.

Ed

If you wind turns around another wire, the coupling is zero.

This circuit blows out the PNP as soon as you turn on the +12.

John

Right. It is wound around one wire.

Thanks! Started with an NPN, then changed to PNP - forgot to chage the rest around. Correction:

PNP + 12 ---------------+------+---- ---+ | a| e\\ /c | | [D1] - | ------ ----- | | | [1K] |Pickup|--|~ +|---+ [D2] | | | | | BR | | | | | Coil |--|~ -|---[1K]---+-----+ | ------ ----- [LED] | Gnd ----------------------------------+

Still zero.

John

Thanks to both you and JL. So the experiment would fail, unless he did it like that.

Now the question is why is there 0 coupling? What do I need to read/study to gain the understanding you & JL have on this? I've got an incorrect idea(s), or a missing concept(s) somewhere.

Ed

Well, there's all that em field theory and stuff, but the simple statement is that parallel wires couple magnetically, and perpendicular ones don't.

And even if the wires are arranged to share flux loops, namely to couple, air-core coupling at audio:bass frequencies will be tiny.

The drive to the speakers is typically huge, so why not just drive the led's directly from the amp output?

Even better idea: stop doing silly light-organ tricks and spend the time studying electronics. If the op is a electronics student and can't figure out how to do this yet, he's in trouble.

John

One is as good as the other.

Bye. Jasen

It takes parallel (or atleast non-perpendicular) wires to make a (air-core) transformer if you wind the sense wire round the power wire your windings are mostly perpendicular to the otther wire and you won't pick much signal up.

Bye. Jasen