How to add 12v lamps to circuit?

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shobley@userfs.com - 29 Jul 2008 04:09 GMT

http://www.stephenhobley.com/sound.jpg

I have this circuit, the standard Velleman mk103 sound to light kit. I
would like to control 2 20w 12v lamps. I've got some TIP142
transistors that should be OK to do the switching, I just don't know
how to tap into the output to make it work.

I've been trying to tap just before the first LED but this is giving a
very limited response.

What's the best way to do it?

Steve

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ehsjr - 29 Jul 2008 21:15 GMT

> http://www.stephenhobley.com/sound.jpg
>
[quoted text clipped - 9 lines]
>
> Steve

Come off the collector of T4 on the existing circuit
through 1K to an optoisolator. Use that to turn the
TIP142 on/off:

4N25 +--------------+--- +13.2
------ | |
T4---[1K]---|1 6| [4.7K] |
| | | /e
Gnd(9V)-----|2 5|---+---[470R]---| TIP142
| | \c
|3 4|---+ |
------ | |
| [Lights]
| |
+--------------+--- Gnd(13.2V)

Shown is a 13.2 volt supply for the lights to make up
for the voltage drop in the TIP42.

Ed

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Kasterborus - 30 Jul 2008 15:57 GMT

Thanks for your help - I will try this...

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Kasterborus - 30 Jul 2008 16:13 GMT

> Thanks for your help - I will try this...

I only have the 4n29 - which appears to be a darlington arrangement -
this should drop right in to replace the '25 - correct?

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Electronics Forum / Basics / July 2008

How to add 12v lamps to circuit?