How to add 12v lamps to circuit?

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

 

[ehsjr]

shobley@userfs.com wrote:

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

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

 

[Kasterborus]

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

 

[Kasterborus]

On Jul 30, 10:57 am, Kasterborus <kasterbo...@yahoo.com> wrote:

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?