Steve,
1. Try something like this:

     (view only with fixed-pitch font)

                          +160VDC
                            |
                            |
                            x---x--------------x
                            |   |  /           |
                         [47K] /--             |
                            |   /\ 15V       S |
                            |   |           |--x P-channel MOSFET
                            x---x---------| |
                            |               |--x
                          [8K]               D |
                            |                  |
                            |                [ R limit]
        PIC               |/                   |
         o-----[Rg/Rb]----|                    |
                          |\E               {lots of LEDs}
                            |                  |
                            |                  |
         0V-----------------x------------------x

You can use your BS170 to drive the power fet or just a generic NPN.
Don't forget a clamping diode on the base / gate of the npn / nchannel.
I use this a lot for driving LEDs, but the voltage source is only 12V.

2. If you can, switch over to just an N channel power fet and sink the
load.  Fewer parts.

Bill

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Steven Kosmerchock
Sent: Friday, March 19, 2004 11:43 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: [EE]:Urgent help needed with high voltage logic switch.


PICListers,

I am in urgent need of some help. I need to switch a 160V DC @150mA
signal (hopefully with PWM around 100Hz) using a PIC I/O. The solution I
had, which I have used for up to 50V DC @ 5A was like a 4th of July
celebration when hooked up to the 160V DC. It is basically being used to
power up a "alot" of LEDs in series, I can't go into further details. I
was thinking of using a circuit similar to the one linked below, any
other recommendations would be greatly appreciated! High voltage
switching isn't my thing, so any help would be wonderful.

http://www.geocities.com/researchtriangle/lab/6584/high_v_switch.bmp

Thanks.
Steve

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