Why you don=B4t use a P channel mosfet?
Try with 12PF06 and a simple V divider and one npn to switch the mosfet on =
and off.

Pablo Ginhson







> From: info@datech.se
> To: piclist@mit.edu
> Subject: Relay replacement (High side switch)
> Date: Sun, 12 Oct 2008 01:44:09 +0200
> =

> Hi, I am trying to build a high side switch as a replacement
> for an old relay using a PNP transistor. The load must be driven =

> from 24vdc comming from the relay then back through GND. The =

> coil was driven by 24v then to GND.
> =

> See attached schematic.
> I got the PNP switch working. If the base floats or
> is connected to GND the output is off. When its connected =

> to 24v the load is switched on. So far so good. =

> =

> Unfortunately that is the opposite of what is needed so =

> therefore I added the NPN inverter which works fine by itself. =

> The problem comes when the two circuits is connected toghether. =

> The PNP doesnt switch off when its connected to the NPN inverter.
> =

> Why doesnt this work, what is needed to make the PNP switch =

> off by the NPN ?
> =

> If there is some major problem with my approach I am open for
> other solutions. This is a one off btw.

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