Hmmm... zener you say, huh.... I'll have to try this. Thanks.



Marcos Fabricio Bezerra wrote:
> 
> Hi, Neil.
> Beside changing the R2 position, you can use a series zener diode
> connected 
> to R1 and I/O pin. I think that a 9V1 would do the trick.
> Cheers,
> Fabricio.
> 
> 
> 
> ----- Original Message ----- 
> From: "PicDude" <picdude2@avn-tech.com>
> To: <piclist@mit.edu>
> Sent: Wednesday, June 11, 2008 1:53 PM
> Subject: [PIC] +12V high-side transistor switch?
> 
> 
>>
>> I need to switch on/off a 12V load, high-side, from a PIC running on 5V, 
>> and
>> tried this circuit, but the output is always on.  With the PIC I/O 
>> floating
>> (set as input), the load should be switched off, and with the I/O low,
>> the
>> load should be switched on.  I'm using 1k for R1 and 10K for R2.  The
>> load
>> will be up to ~250mA, btw.
>>
>> Any idea what I'm doing wrong here?  The circuit...
>> http://www.narwani.net/neil/electronics/PIC-HS12VSwitch-01.gif
>>
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