Re: AC spike go pass XFRM and regulator to reset CPU!!??
- From: CBFalconer <cbfalconer@xxxxxxxxx>
- Date: Fri, 25 Apr 2008 09:43:39 -0400
Rodo wrote:
I have a device that is powered by 240VAC (also works from 120VAC).
The AC drives the primary of a transformer (with a fuse and a MOV).
There is also a fan connected to the 240VAC with a switch. The
secondary of the transformer has a bridge, a large electrolytic cap
(1000uF/25v) and an LM7805 regulator. There is a smaller cap
(10uF/10v and 01uF/25v) at the output of the LM7805. Then the 5vdc
connects to a PIC.
Almost every time I flip the fan switch a spike shows up at the
output of the regulator. This is the part that I mostly do not get:
even if I disconnect the fan and I flip the switch... the spike
shows up ... and it is a bit larger in amplitude. I grabbed a
picture of the spike ... you can see it at:
http://mysite.verizon.net/rodo/ds0000.bmp
You don't seem to be getting many (in fact zero) answers. I
suspect the reason is the same as mine, bafflement. Without the
claim that it happens with the fan disconnected I could come up
with several attacks, but as it is you seem to just be flipping a
totally disconnected switch.
--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.
** Posted from http://www.teranews.com **
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