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gardenyu wrote:
> =20
> First time user, thank you for any suggestion:
> =20
> =20
>     We have a motor controller built here: there are two turn-on and fw=
d/rvs press buttons on a case top, which connects to the PCB inside via s=
ome signal cable. The input to the board is 110V AC, since there is no ea=
rth ground presents, the high and low input voltage could float to higher=
 than 110.
> =20
>     The problem is: if the buttons are somehow shorted to earth ground =
at the case top (even if we have built almost perfect insulation on the c=
hassis), there will be about 40mA comes from the switch button, goes thro=
ugh human body, which kills. Is there anything we can do to this situatio=
n?=20
> =20
>     I'm just a junior engineer, so it might seems a stupid question to =
you guys, but thank you very much for any help.
> =20
> =20
> =20
> _________________________________________________________________
> MSN=CA=A5=B5=AE=C0=F1=CE=EF=BB=F0=C8=C8=B5=C7=B3=A1=A3=AC=C3=E2=B7=D1=B7=
=A2=B7=C5=D6=D0=A3=AC=BF=EC=C0=B4=C1=EC=C8=A1=B0=C9=A3=A1
> http://im.live.cn/emoticons/?ID=3D18
I think you need to study this more closely and locate the electrical
short first.
This condition could be a killer if ignored.

Simply disconnect everything, then reinstall one item at a time until
the fault is located.

--Bob A



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