Re: CAN Bus protection (100VDC)
- From: Paul Keinanen <keinanen@xxxxxx>
- Date: Wed, 27 Sep 2006 22:23:03 +0300
On 27 Sep 2006 10:24:33 -0700, "StanV" <jonsquire2000@xxxxxxxxxxx>
wrote:
We designed a machine where we have at some place the CAN-bus signals
and HighVoltage power (100VDC and 220VAC) on the same cable.
What kind of fuses do you have feeding the 100 V and 230 V lines ?
If we are talking of only a few amperes, connect one reverse biased
rectifier diode from Gnd to CAN_H and an other from Can_H to Vcc rated
for at least a few times the fuse rating. Do the same for CAN_L. Put a
5.5 V 30 W zener between Vcc and Gnd. Assuming the logic Gnd is
connected to the 100 Vdc and 230 Vac ground/neutral, this will blow a
1-5 A fuse in the 100 or 230 V feed.
This will remove the offending voltage from the system. Unfortunately,
the large rectifier diodes have a quite large capacitance, but putting
2-3 in series will reduce it, but of course the clamp voltage will
increase.
If the high power circuit has larger fuses, then you would have to put
a fuse (maybe 100 mA) in series with CAN_H and CAN_L on _each_ node
and use smaller rectifier diodes rated about 1 A to Vcc and Gnd, thus,
the stray capacitances would be lower. A 5.5 V 1 W zener between Vcc
and Gnd should be sufficient.
This circuit will blow the series fuses when the CAN nodes, but it
does not disconnect the high power supply, so you may be zapped by
dangerous voltages, when you try to figure out, why there is no
traffic on the CAN bus :-).
Paul
.
- References:
- CAN Bus protection (100VDC)
- From: StanV
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