Experimental Physics and
Industrial Control System

Emmanuel Mayssat <[email protected]> · Mon, 17 Sep 2007 15:12:15 -0700

John,

There are several issues with power cycling all of which I experienced
at one point.

1/ The operator needs to know which unit to power cycle. Given the
distributed nature of EPICS, this may not be obvious.
2/ During power cycle procedure you do not have any control, so the
synchrotron is in an unknown, uncontrollable state which is exactly what
I want to avoid.
3/ A power cycle resets all output signals (to zero) even if they are
later restored to their previous values. This is particularly true for
DAC PCI cards with AO and BO. 

In the past and for other reasons, I looked at those networked power
strips (a.k.a PDU or power distribution unit). The company called Server
Technology (http://www.servertech.com) had some impressive products.
Their products are designed for rack mountable equipment up to
22kW/30A. 

A console server would be a great complement as well. But PDU and
console servers do not guarantee I know the state of my synchrotron at
all time. 

Regards,

--
E

On Sat, 2007-09-15 at 09:08 -0400, John Sinclair wrote:
> Emmanuel,
> 
> I, for one, never rely on an EPICS IOC to protect property or personnel. 
> If an IOC
> experiences a software-related lock-up, I cycle its power. If it resides 
> in an
> inaccessible location, I connect to a special network-attached device 
> via telnet
> to perform the power cycle. In the worst case, this causes a small change in
> some output (values are saved every ten seconds so we can loose a change
> that occurs immediately before the failure).
> 
> John Sinclair

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System