len@rufus.math.nwu.edu (Len Evens) (05/31/89)
We have twice within the last year sustained lightning damage to terminals and other devices connected through twisted pair wiring (internal to our building) to ALM boards on our Suns. Also, the ALM boards themselves seemed to have sustained some damage. The wiring has been set up and is maintained by our local university telephone company. We don't believe there was any damage attributable to surges coming through the power lines. Does anyone have any similar experiences, and can anyone suggest countermeasures? We have about 30 such connections so we want to keep the cost down. Leonard Evens len@math.nwu.edu Department of Mathematics Northwestern University Evanston, IL 60208 312-491-5537
pearce@tycho.yerkes.uchicago.edu (Eric C. Pearce) (06/09/89)
We had similar problems (lightning zapping RS232 lines) on lines inside
our building, on both the CPU (ttya and ttyb) and the ALM. We now have
all our lines (both ends) protected with General Semiconductor "CPP-52"
lightning protectors. They go for about $39 each, are based on Si
avalanche diodes and have a separate ground wire. They provide secondary
level protection with the following specs (from Gen. Semi.):
Max. transient voltage: 2.5 KV lightning
40 KV static discharge
Maximum transient current (8 x 20 usec): 190 A
Maximum clamping voltage @ 75A (8 x 20 usec): 40 V
Protection clamping time: less than 10 nsec
We have not had a failure since installing them (although we have had
other non-protected equipment get zapped and several bad storms.)
The Gen. Semi. GSI Product Data Book also had lots of other transient
voltage suppressors and a nice Application Note on protecting computer
data lines in general.
- Eric C. Pearce
Yerkes Observatory, University of Chicago.
e-mail: pearce@tycho.yerkes.uchicago.edu, pearce@oddjob.uchicago.edu
fax: (414) 245-9125