Software & Firmware for FlexNet

FLEXNET ON EMERGENCY POWER

-----Original Message-----
From: Dave Packard
Sent: Sunday, May 20, 2001 1:18 PM
To: Bob Anderson; John Papson
Cc: John Kushneir (K2JFK); John Driscoll N2MKH; Jim Wzorek
Subject: flex query

Hi guys.

K2JFK and I were discussing emergency power for our packet nodes, when John brought up the question of how one could supply enough power to a computer in a FlexNet node during a power outage. We understand the advantages Flex has over NetROM in recovering from a power failure, but much of the interest in packet up this way relates to emergency communications.

An off-the-cuff estimate of the power requirements of a 386/486 computer sounded like a lot of current drain for a back-up battery. Most of our nodes are on deep cycle battery backup for short interruptions and manual start gasoline generators for any outage that lasts about 12 hours or more.

Have you had any experience along these lines? Comments? Regards,

Dave

K1YHR.

Hello All:

Yes, computer does draw more power, but overall improvement of FlexNet outweighs this concern. FlexNet's major benefit being it's ability to automatically route around node site and link failures.

One has to ask oneself, how often does a momentary power blink extend beyond an hour or two ? What we have found is that there is never enough battery for a real emergency, such as a hurricane or ice storm. We also found that 15 minutes of backup carries us for months on end.. The "up time" in the "ST"atus dump shows how long a node has been continuously running.

Backup time can be maximized by careful hardware selection.
Trick is to find computers that draw a minimal amount of power.

1) First off a keyboard draws power and is not needed...

2) Use a PC with a highly integrated motherboard, one with large IC's.
Also look for one WITHOUT a big heatsink on the processor IC..
Later 386 boards with about 5 big IC's and plastic 386SX processor.
386SX20's work fine for moderate size node stacks. Use of 16550
UART serial cards out weighs need for a super fast PC !

3) Finally, load the computer with the minimum amount of memory,
1 meg for a small node, 2 megs for a large multiport site.
Use newer memory such as SIMM's, modern memory draws less per
megabit than older !

4) Check the label on the hard drive, some draw a lot more power then others ! (always use IDE hard drives, old MFM and RLL drives are power hungry and plain unreliable !) It is possible to replace the hard drive with a "flash card" and small adapter board. A Flashcard has an identical electrical interface as an IDE hard drive. TAPR has a kit for the Flashcard to IDE adapters.

5) It's possible to remove fan, saving more, requires testing before doing..
One can glue heatsinks to all the chips, and let PC convection cool.

6) The floppy can also be disconnected as it also is not needed. Leave it in the machine, just unplug both the power and data cables !
That way it is available if needed for an update or something..

7) Or it is possible to run FlexNet from a Floppy drive, forgetting about
a hard drive all together. (I prefer a hard drive over a floppy, HD's are
sealed, floppy's collect dust and dirt.)

8) If you want to run a DXCluster, BBS, or whatever at a remote site,
that can be in a big fast computer linked to main node computer.
Hence the node computer can be a slower lower power unit...
Battery backup only the node computer, and forget about the frills
running in the big power hungry computer in time of emergency!

I've measured several typical 386SX20 machines, and they all draw under 50 watts, with fan, floppy and keyboard enabled.. (when one adds up how much power all the TNC's and radios draw when passing traffic, it will most likely greatly exceed the PC power drain !)

A small UPS with a marine deep cycle gel battery will keep the PC running for hours! Don't forget that most UPS's are designed to keep the monitor running to allow user to shut down. No monitor is needed for a remote site, extending backup by a factor of 4 or more !

A more expensive solution is to use a "Single Board Computer" (SBC) running off of a small 5 volt supply... These typically have built in DOS on a chip, and can run FlexNet out of a Flash ROM. A small one chip switching supply can convert 12 volt battery to 5 volts for the SBC. I have a couple that draw less than 5 watts!

Finally, an older Laptop or Notebook PC can also serve remote site. You may be limited to a single serial port, but can drive four 1200 baud links by daisy chaining TNC's RS-232 at 9600 baud... Laptops have the best designed in power management. We have these now running at two sites, one with the display (was busted) and backlight totally removed.

73 John WB2CIK

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