> Has anyone ever built a cable for the 400 model that
> uses more than three pins?
> I just put one together with the help from the BUPS-HOWTO,
> thanks guys!!
> But going back to the doc that came with the UPS, it talks
> about 4 additional pins, one of which looks like it could be
> used to tell the the battery is getting low and shutdown will
> occur in 2 or 5 minutes (depending on a dip switch setting).
> My problems is that I know squat about electronics and have
> trouble interpreting the following:
> 6.4.1 Outputs at pins 3, 5 and 6 are actually open collector
> outputs which must be pulled to a common refereced supply no greater
> than +40 Vdc. The transistors are capable of a maximum non-inductive
> load of 25 mAdc. Use only pin 4 as the common.
That means that in order for those three output pins to work,
you install "pullup" resistors or other suitable devices,
from the pin to a voltage of not over +40 volts. If you
are using regular TTL, you will want to limit your voltage to
5-volts, if you are going into a serial port DATA line (not
a handshake line), you would use 12 volts. The resistors
would limit the current to not over 25 ma. Since most likely
you will use your pins to drive some port in your computer,
then 5-volt TTL levels are adequate. Your PC power supply
RED wire is +5 volts, and the black wires are GROUND.
Your pullup resistors should be at LEAST 220 ohms, 1/4 watt.
I would use more, as at that resistance, your transistors will
be running full bore. Say you use 680 ohms, or even 1,000
ohms. Connect one end of the resistor to 5 volts, the other
end to the pin in question. When the APC is not sending
anything to the pin, the voltage at the pin will be 5 volts.
When a signal is sent, the transistor conducts heavily; the
voltage at the pin will drop to under 0.3 volts. You can
measure this with a voltmeter.
If you are hooking up to a relay, then the hookup is a bit
different. First, you need a 5-volt (or 12 volt) relay of
appropiate coil resistance. For 5 volts, 220 ohms is
minimum, more is better up to 1000 ohms. For 12 volts,
minimum resistance is 500 ohms, maximum 2000 ohms. You
cannot use an external resistor to add resistance to a low
ohm relay. You will also need a little diode across the
relay coil to prevent inductive voltage spikes which will
blow your transistors. Use 1N1001 power diodes, about
10 cents each, and hook the Anode end to the transistor
connection (pin) and the cathode end to the 5 or 12 volt
end of the coil. The cathode end is labeled with a Band
on the body of the diode.
The hookup looks like this. The coil has two wires. They
are reversible. Connect your diode across these two wires
(or pins, whatever). When you finish, the junction of the
coil and the one diode end with the band goes to the power
supply, the other end to the APC pin. A relay is a little
electromagnet that when energized pulls in a metal bar that
can make or break a number of switch contacts. Relays
are easy to get in spst, spdt, dpdt and dpst. This means
single pole, single throw; single pole, double throw, etc.
A single pole, double pole is like this. When the relay is
unenergized, the "pole" is hooked up to one of the "throws".
The other "throw" is disconnected. This is a switch turned
on between the pole and the normally closed (NC) throw.
When energized, the pole disconnects from the NC throw, and
now hooks up to the normally open NO throw.
Throws are labelled NO, NC and the poles are C for common.
Most relays have a diagram of which pin or wire corresponds
to what, and you can get suitable relays and diodes at
Radio Shack. All designations of NO and NC are with the relay
de-energized. Relay contacts can handle from about 0.1
ampere up to whatever you want. Little ones as will be used
in this application will probably handle no more than about
2 amperes. If you need more, you can use the small relay to
in turn energize a larger relay that can handle from 2 up
to thousands of amperes. Usually, two relays in tandem are
not used much these days, the trend being to use the APC
pins to drive a larger transistor which in turn will activate
a larger relay.
The Linux power fail software takes care of contact debounce.
This means that when a mechanical switch or relay makes contact,
there is a microscopic bounce to the contacts. Instead of a
clean ON or OFF condition, there are maybe a few hundred such
connections....at computer speeds, this can be interpreted
as a few hundred activations. Keyboards were notorious for
this in the old days, you pressed the letter "A", and the
monitor would show "AAAAAAAAAA" <grin>. Solid state
computer equipment hhhhaaaaaasssss iiiimmmmmppppprrrrooovvvveeeedddd!
Ramon Gandia Please address e-mail replies
Nome, Alaska to rfg _AT_ nome.net.