Since I'm not an engineer, I wonder if someone can tell me
what to buy to record the transition of a 110vac circuit
from on to off and vice versa several times a day over a
period as long as is practical based on the recorder
limitations. We wish to end up with records every day for a
year or more. If the device could record for a week without
operator attention that would be helpful.
You may already have one. Using a suitable spare computer (say a laptop
running XP) plugged into a good supply, connect it to a hub/switch
plugged into the supply that you want to monitor. Set the correct level
of audit for system events. You will then get TCP entries in the event
log (Events 4201/4202 with XP) every time the power fails on the
hub/switch and is restored. Filter the log for those events and you will
have a complete history of on/off supply transitions.
You can set traps on those events, to carry out actions such as
generating messages, emails, start other systems, sound alarms, etc. You
can monitor the events remotely - eg over the internet..
A very cheap and effective way of, say, monitoring when and for how long
something runs (eg a water pump) - even wirelessly, if the hub/switch is
Set the log file appropriately and you can record for years and years..
Another of my little secrets given away.... ;)
Thank you for sharing this secret. I think this is what's
needed. Would you share another secret with this neophyte?
Could you provide a bit more detail about "hub/switch," what
it is and how I would connect it to the XP computer?
This is an example:
It connects via an ethernet cable, such as this:
Notice that the total cost is opnly a few pounds.
The hub/switch is a device normally used to connect computers together
into a local area network. However, once connected, if it loses power
and stops working, this is detected by the computer(s) connected to it.
When it gets power back, this is also detected by the computer(s).
In this case, the hub/switch is not being used to connect computers, but
is being used purely to give the computer a way of sensing when the
power supply (into which the mains adapter of the hub/switch is
plugged), is interrupted and restored.
Many operating systems, Windows XP included, log events such as the loss
of connection mentioned above. It is then fairly easy to extract the
times of all the power losses and power resumes, from the event log.
Windows XP gives tools for doing that. Plus allows you to trigger
things, such as sending an email, whenever an event (or particular
I don't know if this can be any useful, but I know of 12v mechanical
counters that step up 1 digit every time they receive a 12v dc pulse at
I would connect a little delay relay circuit, like those used for
obtaining a couple of seconds delay before connecting the speakers to a
Of course I'd use it in reverse mode, connecting in line the relay
contact that is ON when the power is off.
So, when the 110v or 220v line comes back, it will power a transformer
(with a 12v dc output) to generate a pulse for the counter, that ends
when the relay switches on (after 2 seconds). And when the mains power
goes off, it all starts again...
An alternative would be to use a little LCD digital counter, but it must
stay always powered on (e.g. battery-powered).
The count pulse could be easily generated with a 110v or 220v ac relay,
using one of its contacts to send the appropriate voltage reference to
the counter input...
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