Monitoring 110v AC

[bwinkler]

I'm planning to set up a 1-wire network to monitor the temperature and HVAC in my server room.

I'd also like to monitor whether our backup generator is running and I'm wondering if the HVAC monitor could be modified to check for 110v AC on one or more of it's channels.

I'm not an EE by any stretch of the imagination, but it seems like it wouldn't be too hard a mod.

Any suggestions?

 

[sbessel]

I use an old 12vdc wall wart (transformer) connected to a 12v relay, I then connect the relay to my Ocelot and whenever the power goes out, the relay turns off and my Ocelot says the power is out.
This had the advantage as I had all the parts laying around, and there is a small buffer built in with the wall wart that stops me from getting notified on every small glitch.

I am sure you could do the same with 1-wire, try using a MD3014/DS2405, it should work the same, I tried one quite a while ago, but for my use they were too slow. Check out http://www.midondesign.com/ they have a lot of sensors, and FAQ's that may help.

 

[elcano]

A 120v relay from Radio Shack also works. In case you dont have the transformer - and might be more power efficient.

 

[damage]

i assume you have a ups in your server room. ups monitoring software bundled with the ups usually can execute scripts/programs on power fail...

 

[bwinkler]

We have UPSs to handle outages in the short term and a generator for when the power is out for longer.

The UPS notifies me when the power goes out, but it doesn't know the difference between when the generator kicks in (on an automatic transfer switch) or when the main power has been restored.

I like the wall wart idea, sbessel. It's simple and flexible. Thanks!

 

[sbessel]

A 120v relay from Radio Shack also works. In case you dont have the transformer - and might be more power efficient.

I tried that, except I kept getting alerted on little power 'blips' - so I went the 12v method, the wall wart hold the relay open for a good 3 seconds without power.

Plus I had a relay and wall wart, so no extra expense.

I also did try the UPS monitoring but it was a pain in the butt... so I gave up, i like to use the KISS process whenever possible.

 

[BraveSirRobbin]

Since he wants to use the one-wire maybe consider THIS board which lists "two analog inputs". Then just connect a wall wart up to it with a DC output within the analog inputs monitoring specs.

Another thing you can do is monitor current via a CR Magnetics current sensor and possibly read the actual current being drawn (again, don't know the specs of that analog input capability).

I find that site difficult to figure anything out (specs, etc...) so maybe someone more knowledgeable on one-wire can offer some guidance.

 

[smee]

Here is another example of a sensor/approach that can be used to sense AC power (from the CT How-Tos):

AC power on/off sensor, A sensor module with variable resistance

How to monitor the status of a device using its status light

I'm not sure how it will handle power blips.

 

[ericvic]

Using the wall wart with the HVAC Monitor would work fine.

I had never thought of using wall warts. Scott thank for the great idea.

Eric