Generator Monitor

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agronaught
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Generator Monitor

Post by agronaught » Sun Nov 06, 2011 9:09 pm

This is possibly as simple as an arduino project can get.

I have an emergency generator at work which works well, automatically starting on power outages etc. The problem is that the generator is on level 27 of the building, and access during a power outage requires a trip to the sub basement to get a key from security (19 levels) and then back to level 27... a lot of stairs. I also wanted a way to remotely check the generator status and to monitor the run times so we can keep track of the diesel usage without the costs associated with full remote telemetry.

The solution was built in under an hour using off the shelf parts, namely:

+ 1 * arduino duamilanove
+ 1 * freetronics POE Ethernet shield
+ 1 * freetronics 802.3af POE module
+ miscellaneous collection of smd resistors etc.

The sensor caters for a hard wire from two relays in the generator control system which are switched when the generator is running. These relays are NC (normally closed) and NO (normally open) and using both provides for the system run state (running/not running) and fault detection (inconsistent state/broken wire etc).

A secondary sensor has been added which 'listens' for the generator. The initial version used a piezo element which worked but only just. A second revision of this sensor will use an electret microphone and Op-Amp for a little more sensitivity.

The sensor is powered via power over ethernet, uses the local NTP server for time, supports remote status enquiry via HTTP and sends alerts to our monitoring system via UDP. The monitoring system responds to state changes and tracks the generator run times (hours) to provide some remote fuel monitoring capability.

All in all an extremely simple sensor, made easier due to the availability of off the shelf components.

Image
Image

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jonoxer
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Re: Generator Monitor

Post by jonoxer » Mon Nov 07, 2011 9:53 pm

Don't undersell what you've created: this is great! It's an elegant solution to a real-world problem. I'm sure that if you put your code and a bit more detail up online (particularly how you connected the microphone to detect operation of the generator) there would be many people who would be interested in it. Perhaps you could expand on it a bit in this thread.
--
Jon

sawtellda
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Re: Generator Monitor

Post by sawtellda » Mon Nov 07, 2011 11:13 pm

What a clever lateral solution! $100 worth of VOX as opposed to a trail of emails a foot thick trying to sort the politics of getting a simple status interface contact. De Bono would be proud.

I too would like to see some more detail of your project, but in the meantime I might just pinch your clever idea for application in some other systems.

agronaught
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Re: Generator Monitor

Post by agronaught » Tue Nov 08, 2011 2:04 am

Thanks :)

I'm still finalising the electret interface and hope to solder up a prototype tonight. My plan is to use a suitable op-amp as a non inverting amplifier to amplify the small signal from the electret, and a comparator to toggle the 5v supply to a pin on the arduino when the preset threshold is crossed. Pot's on the amplifier and comparator will allow for fine tuning of the gain and thresholds.

An LM324 is probably all that's needed and hopefully I can pick up a couple from jaycar today so I can finish this, I'll post an update and the code once done. Then all I need to to is resist the temptation to embellish the design (temperature sensors, fuel/volatiles sensor, CO sensor...).

Cheers
Jason.

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jonoxer
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Re: Generator Monitor

Post by jonoxer » Tue Nov 08, 2011 4:36 am

Regarding the electret - hmmm, maybe you could wait a couple of weeks? We're about to release a whole range of new modules, and one of them is a microphone module with an onboard pre-amp. Marc has designed it to provide two outputs: one providing the raw audio waveform, and one providing the sound pressure level (SPL). It would be *perfect* for your application. This is the first time we've ever mentioned it in public so you have a bit of a scoop here, but this is what it will look like:

Image

That's a hand-soldered prototype so please excuse the finish on the joints. Besides, it's a seriously small device! You can see outputs on the bottom labeled "MIC" and "SPL", which are audio and sound pressure level outputs. On the top right you can also see an LED labeled "DETECT", which is linked to the SPL output and illuminates proportionally to detected sound pressure. Perfect for quick visual feedback that it's picking something up.
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Jon

agronaught
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Re: Generator Monitor

Post by agronaught » Tue Nov 08, 2011 4:53 am

You never fail to amuse Jon. This looks like a great little module and I'll happily test it for you ;)

I'll continue with the prototype for now as there is a scheduled power outage in the next couple of weeks -- a chance to test the system in a real usage scenario. However as your developing a module I'll stick to proto board and look to replace the sensor when the new module is available.

Besides - it's a chance to play with opamps ;)

Cheers
J.

EpicTinker
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Re: Generator Monitor

Post by EpicTinker » Tue Nov 08, 2011 7:42 pm

That's awesome, Jon! Can't wait to see the other modules!

agronaught
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Re: Generator Monitor

Post by agronaught » Mon Nov 28, 2011 4:48 am

Any update on the sound sensor John ? Happy to 'test' it for you ;)

I've been delayed in my prototype - home rennovations... <sigh>. Hope to see you at LCA!

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jonoxer
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Re: Generator Monitor

Post by jonoxer » Mon Nov 28, 2011 11:11 am

Our first production batch has just been completed, and Marc is checking them over right at this moment. As soon as it's all verified we'll be making them available on the site! We're just minutes away :-)
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Jon

agronaught
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Re: Generator Monitor

Post by agronaught » Mon Nov 28, 2011 11:44 pm

Sweet :) just ordered a couple. One for this project, one for the highly contraversial 'Early Morning TV volume control' to be implemented to prevent the kiddies from waking me up in the morning ;)

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