aspa
Posts: 2
Joined: Thu Apr 21, 2016 7:08 pm

Monitoring electrical device activation times

Thu Apr 21, 2016 7:33 pm

Hi,

I'm interested in building a system for monitoring activation of three different electrical devices, that is, when and for how long the different devices are activated. Being able to monitor electricity consumption would be an added bonus, but monitoring activation is the main goal.

Any advice on how to build such a system and what kinds of sensors and other components could be used to build this?

I'm a software engineer, but have no experience in electrical engineering, so solutions that don't involve advanced or high-voltage electrical installations would be preferred.

Marko

thermo
Posts: 12
Joined: Fri Mar 25, 2016 4:55 pm

Re: Monitoring electrical device activation times

Fri Apr 22, 2016 4:22 pm

If I was doing this I'd use something like this:
https://www.sparkfun.com/products/11005
Then use some sort of analog=>digital converter.

The sensor detects a current by induction. There may be other ways for your situation.

aspa
Posts: 2
Joined: Thu Apr 21, 2016 7:08 pm

Re: Monitoring electrical device activation times

Fri Apr 22, 2016 4:43 pm

Yes, that looks like a feasible method for current sensing in my case, thanks!

Do I need to reduce the current / voltage somehow before plugging it to RasPI?

Can you recommend a analog-digital converter that would support multiple inputs and outputs and be supported by Linux kernel, so that I would get the signal delivered to my user-space program?

thermo
Posts: 12
Joined: Fri Mar 25, 2016 4:55 pm

Re: Monitoring electrical device activation times

Fri Apr 22, 2016 6:45 pm

aspa wrote:Do I need to reduce the current / voltage somehow before plugging it to RasPI?
Sorry, I don't know. You would need to check the data sheet/specs of the sensor you choose. It is likely the output voltage & current from an inductive sensor would be human-safe. Pi-safe is another matter.
aspa wrote:Can you recommend a analog-digital converter that would support multiple inputs and outputs and be supported by Linux kernel, so that I would get the signal delivered to my user-space program?
The MCP3008 seems to be popular & well supported.
http://www.raspberrypi-spy.co.uk/2013/1 ... n-mcp3008/
There are other examples.

grahamed
Posts: 277
Joined: Mon Jan 30, 2012 7:01 pm

Re: Monitoring electrical device activation times

Sat Apr 23, 2016 2:17 pm

Hi

The sensor is a current transformer (CT).

The CT produces a secondary (output) current proportional to the primary current according to the turns ratio. In this case 1:2000 so 30A will give 15mA in the secondary. The user must choose a suitable resistor to convert this current into a voltage. 1k would give 15V, etc.

Please do a search for the dangers of un-terminated CTs - and note that this device plugs/unplugs.

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