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Newb questions about external dataloggers


(Tom Lang) #1

Hi all,
I’m updating an educational exhibit, where kids ride bikes to generate power. Currently we’re logging the generation but not the consumption. The generation is logged with a PET-7017 datalogger and output directly to a PC over ethernet.

I’m thinking of using an EmonPi to measure the power consumption of the classroom, and use emonCMS to graph it against the bike generation data

Is it easy to connect the data from an external datalogger into EmonCMS? And can the EmonPi connect directly to a PC, or does it require net connection?

Thanks for any help. I’m extremely new to all things datalogging and pi but I’m a fast learner. Just need to work out what I need to learn.

(This is the metering setup. those 9 grey cables lead to the bike generators. The datalogger is at the bottom left)


(Robert Wall) #2

How long is your piece of string? It all depends on whether you’re able to program the data logger to send the output that emonCMS/emonHub expects, or whether you can write a script in your PC to parse and format the data that the datalogger sends. And that might mean picking the data apart to determine the format, if it’s not documented somewhere.

The latest Pi has WiFi, so a LAN connection is all but automatic if you have a WAP within range, but I believe it’s possible to use a serial connection.


(Tom Lang) #3

Thanks Robert. I guess I’m still trying to figure out the best hardware/software for my needs.
Having a poke around on EmonCMS, it looks like it’s all web-based, which means I probably can’t use it (the classroom is not connected).
The EmonPi looks like a great piece of equipment, but I guess that will depend on if I can easily feed its data into another program.


(Robert Wall) #4

“Web”, as in LAN. If you have a router, that’s all you need. It only needs a connection to the outside world to be updated.

If that’s all you want to do, then the emonTx is the answer. It has the same energy-measuring front end, but with 4 channels. It’s a lot easier to program, and it does have the FTDI serial output (to USB via the programmer) that you plug into a PC.


(Tom Lang) #5

Ah, great, so the emonTx feeds data into emonCMS running on the PC. That makes a lot of sense, thanks.

And it looks like my other datalogger is outputting over Modbus. So once I can work out how to hook that into EmonCMS, I’m in business. Node Red sounds promising.


(Bill Thomson) #6

Hi Tom,

A forum search for modbus will return a few threads on how other users have interfaced modbus
instruments to emonCMS and other data collection apps.


(Robert Wall) #7

You can certainly run emonCMS on a PC. Obviously, it must run continuously in order to log continuously (the emonTx does NOT store any data at all), and you’ll need to set up a WAMP stack - assuming it’s a Windows OS on the PC.

I did a write-up on setting up WAMP, but I’ve moved over to Linux and it’s several years out of date, but it might help. I think it’s now here: https://github.com/emoncms/emoncms/blob/master/docs/WindowsInstall.md - it looks familiar!