Hello,
Has anyone considered the possiblity of powering an open energy monitor component from some sort of induction loop on the mains cable itself? It may well be a crazy and dangerous idea but I am a physicist and not an engineer so the pretty little universe I perceive might not be what is actually found in reality!]
I'm going to build an energy monitor setup at some point and I don't like the idea of powering it using batteries - I'd prefer a completely hands-free solution that I can forget about. You can of course use a USB mains adapter but most electricity meters are in a cupboard or small room without a nearby plug.
So my idea is to use some sort of coil wrapped around a mains cable to power the device. Is this at all feasible? Am I being completely insane? As far as I am concerned it would just take the right number of windings with the right kind of cable to produce the correct voltage for the system to operate. Are there risks involved with this approach, such as fire, heat, chemical reactions or anything?
I look forward to seeing my idea shot down promptly!
Re: Alternative Power Supply
The onzo energy monitor harvests power from the CT, enough to power its wireless link:
http://onzo.com/for-utilities/solutions/data-capture-and-return/
Re: Alternative Power Supply
Thanks! That proves it's possible, at least. They seem to use a rechargable battery to power the device which harvests power from the mains. Does anyone know if it would be possible to get a similar solution working for the emonTx?
Presumably the rechargable battery is used for something - probably to provide a DC output to power the circuitry? (It makes no sense in it being there for redundancy - during a power cut you wouldn't be recording any energy usage anyway!) Otherwise I can't think why the battery would be necessary.
Re: Alternative Power Supply
I guess it would be possible for emonTX.. we'd need to run everything at its lowest power consumption.. perhaps a supercapacitor would suffice, and also has the advantage of far greater charge/discharge cycles than a rechargeable battery :)
Re: Alternative Power Supply
Why is the supercapacitor/battery necessary at all? Can the device not be powered from a carefully chosen number of loops round the mains cable?
Re: Alternative Power Supply
U need at least a cap or a supercap to ensure a continuous power supply to ur electronics.
"raw wild AC" directly from the CT can not power ur electronics before being "adapted" to a more stable DC current
Re: Alternative Power Supply
Non-invasive current clamps produce a usable signal for measurement purposes, but very little energy is involved. Power transfer could presumably be increased by having multiple secondaries or multiple cores.
But if no current is flowing in the cable that's being measured, no power would be available by this means :(
Re: Alternative Power Supply
No energy consumption, no monitor?
since the ct output is proportional to the current flowing, if there is no load on the line, there will be no voltage to drive the emontx, Right?