general newbie hello, and request for guidance :)

 Hi All, 

followed various threads for a little while now (on and off for a few months.)

like most of us i have PV and until recently didn't really worry about the excess as i had a nicely spining backwards meter. but when my supplier finally puled there finger out and sent me through all the docs i caved-in and informed them. so of course i now have a nice 'microgen compatible' meter. lucky for me its still a spinning disc but will now only spin back 1 rev before hitting a back stop.

anyway had looked at various 'expensive' options like the emma, Mr Rudge's 'relay'  and decided i could do better. Bought myself a Arduino Uno to play with, a chinese 0-crossing SSR. so after messing around with LEDs and filament lamps i have put the SSR into the Immersion circuit and at the moment while the sun shines it ticks over nicely. Though of course I have to tweak it from time to time.

questions here...relate to is there any problem with using the SSR as is.. , as i see others have used much more expensive devices...and also separate opto-isolators and triacs... to me the SSR (isolation and triac in a box) seemed to  be a convenient compromise... or have i missed a serious 'gotcha'  ?

The emon TX, Base and GLCD seem like great tools for capturing all that information, so you can make sensible decisions about what to do with all that excess...

But... I may be missing the point here... there doesn't seem to be a emon unit for 'control'

Or is that just it.. either of the emon Base or TX could be set to have an output to control my SSR (or whatever.)
are these option built in to the available firmwares or is another box needed so it has enough cpu capacity for bits of processing per halfcycle etc etc..

another question i had while looking into RF comms with arduino was, who easy/hard is it to interact with.
if say i wanted to report excess watts via RF to my hypothetical emon 'control' unit. (or units as I  have a couple of things to control.. and neither is particularly close to the monitoring location.)

I looked at panStamp devices as their stack for RF comms looked interesting..and also the Jeenodes  which seem like nice units. I guess the jeenodes would be most likely to be able to talk to the emon units as they use similar RF units...

And finally, i see progress with the SMT version of the TX is progressing... does/will the improved accuracy of the CT circuit make a big difference (or other new features) should i wait for them to be available :)  or  take the plunge and buy a full kit to build now.

so anyway thats more than enough for now...

uh..nice to meet you all...keep up the good work.






richmc's picture

Re: general newbie hello, and request for guidance :)

Seriously, look at the MK2 PV controler with triac thread. It is the holy grail!

It will divert excess solar to the immertion heater till your tank of water is as hot as you want it, this will get you going at minimum cost, it only needs a triac (with optocouple) to switch the heater and whilst in use uses all available excess without importing from the grid. The spcific optocouple is a zero crossing device, if your SSR is a zero crosser it could work although the components specified are as cheep as chips (see my post on costing).

Sexy bits like an LCD display can be added later, but if you want to start saving energy (and cash) stright away have a look.

Robert Wall's picture

Re: general newbie hello, and request for guidance :)

Hello, Newbie!

But... I may be missing the point here... there doesn't seem to be a emon unit for 'control'

I aim to be doing that very soon. There's no reason in principle why an emonTx (less the RF in my case) can't be used as the controller, and when the parts arrive I'll be able to tell you whether it works! The only change from Calypso-rae's circuit is the current-limiting resistor in the opto LED drive needs to be reduced to allow enough current with the lower 3.3 V supply.

I did some quick tests with an emon with the Tx and two c.t's and decided the processor load to report infeed and generated power, VA, current, voltage and power factor as well as controlling was too much for one processor, so that (and a 2ft thick stone wall in the rf path) made me split the system so I'll be installing a monitor system and a totally separate control system.

The beauty of Calypso_rae's controller is it works on the negative feedback principle, so rather than measuring consumption and generation, it attempts to control to achieve zero nett infeed energy.

richd's picture

Re: general newbie hello, and request for guidance :)

 yep been following most of it...the early parts .. and i just looked today and found its grown alot while i have been away on hols..

apart from the energy buckets :)  and the eye diagrams which kinda lost me for a bit seems all straight fwd.

your install looks nice and tidy, I split my Immersion wiring out of the switched isolator and mounted the SSR and heatsync on the wallboard next to it.  the SSR has a simple finger shield.. but it isn't enclosed atm (though it is out of reach) bit naughty i know, i will put a box round it soon.

I have a choice in the monitoring as well, as when i had my meter changed i got them to put a DP isolator on the tails..
so I can work on the tails and the CU safely. so my plan was to split out the feed to the CU and the feed from the inverter and put a CT on each.
It seems like i might not need to do that now with the setup you  have all been working with using the ac/ac transformer, assuming i can find a suitable one.

i see you published your PCB designs and a kit list too. excellent !

can you or anyone recommend a suitable solid core CT...
i figure as i am able to work with the main tails... i might as well put the best sensor I can on them.



richd's picture

Re: general newbie hello, and request for guidance :)

Thanks RW for your comments too.

I also have a RF pathway problem as i live on a hill, my house is partly built into a slope, so there is a very thick wall and a fair amount of dirt to get through. to get data from the CU to the rest of the house i may almost need another new product,  emon RF 'relay'

I hadn't appreciated the emon was 3.3v based,  though that might be enough to drive my SSR will have to check.
the number of atmel/arduino type boards is staggering, and i've looked at so many..i get confused about which ones do what now.
so far my only experience is with the 'Uno' and thats 5v i think. (but has a 3.3v regulator too ?)

Seems like the lower V setups are clocked slower from what i've read, but hey i'm a newbie arent i :)

Calypso_rae's solution does indeed appear... well, elegant, i guess.




markcarter10's picture

Re: general newbie hello, and request for guidance :)

Have a look here


lots of discussion going on

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