Solar generation, Home Easy units, and Jeenode remote switching

6 replies [Last post]
Joined: 28 May 2013

This is my first post, apologies if this is in the wrong forum. Sorry this is a bit long winded but I felt I needed to give some background to the project.

We have a roof mounted solar array which can generate up to 1.48KWp. In the UK, power generated by domestic mains-tied PV systems are supported by a Feed-in Tariff payment per kWh . In addition there is an additional payment for electricity fed back into the grid. For small PV units the amount is not metered but assumed to be 50% of that  generated.  I am attempting to make a set-up which will enable this “surplus” to be used, rather than exported.

There are existing units which enable this to be achieved but these are expensive and most have to be wired into the mains supply.

I wanted a design which could be safely carried out by simply switching a Home Easy plug adapter (HE302S). I initially used a dedicated circuit and LDR, to monitor the mains supply LED. This pulses once every 1Wh used. However when there is more generated electricity  than electricity being used, the LED is continuously on.  The circuit detected this and then, via a relay, actuated a Home Easy magnetic switch (HE305). (This was modified by removing the reed-switch and extending the contacts to the output of the relay)   This sent the ON command to the plug unit, which switched on a low wattage (850W) kettle.

 It worked, but there were two problems. In the case when the generated power only just exceeded the amount being used, the additional load immediately exceeded the threshold, and the kettle would be switched off. This caused unwanted cycling. In addition the range of the Home Easy unit (433.98MHz) was variable and often failed to switch.

I decided that the Jeenode would provide a much more flexible solution and a better RF range.

My starting point was a sketch based on  With some modifications this is now working and can generate a value for the average power being used over a minute. A potentiometer is used to set a generation threshold above which the Home Easy plug needs to switch on.  This can be set with a sufficient margin to, in most cases, prevent cycling.

However, the next step, is to add an additional pulse monitor on the mains supply meter LED. In the event of an additional high load item (immersion heater, for example) being switched on this will immediately switch off the Home Easy plug, and switch it back on when the additional load does off.

Once working I am hoping that I will be able to send a simple ON/ OFF command to the Home Easy plug unit. As the frequencies are not compatible I still intend to use the Home Easy magnetic switch arrangement, but driven from a relay at the output of the remote Jeenode. This should overcome any range issues.


I am looking for a simple way of remotely actuating this relay using the RF12 protocol, but have not discovered any information how this might be achieved. Any help would be most useful at this time.

Glasgow, United Kingdom
Joined: 26 Oct 2009
Centralised control is king

Hi Keith,

Welcome to the HAH forums. 

Interesting application. 'Dumping' power to a kettle isn't something that I've heard of before (what happens once the kettle is boiling?). I have heard of folks running immersion heaters to heat a much larger tank.

Your choice of the Jeenode over a standard 'fire and forget' 433MHz is good. Being bi-directional, you can have the Jeenode acknowledge any command and arrange for a retry if necessary.

Relay control via Jeenodes is covered here

Which kinda brings me to why you might want a HAH unit. With xAP as the message protocol behind the HAH and the HAH Plugboard scripting engine in place, you have a very capable (and low power) control platform. You can easily introduce hysteresis to controlled devices and take decisions based on time of day/actual temperatures at remote locations/actual power use by individual appliances (via Current Cost IAMs) in a structured way. Remote control via internet and feeding historical info to a service such as xively also becomes possible.

There are other solar PV users here, so you might get feedback from them.


United Kingdom
Joined: 31 Mar 2011
My thoughts

Hi Felix, welcome to the forum.

if I have read your post correctly, then you are asking how to control a relay at a remote jeenode via rf12. Are you transmitting from jeenode also?. If so, I suggest you scour through the HAH source code (links in the left of the forum) to find HAHCentral and outputnode sketches in the arduino section. These will show how the HAH sends data to control relays on remote jenodes via a central jenode attached to the HAH via serial. 

On your project in general though, I can't help but think you are putting a lot of effort into building a bespoke one job system. This being the HAH forum I suppose its obvious we would push the system but I really do think that would be a more flexible system for you with less work to do yourself.

my thoughts on how I'd approach your problem:

current cost power and pulse reading via enviR unit linked to  HAH.

lua script to monitor usage and make decisions on switching.

rf control of socket via HaH 433rf board with native control.

whilst a bit daunting and maybe more expensive at first, this then opens up much more possibilites in the future as we all on here have found out. I use mine for tasks I never dreamed of when all I originally wanted to do was turn lights on and off.

Anyhow, good luck with the project, whichever route you go down




edit: just noticed that Derek beat me to it! And more eloquently too!

Ayr, United Kingdom
Joined: 25 Sep 2011
There are quite a few people

There are quite a few people doing this sort of thing. It looks like you have a hardware addition to your system which is very much like the one used by Dean as shown here:

He uses a plugboard script which allows the HAH to do pretty well what you have in mind. As far as I know it works pretty well. It uses a time delay to stop the repeated switching of a device. If you are thinking of using the HAH for the same purpose then the script should be fairly easy to modify. Just let us know if you would like a copy.


There is also another system discussed here:

although I'm not sure how effective this is.

Let us know how you get on.



Joined: 28 May 2013
Thanks for your quick and useful replies

Many thanks for all your very useful comments. I think I can now see the wayforward to realise the design. However, your comments on the HAH unit has certainly stimulated my interest. I shall be looking into this as the more versatile set-up in the near future.


best Regards



United Kingdom
Joined: 11 Jan 2011
I do

Yes i use HAH for many things and did develop a system to heat my immersion in two levels.

phase 1 fired a modified home easy plug to switch immersion on with a large diode in series so it consumed 800W

phase 2 fired a seperate one which "shorted out the diode" and effectively fed the immersion with 1500W

the conditions were that 1 i was feeding the grid and 2 generating over 1.2KW and 2.2KW repectively.

there was anti bounce built in as well. Oh and i have 2 heaters in my tank both rated at 3KW which i wired in series.

it did work very well, then i got an immersun unit on trial and that now does it all very very well.

the immersun is certainly worth the investment if the house is empty during the day. and estiamated payback is 2-3 years. especially now they are only £349inc vat

you do need 2 things an immersion heater, and this needs to be fed independantly from a circuit breaker off your distribution board.

any electrician with correct regulations can fit one and it should take them (if they are any good) under an hour.

I fitted mine and got an electrician friend to come and sign off (cost me a drink £20), took me 30Minutes from start to finish.


Bristol, United Kingdom
Joined: 31 Mar 2012
I'm using EJ's I-Gen which

I'm using EJ's I-Gen which pulses 100% of any excess power it constantly monitors home power usage and solar generation and pushes the excess to the immersion, works fantastically well starts pushing about 300 watts (as said when available) right up to 3KW...

If you are interested take a look at my to see live data. 

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