Light Activation Switch

Yut_Man

I have been looking around to see if there is a way to use certain electric items when my solar panels are working at a descent level. Are there such things as dawn to dusk mains switches about?. All the ones I have seen come on at night and go of in the day. I want it the other way around. Im sure there must be a clever way I can use the switch the other way around if not. ie relays etc.

thenudeone

You can easily buy stand-alone dusk-to-dawn switches (eg B&Q) but you would need to use a mains-rated relay if you wanted to use it in reverse.
A normal switch would only switch on (or off in this case) once it gets quite dark. You want it to switch when it gets overcast or cloudy, so you'd need to have some means of having an adjustable shade so that the switch itself was darker than daylight.

If you can get one working safely and cheaply, there would be plenty of interest!

energysavingexp

hi ive been thinking about this for a week or so.

light sensor are easy to build or buy not expensive
need a large mains realy also.
the main thing is to get it to switch on when solar is producing say more than 1Kw exporting and use the switch to kick in then. i was thinking of running say an electric heater or some thing like that.
it would not be any good to run things like washing machines
as it would be switching on and off all the time when a cloud came over.

what was you thinking of running?

i have 2 monitors in the living room, 1 shows solar pv output live in watts, and the other one shows expot/inport to and from the grid, when the l.e.d light is on it shows export wattage to grid, when l.e.d is off it shows inport from the grid in watts

Yut_Man

Where obviously thinking along the same lines. Small electric oil heater maybe if I get the power and its predictable enough. Failing this a small charger to top up a battery I use for my shed lights.

energysavingexp

Yut_Man wrote: »

Where obviously thinking along the same lines. Small electric oil heater maybe if I get the power and its predictable enough. Failing this a small charger to top up a battery I use for my shed lights.

i might have a go at making one later today

at the moment when i am exporting more than 1 kw

i turn on one of the water tank heaters.

the tank has 6 x 1kw heaters so i just turn 1 on if im exporting 2kw then i turn 2 on
the only trouble is im up and down all the time turning them on and off.

so yes i think i will make one today

off 2 maplin to buy the parts now.

light switch cost about £6 plus realy cost.

ps.
i also charge 2X 80amp 12v leasure batterys up during the day and run an 1kw inverter on them at night this runs my 50" tv and vcr for 3 full hrs each night :beer:
im in all day and my daily kw inport from the grid is 3kw

rogerblack

Yut_Man wrote: »

I have been looking around to see if there is a way to use certain electric items when my solar panels are working at a descent level.

You could use a very simple solution.
A tiny solar panel - around a watt or so, and a big relay.
This will have the disadvantage it will switch with every little cloud, so will only be suitable for some loads. (convector heaters, immersion heaters, ...)

grahamc2003

thenudeone wrote: »

You can easily buy stand-alone dusk-to-dawn switches (eg B&Q) but you would need to use a mains-rated relay if you wanted to use it in reverse.
!

A simple bit of Boolean maths solves the problem. A dusktodawn switch is basically a NOT switch. While two wrongs don't make a right, two NOTs do make an equal.

So you get two dusktodawn switches, the first to operate a bulb (on at night, off in the day), and a second sensing the bulb. The output of the second one would be on in daylight and off at night, or dawntodusk.

Not sure this is the most elegant or efficient solution though.

Yut_Man

some interesting ideas. Ive found pet shops sell something called a sun and moon switch for reptiles. only upto 600w though.

energysavingexp

just finished building a light operated switch that comes on in bright light and goes off in cloud.

rogerblack's idea is a good one just install a delayswitch in with it so its not on and off at evey cloud say delay of 2 mins

ps: it cost £5.99 to build light switch

energysavingexp

light operated switch been working well today, lots of cloud and sun. heter been switching on and off all day so its been making the most of my what would have been exported leccy

raider

I was looking into this idea when I had my SolarPV fitted. One solution I came up with was to use an x10 automation plug in module, connected to a 850w storage heater. Then using a program called automate on a running pc, grab the current solar output from sunny explorer. If it was over 1kw, turn the x10 module controlling the storage heater on, then re-checking the output maybe every 10 seconds or so.

All worked out a little costly for the amount of money saved, so didn’t pursue it further.