Remote Living > Lighting

Dusk To Dawn LED light Control with Solar PV

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OperaHouse:
A simple dusk to dawn controller for a LED that operates off solar panel voltage with batteries.
This circuit uses a TL431 to sense panel voltage. A voltage divider feeds the REF pin with about 2.5V.
When that drops indicating sunset, the pull up resistor feds voltage to the FET gate. Many FET will turn
on with 3-4V on the gate and turn off below 2V.  The lowest saturation voltage for a TL431 is about
1.8V.  The voltage drop of two diodes give a low off gate voltage. For gates with higher on voltage,
the diodes can be eliminated. Standby current is very low at less than 1ma.  Ideal for small panel
and battery systems where getting as much charge current on cloudy days is important. A pot may be
used in place of the resistor voltage divider sensing panel voltage. A minimum resistance of 22K
must be used from the positive panel to the pot. The REF pin acts like a zener and currents over 1ma
can destroy the TL431. Due to limited gate drive voltage, current should be limited to 1A. A TP4056
should be used for lithium batteries, two diodes must be removed due to lower battery voltage.  IRF540 is only
an example of suitable FET, almost any will work.

Bruce S:
This looks like it'll be a good use for the little 12V 1.5W VW solar panels the dealers used to give away, unless the new car owner knew to ask for them.

I have some solar powered string lights this may be perfect for

Thanks!

ontfarmer:
What would you recommend for a switch for my wind turbine?  I have voltage control switches now that got from solar converters which have now closed there doors.  These switches are adjustable
and have a three second delay.  The turbine is three phase wound for 120 volt per phase.  The switches are set to progressively turn on restive heaters.

kitestrings:
ontf,

I was disappointed to learn that Solar Converters closed as well.  We use several of their converters.  Good quality & reasonable prices; this leaves a void.

There are, however several voltage control relays/controls around.  We've been using an Omron voltage sensing relay for high limit on our turbine.  The model we have has been discontinued, but there must be a model that supersedes ours (K8AB-VS).  I would look at Allied Electronics, Mouser, Digi-key or Newark.  You might also find something on one of the alternative energy providers like Backwoods Solar, Kansas Wind Power or AltE Store.

I know that some of the Solar Converters stock is still around - AltE and John Drake (aka Solar Seller) are couple places I've noted.  Good luck.

~ks

ontfarmer:

Kitestrings

Thanks for replying.  I will check those suppliers to see what is available.   

The arduino uno   I think could be used to  read the voltage and then sent to a relay or PWM.   Three
pins would be needed.  Don't think  I can do this on my own yet.
My education was obtained at a one room school house  ( eight grades )  Have learned a lot since then  and help  I get from you guys is greatly appreciated.

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