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#Post#: 5892--------------------------------------------------
Emergency Light
By: nessprojects Date: March 31, 2015, 5:09 pm
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I thought i would share this simple circuit that i have used in
the past. When powered up from the mains transformer it will
charge the NiCd batteries and the led lamp will be off.....upon
a mains failure the white led will light until the power is
restored.
Maybe this could be linked to the LJL lights in some way as the
voltage could be increased with a few changes to the circuit.
#Post#: 5893--------------------------------------------------
Re: Emergency Light
By: lynx wind Date: April 1, 2015, 9:33 am
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This is really helpful. I plan to install remote LED spot
lighting run off a solar panel and LJL for our neighborhood
welcome sign. There is no power available at the remote
location. It would be great if the lights would come on at
night off in the morning.
#Post#: 5895--------------------------------------------------
Re: Emergency Light
By: barbados Date: April 1, 2015, 2:28 pm
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Guys,
This sounds like a good idea, the light from the LJL is quite
substantial, for a remote location or area it could make a big
difference.
Best
Andre
#Post#: 5896--------------------------------------------------
Re: Emergency Light
By: nessprojects Date: April 1, 2015, 4:38 pm
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@lynx
I think if you are using solar and battery's and wanting to
operate as a Dusk to Dawn sensor then you may be better of with
the `Solar Light/Charger` that I posted in the middle of last
year.....With this Emergency light circuit as soon as the
voltage drops below the battery voltage then the led would light
so even on a dull day you may be using battery power
unnecessarily.....just a thought.
Just shout if you wish me to try and develop a circuit for your
application (I would try my best for you).
#Post#: 5897--------------------------------------------------
Re: Emergency Light
By: barbados Date: April 2, 2015, 12:29 pm
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@Ness,
Is it possible that you could give a short brief on exactly how
this circuit (Solar Light/Charger) works electronically?
Thanks
Andre
#Post#: 5900--------------------------------------------------
Re: Emergency Light
By: nessprojects Date: April 2, 2015, 3:53 pm
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@Barbados
I am a little confused as to which circuit you are referring to.
In the electronics related section there is another circuit
entitled `Solar Light/Charger`.
Please let me know which one you would like info on and I will
give a circuit description in the relevant topic for you.
#Post#: 5901--------------------------------------------------
Re: Emergency Light
By: barbados Date: April 2, 2015, 4:04 pm
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@Ness,
These are the circuits i mean.
Regards
Andre
#Post#: 5902--------------------------------------------------
Re: Emergency Light
By: nessprojects Date: April 2, 2015, 6:24 pm
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[quote]Is it possible that you could give a short brief on
exactly how this circuit (Solar Light/Charger) works
electronically?[/quote]
Re:- Solar Light/Charger
R1 and R3 are just a potential divider to limit the current flow
from overloading the solar cell and to bias Q1 (Keep it
suspended between the solar voltage and 0v).
During DARKNESS the solar is supplying no voltage so the base of
Q1 is at 0v hence Q1 will be switched off.....12v Battery
voltage cannot get past D1..... it will flow through R2 but
cannot get through Q1 so it holds the gate of the mosfet at 12v
hence switching the mosfet hard on and lighting the lamp from
the battery.
During DAYLIGHT the base of Q1 will now receive some voltage
through R1 (about 0.7v) but only low current due to the
potential divider hence turning Q1 on which in turn pulls the
gate of the mosfet down to 0v and thus turning the mosfet off
and no lamp will be lit.
Hope this helps you understand the circuit a little.
#Post#: 5903--------------------------------------------------
Re: Emergency Light
By: barbados Date: April 3, 2015, 5:11 am
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@Ness,
Asking your indulgence for a bit here.
I am trying to understand the calculation of the .7V at Q1
if i assume a charging voltage of 12.6V from the panel, i make
the voltage across R1 to be V1=1.145 AND R2 to be V2=11.45.
Are my calculations correct but i am not assuming component
voltage losses?
Let me know .
Thanks
Andre
#Post#: 5905--------------------------------------------------
Re: Emergency Light
By: nessprojects Date: April 3, 2015, 1:26 pm
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@Barbados
If you were to remove the link to the base of Q1 then your
calculations are spot on for R1 and R3 but because it is coupled
to the transistor base there is a current flowing from the base
to the emitter of Q1 (around 1.25ma)......Q1 base will only need
about 0.7v to turn fully on due to the emitter tied to the 0v.
Ohms law are V/IxR so 12.6v/10000(R1)=0.00126A or 1.26ma flowing
from solar positive through R1 then through Q1 to ground.
Hope this has helped you out a little.
Ps...I have just checked my circuit that has been running for
some time now and found that I don't have R3 on my circuit.
SORRY if this has caused any confusion but it would still work
with or without R3.
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