Re: Circuit description?

On Sun, 26 Mar 2006 15:22:42 +0100, "Gareth Edwards"
<gareth.edwards100@xxxxxxxxxxxxxx> wrote:

Could anyone give me any help with the following circuit?

http://www.piczs.com/is.php?i=25589&img=img004.jpg


Can anybody explain to me exactly how this circuit functions, what it does,
and why were the components chosen i.e. how were the resistor values
calculated etc.
Where it says "solar +ve", this is the positive pole of a small solar
panel.
The circuit works on 2 AA batteries in series (3 volts).
R1, R2, and R3 are all resistors.
The capacitor is a 101. 100pF ceramic disc type.
Two transistors are S8050 type.
Diode is a 1N5819.

I have made a mistake on the drawing, L1 and L2 are inductors, not resistors
as it states.
I think they should be labelled as 470 mH.

The circuit is taken from a solar powered lantern for the garden. It
charges up during the day, and the light comes on when it gets dark. The
light is supposed to last around 8 hours if it has been charged fully.

Thanks for any help.

Gareth
Thank you for YOUR help! I drew this circuit out some couple of years
ago, but couldn't see how it could work. But if you are correct about
the inductors then it all makes sense! (I had assumed they were
resistors from the marking and never checked them).

Basically it is an oscillator (as you will find if your hold a small
pocket bc radio near it). The inductors generate a higher emf (as in a
switched mode power supply in certain configurations), which supplies
a higher voltage for the led (2.5 volts is not enough from two
nicads). Some use only a single nicad (or two in parallel), but the
circuit can generate a high enough voltage (usually over 4 volts) -
depends on the inductors and caps. The diode rectifies the square wave
ac.
Anyway, that's my reading of it.

Best wishes

Eric Sears ZL2BMI.

.

Relevant Pages

  • Re: generalized Thevenin?
    ... Essentially I have a circuit where each "branch" looks identical(Actually ... passive elements characteristics. ... graph/solve the system for the voltages and currents? ... For two resistors, the voltage at the middle point depends on the ...
    (sci.electronics.design)
  • Re: transient analysis of linear system
    ... Anyway the circuit is shown above. ... voltage divider of the difference of Vx and Vy. ... The point of all this is to 'see' if the resistors change ... solving linear systems are not applicable (except for short times while the ...
    (sci.electronics.design)
  • Re: transient analysis of linear system
    ... Anyway the circuit is shown above. ... Clearly in steady state it's just a voltage divider of the difference of Vx and Vy. ... The point of all this is to 'see' if the resistors change through the "fog" caused the time varying sources. ... Looks like you have everything wrong, attempting to measuring a circuit parameter that nature is forcing to be constant, meaning you have to measure *current* to detect the resistor changes, the voltage measurements will barely move by ppm and be undiscernible from drift. ...
    (sci.electronics.design)
  • Re: transient analysis of linear system
    ... Anyway the circuit is shown above. ... voltage divider of the difference of Vx and Vy. ... the user but it must be the steady state result. ... The point of all this is to 'see' if the resistors change ...
    (sci.electronics.design)
  • Re: transient analysis of linear system
    ... First of all this is not homework it's just that linear systems and transient circuit analysis hasn't been in the job description for a while, ... I know all the values for caps and I can also measure *all* voltages. ... The point of all this is to 'see' if the resistors change through the "fog" caused the time varying sources. ...
    (sci.electronics.design)