Very low powered light help

What voltage do you need and what current?

The LEDs mentioned wouldn't normally be classed as high voltage....

Simple Solar Circuits | Evil Mad Scientist Laboratories Has some ideas if light is present.

Clem

PS www.cypress.com/documentation/reference-designs/mppt-based-solar-charge-controller-reference-design ideas again?

Thanks for the info! Below is a slightly more detailed explanation for this project.

I need to make a boost converter which outputs high voltage (relative to input voltage, of course) but with low amperes.

This circuit is commonly known as "Joule Thief".

I need to somehow make it shut off during daytime and work under batteries, which may or may not be rechargeable. (The circuit I am trying to build will have no support for charging, though)

Agendas:

• Make a high-V low-I boost converter, with minimal parts available basically anywhere
• Make the circuit shut off during daytime and turn on during night
• No microcontrollers allowed (due to its cost and possible hiccups during programming)

It's okay, sans PIC microcontroller.

The battery can be turned off during daylight with a cadmium sulfide sensor, resistor and a PFET.

The LED can be driven from low voltage with an inductive relaxation oscillator, or any oscillator with an inductive flyback output. The circuit plus FET switch takes 2 or 3 transistors.

The biggest problem is the very low minimum working voltage - almost nothing with general purpose components can work efficiently with 0.7V supply.

At low currents Alkaline batteries provide very little power once the voltage has dropped below 0.9 or even 1.0 volts so using two batteries gives you a lot more scope.

My favorite approach (based on not  a lot of time thinking about it)  would by a 6 pin PIC processor (works down to 2V), 2 x MOSFET, a diode, an inductor and some capacitors  - if that kid of parts list is acceptable I can go into more detail.

MK

Hi

There are many LED ic driver, for different currents, fixed or adjustable, with different topologies buck, boost... depending on input voltage, and how you connect LEDs in the output (single LEDs, or a string of several LEDs). If your power supply has lower voltage than the LEDs in the output, then chose a boost topology. Also, very important to know the current you want through the LED, as D_Hersey suggest, LED are typcally controlled by current.

Hope that helps,

LEDs are typically excited with currents rather than potentials

The post has been updated as it did not convey what I intended. Sorry for the confusion!

p.s. The voltages and specs can be changed to minimum possible spec. Maybe I can make them work too.

You have an unclear (to me anyway) goal, and you've already specified a few tight technical requirements and restrictions.

This makes it hard to suggest any off-the-shelf design that will immediately suit all your requirements and restrictions, hence why people are suggesting you read around the subject of efficient LED lighting circuits, and low voltage lighting circuits.

Generally if you have tightly defined restrictions in some areas (e.g. that specific voltage range) then you're going to need to design and experiment yourself, but you could use some existing web resources for ideas (even if it helps eliminate some ideas or helps you relax some of the tighter restrictions).

By the way, no such thing as a generic 3V LED of almost any color, some colors (including some that you suggested) need a higher voltage than 3V. That difference matters significantly for voltage multiplying/boost type circuits if you're working with such low supply voltages as you suggest.