Thursday, October 8, 2015

Different LED characteristics for 5mm LEDs


This chart shows the differences between different types of 5mm leds. These measurments are the average numbers for theses types of leds, but other companies led's characteristics may be different.
You may want to look at the manufacturer's specs before trying to use this for 5mm leds.

Simple automatic lead acid charger/maintainer using LM317



Automatic Lead acid charger
The circuit above is a simple circuit that can charge or just maintain a 12v lead acid battery. This circuit uses a Lm317 and the circuit can only supply up to maximum of 2 amps but with a big heatsink. To use the circuit you would connect the power side to a 14 to 18v power supply and the green led turns on. Then you would connect the 12v lead acid battery to the battery side and the red led turns on. Use and turn the 5k potentiometer, so that the output voltage matches 13.3v (which is a fully charged 12v battery).  When the battery charges the battery will take in a lot of current causing the transistor to switch on and light the led, but as it continues and gets charged up, the battery takes in less current, causing the transistor and led to turn off.
To increase the current capability to charge larger batteries, parallel another 2 or 3 Lm317 regulators.
 On the left shows the pinouts of the Lm317.

Disclaimer: This is just a DIY charging circuit for a lead acid battery, this circuit may not be that reliable,  and it can create a lot of heat from the Lm317 which is a fire risk. So do this at your own sake and i suggest buying a proper battery charger, this is just a cheap solution.

Solar buck converter using NE555 timer

Solar buck converter
The circuit above is a buck converter which can boost or buck(decrease the voltage). This circuit uses the Ne555 timer and is the same circuit as the pwm dimmer circuit but modified with a inductor, extra diode and a 7812 linear regulator. The inductor rating is a trial and error, i would est a 40 to 60 uH cored inductor. To use the circuit you would turn the potentiometer on the top left either left or right so that it either increases the voltage or decreases the voltage.
As the voltage decreases, the current output should be higher and as voltage increases, current output should increase. The input voltage of the circuit should be at least 13-30v as long as you have the 7812 regulator.On the left shows which the gate, drain and source of the n-channel mosfet diagram. Below shows the pinouts of a IRF540 n-channel mosfet.




Note: The output wattage will never exceed the input wattage.