High quality, 3A adjustable voltage regulator. Using LM317 and 2N3055 so easy and cheap. Adjust voltage in steps 3V, 6V, 9V, 12V. And In fine, 1.25V to 20V. 4 Lead Acid Battery charger circuits See 4 LM317 Lead-acid battery charger circuits for 6V, 12V, and 24V battery. With automatic charging and full charged Indicator using TL431. The LM317 datasheet specifies that is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A 12V Solar Inverter Battery Charger D Mohankumar. Voltage was 12.13v across the Power, 9.20v across the LED, and 2.91 across the LM317v (0.95 over the resistor). All the numbers looked fine. Here's where it got tricky. Knowing the LED was rated for 12v, and the drop over the LM317 was 3v, I dug up a 15.2v 1.2A Power adapter, and plugged that in instead.
- In this project, we are going to design a simple LED dimmer circuit using the LM317T Regulator IC. LM317 is a three-terminal voltage regulator IC, with a high output current value of 1.5A. The LM317 IC has many features such as current limiting, thermal protection, and safe operating area protection.
- Sep 08, 2020 High quality, 3A adjustable voltage regulator. Using LM317 and 2N3055 so easy and cheap. Adjust voltage in steps 3V, 6V, 9V, 12V. And In fine, 1.25V to 20V. 4 Lead Acid Battery charger circuits See 4 LM317 Lead-acid battery charger circuits for 6V, 12V, and 24V battery. With automatic charging and full charged Indicator using TL431.
- Related:
In the above links I've explored using a constant current source (CCS) and basic theory. Here I'll concentrate on the use of a constant current source for lighting light emitting diodes or LEDs. Understanding series circuits and voltage drops will help with this subject.
Briefly in a series circuit the current through all series components is the same, while the sum of the voltage drops across each series component will add back to the source voltage.
In Fig. 1 we use a LM317 in its constant current mode. The value of R3 divided into 1.25 volts will determine load current through each LED in the string. In this case current is 1.25 / 4.7 =~ 266mA. Each LED has a slightly differing voltage drop which is normal and why we want to use a CCS. The total voltage drop across the 3 LEDs equals 12.2 volts while the drop across Us and R3 is 6.8 volts. They add back to equal the 19 volt power source.
Note that total voltage drops are limited to the power supply voltage and we should maintain drop across U3 and R3 of three volts leaving a drop for whatever load of 16V in this case. Drop more than 16V and the CCS will not function.
In Fig. 2 I've removed one LED and the associated voltage drop, but the drop across the other three LEDs remains the same. That missing voltage drop adds to the voltage drop across U3 and R3.
Fig. 3
Lm317 Variable Voltage Regulator
In Fig. 3 I've changed Vin to 24V and has no effect on the LED current, which is still set by R3 at 266mA. In all three cases above the voltage drops across U3 and R3 become useless heat.
The most efficient way energy wise is to use a switching voltage regulator to reduce Vin to 3-5 volts above the load voltage required.
- Computers Electronics for Normal People New Web Site
- My Homepage Off Site
- Quick navigation of this website:
Lm317 Laser Circuit Diagram
Web site Copyright Lewis Loflin, All rights reserved.
If using this material on another site, please provide a link back to my site.