Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

use of a resistor to drive l.e.d. from 30 volts supply

Status
Not open for further replies.
rajaram04

rajaram04

Advanced Member level 3
Advanced Member level 3
Joined
Jun 17, 2012
Messages
871
Helped
6
Reputation
12
Reaction score
5
Trophy points
1,298
Location
earth
Activity points
7,687
Hello sir
i made a transformer less power supply to drive it from direct a.c. source so as to drive some l.e.d. lights for normal use & i measured the voltage as 30 volts with no load connected between the output terminals , now please tell me how to drive a single white or green l.e.d. from this supply ? what parameters of a resistor must be there ? , please give all the specifications to obtain a full light here .
thanks
 

depending on the current you want (or according to spec) you need a resistor of value

(30-3.5)/I for white or
(30-2.1)/i for green

Use I in Amps for R in Ohms

hope it helps
cheers
 
  • Like
Reactions: IanP

    I

    IanP

    Points: 2
    Helpful Answer Positive Rating
rajaram04 said:
Hello sir
i made a transformer less power supply to drive it from direct a.c. source so as to drive some l.e.d. lights for normal use & i measured the voltage as 30 volts with no load connected between the output terminals , now please tell me how to drive a single white or green l.e.d. from this supply ? what parameters of a resistor must be there ? , please give all the specifications to obtain a full light here .
thanks
Click to expand...
It will be safer for you if you presented here the whole circuit, as the no-load voltage of a transformer-less ps can be very misleading.
Compare your circuit with the attached one: it has Zener across the output that sets the level of the output oltage ...
:wink:
IanP

https://electroschematics.com/5678/capacitor-power-supply/
 

Attachments

  • Transformer-Less CAPACITOR-POWER-SUPPLY.png
    Transformer-Less CAPACITOR-POWER-SUPPLY.png
    5.8 KB · Views: 185

the idea of direct connection to mains is very bad, in some cases can be hazardous. Just wonder why all the electronics use transformers.

anyway, maybe you could use a variable regulator (lm317) and drive the leds without resistor, just drop voltage to 3v
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top