Friday, October 10, 2014
LM317 variable power supply
Description:
A truly timeless circuit. LM317 is a versatile and highly efficient 1.2-37V voltage regulator that can provide up to 1.5A of current with a large heat sink. Its ideal for just about any application. This was my first workbench power supply and I still use it.
Since LM317 is protected against short-circuit, no fuse is necessary. Thanks to automatic thermal shutdown, it will turn off if heating excessively. All in all, a very powerful (and affordable!) package, indeed.
Although LM317 is capable of delivering up to 37V, the circuit pictured here is limited to 25V for the sake of safety and simplicity. Any higher output voltage would require additional components and a larger heat sink.
Make sure that the input voltage is at least a couple of Volts higher than the desired output. Its ok to use a trimmer if youre building a fixed-voltage supply.
Problems:
Follow all the safety precautions when working with mains voltage. Insulate all connections on the transformer.
Possible uses:
Variable workbench power supply, fixed-voltage supply... Just about any possible application when no more than 1.5A is necessary.
read more at: http://english.cxem.net/power/power8.php
Wednesday, September 3, 2014
Power Supply Variable 1 3V 12 2V 1A Circuit
In addition, the power supply circuit is also equipped with over-current protection or shield against belebih flow. Power supply circuit is very simple, but the quality is quite good, made her basiskan regulator IC LM723 is a pretty legendary.
Description:
R2 to set the output voltage. The maximum current is determined by R3, over-current protection circuit inside the LM723 to detect the voltage on R3, if it reaches 0.65 V, the voltage output will be off her. So the current through R3 can not exceed 0.65 / R3 although output short-circuit in his.
C3 and C4 are ceramic capacitors, as much as possible directly soldered to the PCB, this is because the LM723 is prone to oscillation that is not cool.
LM723 works with 9.5V input voltage to 40 V DC and the LM723 can generate its own current of 150mA when the output voltage is not more than 6-7V under input voltage.
Specifications:
Output (value estimated):
Vmin = (R4 + R5) / (R5 * 1.3)
Vmax = (7.15 / R5) * (R4 + R5)
Imax = 0.65/R3
Max. Power on R3: 0.42/R3
Min. DC Input Voltage (pin 12 to pin 7): Vmax + 5
Component List:
B1 40V/2.5A
C1 2200uF (3300uF even better)
C2 4.7uF
C3 100nF
C4 1NF
C5 330nF
C6 100uF
Green LED D1
D2 1N4003
F1 0.2A F
F2 2A M
IC1 LM723 (in a DIL14 plastic package)
R1 1k
R2 Pot. 5k
R3 0.56R/2W
R4 3.3k
R5 4.7k
S1 250V/1A
T1 2N3055 on a heatsink 5K / W
TR1 220V/17V/1.5