switching voltage reg for 5v

[sherazi]

regards!

i am currently using 7805 regulator for 12v ac converted todc and then fed to 7805, i have a microocntroller avr Atmega8, and a uln, amax485 and atleast 3-4 leds that are constantly on .... hence the regulator gets too hot... i want to replace it by a swithing regulator... one option for me is this one .

can you plz suggest me a one that can easily be replaced for 7805, and that would work great...

 

[john blue]

Put a heatsink on the 7805. But, it shouldn't get too hot. Did you put resistor for the LED's?

 

[sherazi]

ya they were 470 ohms.. LEDs are bright..without the sink as i know it should heat up

we have (17-5)=12V and current if 80mA so P=12*80x10^-3=.96W
if this is converted to heat...it should get heated up...

80mA is a rough calculation...

---------- Post added at 07:50 ---------- Previous post was at 07:46 ----------

thermal resistance junction to air: 65 K/W
Assume ambient=30 °C its GULF [ME]

At 1 Watt: 30°C+65K=95 °C, that hurts
At 2 Watt: 30°C+2*65K=160°C , that's too much

 

[john blue]

**broken link removed**

 

[sherazi]

why i shouldnt use this one http://shop.tuxgraphics.org/snippets/R-78xx-0.5.pdf

 

[nandhu015]

regards!

i am currently using 7805 regulator for 12v ac converted todc and then fed to 7805, i have a microocntroller avr Atmega8, and a uln, amax485 and atleast 3-4 leds that are constantly on .... hence the regulator gets too hot... i want to replace it by a swithing regulator... one option for me is this one .

can you plz suggest me a one that can easily be replaced for 7805, and that would work great...

What is the overall current requirement?

it is better to go for a switching regulator if it is more than .5A

 

[sherazi]

which one would be better to use? the one i placed link of ? or any other?

 

[RCinFLA]

Adjustable step down switching voltage regulator

 

[Tahmid]

Hi,
I have used the ones from ST Microelectronics and found them to be very good. There is one L4976(1A) and L4971(1.5A), both of which are available in PDIP packages.
Hope this helps.
Tahmid.

 

[onlyAman]

lm2596/fs2096可能适合你,最大负载电流3A,效率80%。

MOD: Use English only..

 

[war4one]

i am currently using 7805 regulator for 12v ac converted to dc

You must insert diode bridge or single diode between AC source and 7805 regulator