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Un-Available 5V DC power source

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KhaledOsmani

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How to have 5V DC source?
Regardless of using this voltage regulator: 7805 and regardless of connecting bunch of 1.2V in series.

Thanks.
 

I=0.1A using only the keypad and the LCD. The Circuit will later involves LDR, lm35, soil moisture sensor, 4 relays of 12V, (used as open relay switch) to accommodate 220V actuators like fan, light bulb, valve, etc...
 

Do you have mains power available? If so use a wallwart 5VDC, some hundred mA. You will need an extra 12V source then. Or you could get a 12V wallwart and use a DC-DC converter from 12 to 5V, if you don't want to use a 7805.
 

I have a wallwart of 12V. But its output current is 500mA which is too big for my circuit.
What type of DC - DC converter?
 

Ok. I see.
Even thought, when the output is 6V, and want to convert it using the voltage regulator, (according to its datasheet) to 5V, When I test the output with a voltmeter, it shows that the output is 5.6V.
This +0.6V could damage the LCD.
Why the regulation isn't 100% efficient?
 

If you have a 12V wallwart, use a 7805 to get 5V, that is the easiest way to go. If you only use 100mA, there is little loss in the 7805, but you should still use a small heatsink anyway.

There are several small DC-DC switch mode regulators that can be used, but you need more components outside the chip. In addition, these regulators are normally only available in SMD packages. This mean they can be difficult to solder by hand, if you are a starter in electronics.
 

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