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I mean the backlighting. If I connect the backlight to LM7805, the regulator heats up even in the presence of a big heat sink. Can anyone help me with a solution to remedy the situation?
You should not be connecting the 7805 directly to the backlight which is typically rated at 4.2v maximum.
Best to use a fixed or variable resistor between the 7805 and backlight, mine is a 2k trimmer and is measuring 400 ohm to give a good brightness to the backlight though it may be a bit different on your brand of lcd , so start of with say 470 ohm.
Current from the 12v rail feeding the 7805 micro and lcd / backlight just 30 ma
Also would not use the transformer like your diagram, 24vac will just produce too much of a voltage drop and heat across the 7805.
Just using one secondary would be better.
To answer your comment about 48 v into a 7805, check its datasheet, the maximum input voltage is 35v , thats why it was over heating
According to datasheet, at 5V power supply current is typical 1mA and 3mA maximum. There is no backlight data because this LCD dont have background light.
Also would not use the transformer like your diagram, 24vac will just produce too much of a voltage drop and heat across the 7805.
Just using one secondary would be better.
To answer your comment about 48 v into a 7805, check its datasheet, the maximum input voltage is 35v , thats why it was over heating
Please what can I do in the case of 48V to stop the 7805 from over heating?
I am tapping my input from four 12V batteries which are in series and is already in use by an inverter. should I use a resistor so that there will be a drop across the resistor?
Please what can I do in the case of 48V to stop the 7805 from over heating?
I am tapping my input from four 12V batteries which are in series and is already in use by an inverter. should I use a resistor so that there will be a drop across the resistor?
Please what can I do in the case of 48V to stop the 7805 from over heating?
I am tapping my input from four 12V batteries which are in series and is already in use by an inverter. should I use a resistor so that there will be a drop across the resistor?
As Tpetar says you could use those very high voltage regulators, but I bet they will not be available where you are, they are not that common here.
You could make a transistor series pass regulator but thats a lot more complex.
A dropper resistor can really only be used if your load remains constant.
Is it just the backlight that you are trying to power by the battery or a full micro circuit whatever that is ? does it use relays or other higher current devices ?
You say there are 4 by 12v batteries in your invertor , surely you can connect another wire to the first or last battery in the chain so you can get a 12v output ?
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