Electronics > Beginners
12v Battery Charger Circuit using LM317 (12v Power Supply)
queennikki1972:
Thinking about building this project.
https://circuitdigest.com/microcontroller-projects/12v-battery-charger-circuit-diagram-using-lm317 but I need someone to tell me if the circuit is incorrect and also decipher the BOM..
Specifically the recommended wattage for all resistors and (Diode- Nn007 (3)) Do they mean 1n4007 for example? They also mention a 0.05R - Shunt Resistor/wire but I dont see on the schematic.
I wont be using the Arduino nano or lcd
queennikki1972:
Nevermind on the diodes, i see that it should probably be 1.5 amp diodes
woodchips:
What a bizarre circuit!
Look in any application note for the 117 for a LA battery charger that is far more subtle. It uses a low value, 0.5 ohm or so. series resistor between the out terminal and the voltage divider going to the adjust pin. This automatically adjusts the charge current as the voltage rises, work out how!
queennikki1972:
found it! Very simple circuit instead of this one.
http://www.ti.com/lit/ds/symlink/lm117.pdf page 24
Zero999:
--- Quote from: queennikki1972 on April 30, 2019, 03:45:02 pm ---Thinking about building this project.
https://circuitdigest.com/microcontroller-projects/12v-battery-charger-circuit-diagram-using-lm317 but I need someone to tell me if the circuit is incorrect and also decipher the BOM..
Specifically the recommended wattage for all resistors and (Diode- Nn007 (3)) Do they mean 1n4007 for example? They also mention a 0.05R - Shunt Resistor/wire but I dont see on the schematic.
I wont be using the Arduino nano or lcd
--- End quote ---
Connecting an LM317 current limiter in series with a voltage regulator circuit, like that is a bad idea, because it requires a lot of voltage headroom to work. The LM317 voltage regulator circuit, needs an input voltage of about 3V more than the input. The current regulator circuit needs an additional 1.25V, as that voltage is dropped across the sense resistor: 4.25V. An LM317 voltage and current regulator in series, require an input voltage of around 7.25V more than the output voltage. Then the diode on the output will drop even more voltage.
A 12V transformer is much to low for this circuit. It needs an 18V transformer to stand any chance of working properly.
--- Quote from: queennikki1972 on April 30, 2019, 04:11:42 pm ---found it! Very simple circuit instead of this one.
http://www.ti.com/lit/ds/symlink/lm117.pdf page 24
--- End quote ---
Yes, that's a better idea. Figure 34, on page 26, is also a good idea, if sensing the current on the negative terminal of the battery, is acceptable.
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