coltsfoot
Newbie level 3
Hello. This is a first post from a complete novice about a first circuit. I have made a small board to reduce a DC voltage from a nominal 12v to a nominal 9v using a LM317 voltage regulator. Having made the circuit, with 13.5v going in, I am getting 7.3v coming out. This is without any load other than my meter.
I wonder if there is something about the resistor choice, other than their relative values, that is important. Not knowing that there was anything other than a ratio between the two
In addition to the 2 resistors, there are 2 Tant Capacitors (0.1uf and 1uf) across input and output.
I have since found sites indicating that R1 should not be less than 100Ohms -eg
LM317 Voltage Calculator - Electric Circuit
The product information gave no minimum value for R1.
Can anyone help me with this please?
thanks
Coltsfoot
I wonder if there is something about the resistor choice, other than their relative values, that is important. Not knowing that there was anything other than a ratio between the two
I went for 10ohm and 62ohm as this gave me the 6.2 (R2) to 1 (R1) ratio I needed.(from the formulaVOUT = 1.25 * ( 1 + R2/R1 )
)
In addition to the 2 resistors, there are 2 Tant Capacitors (0.1uf and 1uf) across input and output.
I have since found sites indicating that R1 should not be less than 100Ohms -eg
LM317 Voltage Calculator - Electric Circuit
The product information gave no minimum value for R1.
Can anyone help me with this please?
thanks
Coltsfoot