The LM317T is associate adjustable 3-terminal positive transformer capable of provision totally different DC voltage outputs apart from the fastened voltage power offer of +5 or +12 volts or as a variable output voltage from a couple of volts up to some most worth all with currents of concerning one.5 amperes.
With the help of an atiny low little bit of extra electronic equipment supplementary to the output of the PSU, we are able to have a bench power offer capable of a variety of fastened or variable voltages either positive or negative in nature. actually, this can be a lot of straightforward than you will assume because the electrical device, rectification, and smoothing have already been done by the PSU beforehand all we want to try and do is connect our extra circuit to the +12 V yellow wire output. however, first, let us think about a hard and fast voltage output.
Voltage Regulator Circuit
The voltage across the feedback electrical device R1 could be a constant one. The 25V reference voltage, Vref created between the “output” and “adjustment” terminal. The adjustment terminal current could be a constant current of 100uA. Since the reference voltage across electrical device R1 is constant, a continuing current I will be able to flow through the opposite electrical device R2, leading to associate output voltage of:
Ratio of Resistances R1 to R2
| R2 Value |
Resistor R1 Value | ||||||||
| 150 | 180 | 220 | 240 | 270 | 330 | 370 | 390 | 470 | |
| 100 | 2.08 | 1.94 | 1.82 | 1.77 | 1.71 | 1.63 | 1.59 | 1.57 | 1.52 |
| 120 | 2.25 | 2.08 | 1.93 | 1.88 | 1.81 | 1.70 | 1.66 | 1.63 | 1.57 |
| 150 | 2.50 | 2.29 | 2.10 | 2.03 | 1.94 | 1.82 | 1.76 | 1.73 | 1.65 |
| 180 | 2.75 | 2.50 | 2.27 | 2.19 | 2.08 | 1.93 | 1.86 | 1.83 | 1.73 |
| 220 | 3.08 | 2.78 | 2.50 | 2.40 | 2.27 | 2.08 | 1.99 | 1.96 | 1.84 |
| 240 | 3.25 | 2.92 | 2.61 | 2.50 | 2.36 | 2.16 | 2.06 | 2.02 | 1.89 |
| 270 | 3.50 | 3.13 | 2.78 | 2.66 | 2.50 | 2.27 | 2.16 | 2.12 | 1.97 |
| 330 | 4.00 | 3.54 | 3.13 | 2.97 | 2.78 | 2.50 | 2.36 | 2.31 | 2.13 |
| 370 | 4.33 | 3.82 | 3.35 | 3.18 | 2.96 | 2.65 | 2.50 | 2.44 | 2.23 |
| 390 | 4.50 | 3.96 | 3.47 | 3.28 | 3.06 | 2.73 | 2.57 | 2.50 | 2.29 |
| 470 | 5.17 | 4.51 | 3.92 | 3.70 | 3.43 | 3.03 | 2.84 | 2.76 | 2.50 |
| 560 | 5.92 | 5.14 | 4.43 | 4.17 | 3.84 | 3.37 | 3.14 | 3.04 | 2.74 |
| 680 | 6.92 | 5.97 | 5.11 | 4.79 | 4.40 | 3.83 | 3.55 | 3.43 | 3.06 |
| 820 | 8.08 | 6.94 | 5.91 | 5.52 | 5.05 | 4.36 | 4.02 | 3.88 | 3.43 |
| 1000 | 9.58 | 8.19 | 6.93 | 6.46 | 5.88 | 5.04 | 4.63 | 4.46 | 3.91 |
| 1200 | 11.25 | 9.58 | 8.07 | 7.50 | 6.81 | 5.80 | 5.30 | 5.10 | 4.44 |
| 1500 | 13.75 | 11.67 | 9.77 | 9.06 | 8.19 | 6.93 | 6.32 | 6.06 | 5.24 |