EK031 Linear Voltage Regulator LM317
Part.no: 41024621
EK031 is a linear voltage regulator with a rectifier, allowing it to be powered by either AC from a transformer or DC from an unregulated or regulated power supply.
The output voltage can be adjusted using the included trim potentiometer (VR1). The board also has provisions for a standard 16mm panel-mounted potentiometer to be installed in place of the trim potentiometer.
The circuit is built around the well-known LM317 regulator and can operate with input voltages from approximately 4V to 40V. For optimal regulator performance, the input voltage must be approximately 2V above the set output voltage.
If the input voltage is DC, the rectifier bridge can be bypassed to avoid the voltage drop across the bridge diodes (see the markings on the rear of the board).
The regulator requires heatsinking in most applications, as all voltage dropped across it (VIN – VOUT) is dissipated as heat. Note that the exposed metal on the regulator is internally connected to VOUT and should be isolated if the heatsink or chassis it is mounted to is electrically connected to a different potential.
The included screw terminals accept wire cross-sections from approximately 0.5 to 2.5mm².
- Supply voltage: ~4 - 40VDC
- Output voltage: 1.25 - 32V (supply voltage must be 2V higher)
- PCB dimensions: 36 x 36mm
- Mounting holes: c-c 31 x 31mm, ø2.5mm
Errata
Markings for V+ and GND on the PCB top layer are reversed. Follow the markings on the bottom layer!
The incorrect markings will be hidden if the included screw terminals are used, but if wires are soldered directly to the board, please use the markings on the bottom layer.
Component list
| RefDes | Value | Qty. | Part.no. | Marking |
|---|---|---|---|---|
| C1 | El.lyt capacitor 2200uF 50V | 1 | 41024619 | 2200uF |
| C2, C5 | Ceramic capacitor 100nF | 2 | 41003038 | 104 |
| C3, C4 | El.lyt capacitor 10uF | 2 | 40520021 | 10uF |
| D1 - D6 | Diode 1N4004 | 6 | 40310004 | |
| IN, OUT | Screw terminal 5mm 2-pol | 2 | 40210002 | |
| LD1 | LED 3mm red | 1 | 40307000 | |
| R1 | Resistor 200ohm | 1 | 40811220 | |
| R2 | Resistor 2.2kohm | 1 | 40811322 | |
| U1 | Voltage regulator LM317 | 1 | 40350028 | LM317T |
| VR2 | Trim pot 3266Y 5kohm | 1 | 40320001 | Y502 |
Assembly guide
Before beginning assembly, check that the PCB is free of damage and scratches. Verify that you have all components to be installed by comparing against the component list. It is generally easiest to start with the lowest-profile components and work upward by height. Resistors, ceramic capacitors, and diodes are installed first. The regulator, trim potentiometer, connectors, and electrolytic capacitor are installed last. For certain components, correct orientation is critical. Pay attention to the markings on the board.
Interactive assembly guide ↗
Schematic
Drawing
