Description

This board features four LM317 linear voltage regulators that are independently adjustable, via the four trim pots on the board, from 1.25 to 24V for V_in = 26V or V_out = 1.25 to (V_in - 2)V DC. It comes with a five pin header, that can be soldered into place, which allows the board to be easily used with a standard breadboard. Given a single input voltage, you can have four independently adjustable output voltages. Although the LM317 can handle input voltages up to 37V, we chose to limit the input voltage to 26V and the output voltage to 1.25 to 24V DC. This was, firstly, due to the limited power dissipation of the passively cooled board and secondly, due to the challenges of adjusting large output voltage swings precisely with the single turn trim pots. We believe these compromises were justified and the result is a relatively inexpensive and extremely convenient way to get four independently adjustable output voltages from a single input voltage.

• Includes a 4-output adjustable voltage regulator board
• Includes a five pin header 0.100" (2.54 mm) pin pitch

Notes

• Convenient and relatively inexpensive way to get four independently adjustable voltage outputs from one input voltage
• Linear regulators produce clean voltages with good regulation
• Can be powered using a DC power supply or even a salvaged DC power adaptor
• Plugs directly into a breadboard using the included five pin header
• Linear regulators regulate voltage by dissipating power. See below for calculations to determine safe board operating temperature.
• To keep costs down, single turn trim pots were used. This makes adjusting the output voltages less precise, however we believe this is an acceptable trade-off for the cost and convenience of the board.
• Most trim pots have a low rotational life* and the trim pots used on this board are no different. That being said we believe this is an acceptable trade-off for the cost and convenience of the board.

Specifications

• Thermal overload protection (avoid repeated thermal overload)
• Short-circuit protection (avoid repeated short-circuit and limit the duration of short-circuit)
• V_in (input voltage): 3 to 26V DC
• V_out (output voltage): 1.25 to (V_in - 2)V DC
• Dropout voltage is ~2V so input voltage should be at least ~2V greater than the highest desired output voltage
• I_out(max) (maximum output current per regulator) for V_in - V_out ≤ 15V: 500 mA**
• R_ΘBA (thermal resistance board-ambient): 100°C/W
• Trim Pots Rotational Life*: 100 cycles
• Dimensions: 2.2 x 1.2 in. (56 x 30 mm)
• 2 layer
• 1.6 mm thickness
• 1 oz. copper
• LeadFree HASL-RoHS

*Rotational Life: The number of cycles obtainable under specified operating conditions while remaining within specified allowable degradation. A cycle is defined as one complete traversal of the wiper over the resistive element in both directions.

**This is dependent on the total power dissipation of the board. See calcuations below.

Downloads

The datasheet for the LM317 used on the board is available for download below.