insideGadgets

A small programmable power supply based on the LM2596 module found on Ebay. An ATtiny44A controls the 4 digit LED segment display and features 3 programmable buttons with a rotary encoder with digital potentiometer to adjust the output voltage.

Auto calibration is supported in steps of 0.1-0.2V which means that one click of the rotary encoder equates to 0.1-0.2V change in output voltage (but higher steps occur due to design when you reach 5V and up).

Specifications
PCB Board: 100mm x 50mm
Input voltage: 12-15V
Output voltage: 1.8-12V
Ripple: under 70mVpp (no load), under 160mVpp to 4V (10 Ohms load), under 100mVpp (47 Ohm
load) – not the best but it’s mostly due to the LM2596 module.
Weight: 68 grams

Download

The download file includes:
– Source code and compiled main.hex file
– Parts list and instructions on use (View the PDF)
– PCB Guide
– Schematic
– Pictures of finished product

v1.0 (11 May 2014)
– Initial Release

Example calibration information

Each step of the knob when turned would result in a change shown below.

Voltage  Change    Voltage  Change    Voltage  Change
1.74               3.68     0.17      6.03     0.15
1.82     0.08      3.82     0.14      6.23     0.2
1.94     0.12      3.94     0.12      6.44     0.21
2.08     0.14      4.06     0.12      6.64     0.2
2.2      0.12      4.17     0.11      6.87     0.23
2.32     0.12      4.29     0.12      7.1      0.23
2.43     0.11      4.46     0.17      7.36     0.26
2.55     0.12      4.64     0.18      7.68     0.32
2.66     0.11      4.78     0.14      8        0.32
2.78     0.12      4.9      0.12      8.35     0.35
2.9      0.12      5.1      0.2       8.76     0.41
3.01     0.11      5.22     0.12      9.22     0.46
3.13     0.12      5.33     0.11      9.71     0.49
3.24     0.11      5.45     0.12      10.27    0.56
3.36     0.12      5.59     0.14      10.9     0.63
3.51     0.15      5.74     0.15      11.66    0.76
                   5.88     0.14      12.06    0.4

Buy

This kit requires assembly and soldering, you will need your own parts. To reduce shipping costs the kit is sent via the Airmail letter service for $3 and the usual delivery time is 7 – 12 working days (however it sometimes can take 20 working days depending on your location); we ship via Australia Post.
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Small Programmable Power Supply PCB board only – $7
This is for the bare PCB itself, no components are included.

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This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License.