Dual Power Supply Front End - alt lab supply

thingiverse

An affordable alternative to a dual output DC lab supply. Primarily, a power supply front-end with voltage adjustment buttons, LCDs for voltage and current readings, banana jacks / binding posts, DC jack, and power switch. Built around two DC-DC buck converter boards; output 0-16.5VDC, 3A peak, 2A continuous (times two boards/channels). I haven't tested the power specs to the max, but I did include mounting for a cooling fan (untested). The total parts cost is about 10 USD. It needs a positive tip power supply under 23VDC not included in that total; laptop chargers are pretty much ideal (~20V, >3 A). [Single Output Version](https://www.thingiverse.com/thing:3017793) ## Thanks for the CAD models: [Banana jacks by Jeroen Lodder](https://grabcad.com/library/hirschmann-pki-10-a-banana-plug-1) [Switch by Milan Samardzija](https://grabcad.com/library/rocker-switch-14) [30mm fan by Phil Maddox](https://grabcad.com/library/30mm-dc-fan-1) ## BOM: Find the tip size of your wall-wart/AC adapter before buying the DC jack. Links for 5.5mm x 2.1mm as well as 5.5mm x 2.5mm are included below. The list includes things I suspect most people already have like screws and an AC adapter. Assuming those are on-hand and the fan isn't installed, I calculated 8.44 USD for parts actually used (items 1 - 4 below). I selected parts with free shipping when possible, but some parts have minimum order quantities above what's needed. + 1) [DC-DC converter board, qty 2](http://s.click.aliexpress.com/e/ccfu9LyU) + 2) [Banana jacks, link is already qty 2](http://s.click.aliexpress.com/e/bu8UAXdA) + 3) [Switch](http://s.click.aliexpress.com/e/Q9djqd6) + 4) [DC jack, select your tip size](http://s.click.aliexpress.com/e/T5ecnpq) + 5) [Optional, fan (30mm, 24V)](http://s.click.aliexpress.com/e/cma9N55Q) + 6) [DC DC board screws, M2.5 x 5mm](http://s.click.aliexpress.com/e/ccfu9LyU) + 7) [M3x16mm flathead screws](http://s.click.aliexpress.com/e/bu8UAXdA) + 8) [Adhesive rubber feet (4X)](http://s.click.aliexpress.com/e/Q9djqd6) ## Assembly: 1. Install the buttons; drop in, check they move freely and drop all the way down. 2. De-solder/remove the large blue terminal blocks from the DC-DC converter boards. Clean out (wick or sucker) the plated thru-holes. Adding wires to Vin/GND and Vout/GND may make wiring easier later. 3. Install the DC-DC converter boards using M2.5 x 5mm screws (4X). The screw bosses should be effectively self-tapping. Check that the buttons now "pop" when pressed **and** when released. 4. Install the DC power jack, switch, and banana jacks. 5. Wiring: Use a fairly high-powered iron (GND plane and beefy bananas can suck the heat away before the temp gets high enough to melt the solder). + Solder red wires: DC jack+ to switch_in, switch_out to DC-DC boards' Vin [2X], DC-DC boards' Vout to red bananas [2X]. **Make sure the polarity to Vin is correct!** + Solder black wires: DC jack GND to DC-DC boards' GND [by Vin, 2X], DC-DC boards' GND(by Vout) to black bananas [2X]. 6. Optional: Install and solder in the fan (black to DC jack GND and red to switch_out), not yet tested. 7. Install the bottom cover with M3x5 flathead screws (6X). They should self-tap into the body. 8. Optional: Apply small adhesive rubber feet (4X). https://youtu.be/I5ZASDWc5L0 https://youtu.be/0Hl5d5YSglQ