Lab PSU cabinet with temp-controlled cooling

Description

This is about 90% the same as the excellent ["perfect ATX Lab PSU cabinet"](https://www.thingiverse.com/thing:4600323). The overall case and design are largely the same. My main modifications and additions are: * Shortened the main case and side panels 10mm to fit on a 210x210 Prusa i3 MK3S(+) bed. * Extended the front panel to compensate for the shorter case and allow more working/wiring space. * Replaced the first buck/boost converter with a higher step-up voltage model, allowing the adjustable voltage module to reach 50V output. * Used a different power switch model that's wired directly to the PSU (eliminates 2nd buck/boost converter). * Added a temperatures probe and custom circuit that only turns on exhaust cooling fan if the enclosure gets hot. * Created an alternate enclosure main body with back side compatible with older ATX (pre-v2.0) PSUs which had a different physical rear layout. The first two points and last point are what really got me modifying what is an otherwise great design as is. I happen to have several 200-300 watt ATX 1.x supplies that still work great and have plenty of power for this application. Unfortunately, I realized after printing the main enclosure that the power plug, power switch, and mounting screw placement on these old (~2003 and before) supplies is different from the newer ATX 2.0+ layout. I also wanted to be able to print the enclosure on my Prusa. Its bed is 10mm smaller than that used for the original design so I had to modify the main enclosure piece. This size reduction would have made a very cramped interior for the wiring. I re-added the missing depth to the previously flat front panel. There were a few changes to the circuitry I mentioned above. Because of these changes, it also made sense to re-arrange some of the internal mounting points and wire holds. I also added a circular bracket to hold the cylindrical thermal probe for the fan speed control. I've included the Arduino sketch and a schematic for the fan controller for those interested. It will require soldering your own bread board and tracking down a few extra components. If you don't feel this is worth the effort, you can hardwire the exhaust fan as per the original design. I didn't want the extra fan noise all the time so it will remain off unless things get too warm (interestingly, I've never once had things get over the ~90F threshold for the fan to kick in). I've included models for both a newer ATX supply and very old (~2003 and before) ones. These should otherwise be equivalent and work with the extended front panel. Also included is a wiring diagram for everything I stuffed in my cabinet. Note that the diagram is for an older ATX 1.x connector. The newer supplies will have extra pins on one side. As long as you use the portion that is the same, you can use the diagram without any modification. ###Parts list Many of the parts are the same listed and used on the source build's details. Some of these are likely cheaper via Aliexpress but I got impatient and bought some from Amazon :) * ATX power supply - Any old one you have laying around, or buy a new one * [USB charger](https://www.amazon.com/gp/product/B08LDC86Z9/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1) * [Power switch](https://www.amazon.com/gp/product/B07D2C95GY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1) * [Boost converter](https://www.amazon.com/gp/product/B08DNDYFQD/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1) * [M3 threaded inserts](https://www.amazon.com/gp/product/B08BJD3W4X/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1) * [Cooling fan](https://www.amazon.com/gp/product/B00VXTANZ4/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1) * [ATX extension cable](https://www.amazon.com/gp/product/B000FL60AI/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1) * [Adjustable output voltage unit](https://www.amazon.com/gp/product/B01FNVESV2/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1) * [Volt/Ammeters (3)](https://www.aliexpress.us/item/2255799920107121.html) (Be sure to check you are buying the color you want; I used the Red/Green/Blue) * [Fuse holders (with fuses)](https://www.amazon.com/gp/product/B01FNVESV2/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1) * Binding posts - I wanted something higher quality so these are different: * [Green (1)](https://www.newark.com/deltron-components/552-0400/insulated-terminal-16a-solder/dp/45M6869) * [Yellow (1)](https://www.newark.com/deltron-components/552-0700/binding-post-16a-panel-yel/dp/94AC9732) * [Red (1)](https://www.newark.com/deltron-components/552-0500/insulated-terminal-16a-solder/dp/45M6870) * [Blue (1)](https://www.newark.com/deltron-components/552-0200/insulated-terminal-16a-solder/dp/45M6868) * [Black (4)](https://www.newark.com/deltron-components/552-0100/insulated-terminal-16a-solder/dp/45M6867) #### Optional - Temperature-controlled fan controller If you decide to also build the optional temperature-controlled cooling fan circuit, here are the parts you'll need. Note that for the ATTiny85 microcontroller, you will need a way to program it with the attached Arduino sketch. You can also modify the sketch to set different temperature thresholds for the fan to turn on at 25%, 50%, 75%, and 100% duty cycle. * [Temperature sensor](https://www.thingiverse.com/thing:6210300/edit) * [ATTiny85](https://www.amazon.com/gp/product/B00PT4XU04/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - Other microcontrollers should work just fine but you will have to adjust the schematics to match. I like the ATTiny85 because they are cheap and work really well for simple applications like this. * 1k resistor (1) * 4.7k resistor (2) * [Switching diode](https://www.amazon.com/gp/product/B079KJ91JZ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1) - You can probably get away with most any diode. I just happened to have a lot of these. * 9014 or similar NPN transistor

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