I decided to have some fun and build my own down converter for my Raspberry Pi. On my first try I used a LM7805 but quickly realized it would not work with 14V and the TO-220 heatsink I had on hand. I saw some videos on the cheap Amazon/Chinese/eBay voltage down converters, and I really wasn’t impressed. They looked poorly made with copied LM2596’s and are probably very noisy, which isn’t good for my radios. I wanted quality and efficiency to use my Raspberry Pi on batteries, so with a few dollars worth of quality parts I managed to throw my own DC-DC step down converter together with the circuit design direct from Texas Instruments above.
- Texas Instruments LM2596 5V – TO-220 Package
- Panasonic FM 680uF 16V Capacitor (Get Higher Voltage!)
- Panasonic FM 220uF 25V Capacitor
- Murata 33uH 2A Inductor
- Fairchild 5A 30V Schottkey Rectifier
- T&K Components SPDT Slide Switch
- PC Board Terminals
- TO-220 HeatsinkTO-220 Mounting Hardware (Just for the screw!)
Overall, this wasn’t very tough to make, though I now realize I made a poor decision on the 16V 680uF capacitor if I wanted to do voltages higher than 16V. I only mainly use around 10.5V with batteries, or 13.75V with my 20A linear power supply, but you may want to look for something around 35-40V when building one. It took me two hours to do all of the soldering even with a cat jumping all over me. It worked on the first try, besides forgetting to give power to the LED. The board layout plan wasn’t that great, but it sure works well. It generates far less heat than my LM7805 circuit, and I know I got quality real parts. I am hoping with 8x Powerex 2700mAh rechargeable batteries, this DC-DC step down converter will give me at least 48 hours of run time on my Raspberry Pi. Doing the calculations, under perfect efficiency they should last 50.4 hours from my load amperage readings.
I am going to see if I can run this on an oscilloscope to see if it is very dirty or not. Its near field RF switching @ 150KHz isn’t noticeable from background noise on my radios from 2ft away. I would consider that very quiet RF wise and would be great for doing Ham Radio on the Raspberry Pi.