When I started my company last year, it was mainly set up as a design consulting outfit to pick up a few jobs on the side. At the end of 2014, it became much more when I decided to plunge full-time into my own work. At the time, one of my respected friends and colleagues, Don Powrie of DLP Design, said to me that the only way to make consistent money is to have a product line rather than rely on consulting work. I’ve been thinking of how to bring that to market ever since. I could certainly design some familiar products to me, but they would get lost in the plethora of similar items. I needed something unique.
I only recently purchased a Raspberry Pi 2 and started checking out what I could do with it in the ham radio world. I picked up a ThumbDV from NW Digital Radio
and got that software running on the Pi. The trouble was I only had a 1A USB power supply (the one pictured in the Kickstarter video). Things just weren’t acting right and I started thinking of the best way to get more power to this wonderful platform. As part of my consulting work, I recently designed a Power over Ethernet adapter for another platform and figured I’d do something similar to launch a product. Someone had just announced a PoE to Pi power board. I don’t recall if it was on Kickstarter or not, but I figured it best not to duplicate that effort. While doing a little shack cleaning and trying to consolidate some wires, I asked myself, “Wouldn’t it be nice to use the Anderson distribution panel right to the Pi?” and the light turned on! THERE was my unique product.
I started out with a 5V @ 5A design. I drew the schematic and completed the PCB layout and started to check pricing and availability of the parts. Most everything was available at Digi-Key, and the Anderson Connectors from Mouser, but the total was getting close to where I wanted the selling price to be. For a $35 computer, I couldn’t justify a $70-$80 power board!! The DC-DC converter also had a very large ground pad for heat dissipation. I wanted this project to be able to be hand-soldered and started wondering about that large pad. That design got scrapped and I started looking for another buck converter. There were several TI and Linear products I considered, but they would have required a reflow oven – either with a center pad, as a BGA, or leadless formats. Then I found the Alpha & Omega AOZ1031AI. This is a 8-pin SOIC without any special pad. The only heat-dissipation suggestion was that pins 7 and 8 do not have any thermal relief, but connect fully to the surrounding plane. I selected larger commodity parts (0805) that could be seen without a microscope and created the layout, and all parts were in stock at either Digi-Key or Mouser Electronics. I got everything on order, and even managed to get a couple free PCBs from Pentalogix. I had attended a Pentalogix-sponsored Cadsoft Eagle webinar at Newark and the perk was a code for two boards. I just had to cover shipping.
I got everything in and soldered together. The only issue I ran into was my switch selection. I used a footprint from one source, and the switch leads were just a little wide for the pads. First thing was the multi-meter test to make sure the PCB (both bare and assembled) didn’t have any direct shorts. Next up was the infamous “smoke test”. Plug it in and hope it doesn’t go “Pfffffft!”. Success! (I have a bench supply that I started at about 6V and limited the current to 0.5A just in case). I checked input and output voltages and all was well. The voltage was then ramped up through the specified range with constant 5V output. All this was done with no load. Once I was satisfied that the 5V was stable, I unplugged everything and put it on the Raspberry Pi. I set the bench supply for 10V and turned it on. Yes! The Pi booted and ran normally. Time for a beer!
I did other tests: Let it run for 8 hours (check), ramp voltage from 6 to 18V input (check). At 7V input, the Pi kept rebooting. At 8V, it was solid – well past the design spec. Same at 18V.
Next up was the load test. With 2A going direct to load resistors, I was still able to run the Pi with all four USB ports occupied. I even dipped the supply to 8V. The bench supply showed about 1.8A output. Based on an approximate 80% efficiency of DC-DC converter, I calculated I was drawing about 3.5A on the 5V side – a little past its limit, so backed off the load. I’ve been running this directly from my radio supply now for several days, and the Pi keeps chugging along.
Going the Kickstarter route
wasn’t exactly on my mind when I came up with the product. Much of my career has been with smaller companies where we all wear many hats. I already had multiple products that I had taken from concept to full production. Most of these were one form of communication board or another for the earlier IBM PC and related clones. I was originally going to just launch a web store site, but was having trouble with how to market the concept. I started looking at my available funds and figured a good portion would get utilized without much word getting out with a normal store-only approach. That’s when the Kickstarter site popped in my head. I looked around for similar projects and decided to give it a go. I seemed to have everything in place…. except the video. I’d rather be behind than in front of a camera, so I worked up a script that I hope is fun yet catchy and started recording it. I took a bunch of pictures and found a few on the ‘net (CC licenses) This entire project is created in Ubuntu Linux from the design in Eagle to Audacity, Gimp and OpenShot for the media.
I’m a believer in open-source hardware and software. This project will be published in the coming days, probably on GitHub. Eagle uses XML design files, so version control should work just fine. I still need to write the manual, but everything will be made available as soon as I get the proper README and LICENSE files in place. All of my work for this project is published under the Creative Commons Attribution and Share-Alike license. The hardware itself is published under the TAPR Open Hardware License.
As an aside, in looking for the Anderson Powerpole
connectors, I ran into a disturbing find: About half of the connectors in my shack stock look like they’re fake connectors and housings. Many of them have the “o” missing from the word “POWER” in the stamping. A few have “POWER” upside-down when compared to a genuine housing. There are color and fit differences as well as corroded and inconsistently sized pins. No wonder some my cables were nearly impossible to assemble. I attached a picutre. The left side shows genuine Anderson Powerpole parts purchased from Mouser Electronics, an authorized distributor. The right side shows what I have in my shack stock that I picked up from various hamfests and other sources. Be sure to only get all parts only from authorized sources. I almost never trust eBay or Amazon for this type of stuff.