Tag Archives: custom PCB

ATmega328 on board for near space launch

A Maker named Ugifer recently sent a box of electronics attached to a balloon approximately 124,000 into the air.

As Alan Parekh of Hacked Gadgets reports, the balloon was tracked using the Space Near Us system, with Ugifer creating a custom PCB to keep the circuit as robust and compact as possible.

The finished PCB includes an NTX2 radio module, microSD card, DS18B20 temperature gauge, Ublox GPS, a Honeywell pressure sensor and Atmel’s stalwart ATmega328 microcontroller (MCU).

[Atmel’s] ATMega328 MCU is a great option because it can be programmed from the very easy Arduino IDE,” Ugifer explained.

“It will also run on 3v3 but only a 8MHz. However that’s plenty of processing power for reading a GPS and running a low baud-rate radio.”

Interested in learning more? You can check out the project’s official Instructables page here and the HackedGadgets write up here.

IR reflow in your home lab

While at the EELive! conference last week I met up with the PCB-POOL folks. I first heard about this PCB fab house from my buddy Wayne Yamaguchi. Despite their being located in Ireland, Wayne said they were getting the prototype boards to him in a week. Best yet, at that time, they did not charge extra for non-rectangular board shapes, and Wayne’s boards were all round, used to convert a Maglite flashlight to an LED flashlight.

What caught my eye at the PCB-POOL booth at EELive! was a card that had a toaster oven picture and the headline: “Create your own solder reflow station.” Now it was Wayne that tipped me off about doing reflow for prototypes in your garage. He too used a toaster oven. He just did a few experiments on when to turn it on, when to put in the PCB and when to turn it off. He said he decent results, but the problem with this is that it is an essentially uncontrolled process.

PCB-POOL_reflow-controller-oven

This card was from the PCB-POOL booth at the EELive! conference in 2014.

Enter PCB-POOL. Sure, they sell the toaster ovens. The real deal is they sell the third version of a controller so you can create a profile on your toaster oven. Please don’t use the toaster in your kitchen; flux is not the best butter for your English muffins. So like the picture explains, buy the reflow controller from PCB-POOL for $315, get a brand new toaster oven for 80 bucks, and if you order 5 PCBs from PCB-POOL, they cost 30 dollars each, and PCB-POOL gives you a free solderpaste stencil with the order.

A solder stencil is a thin steel sheet that is laser-cut to have the pads of your circuit board. You carefully position it on top of your bare PCB and then you can squeegee solder paste over it, like doing ink on a silkscreen. Only instead of ink, you are deposing a thin coating of solder paste on all the places where surface-mount parts will mount.

Solder-stencil

This is a solder stencil, with laser or photo-etched cutouts for where you will put solder paste on your prototype PCB.

Now that you have the solder on the pads, the surface mount components will just stick to the board and self-align as the solder melts. Sometimes you can even put parts on both sides and use the solder paste to suspend the parts on the bottom. For heavier parts on the bottom you need a dab of hot-wax or silicon to keep the part in place through the reflow process.

The great thing is that your reflow process has a real temperature profile, like it should. I assume the controller has a SCR or maybe it is just a bang-bang controller that cycles power to achieve a given profile and temperature. The more control you have the more repeatable your process. One nice thing about using the stencil at all is that it proves out your CAD padstacks. If you made some part and forgot to put a solder paste element in the pads for that part, you will realize it really quick when you see there is no solder paste on those pads. This lets you fix your CAD file before it goes into production.

The next level would be to send the whole board to an assembly house like Screaming Circuits in Oregon or Advanced Assembly in Colorado (right down the street from Advanced Circuits, but a different company). Indeed, the first outfit I saw giving out free stencils was Sunstone, which is near Screaming Circuits in Oregon. When you send your fabbed boards to these small-lot assembly houses you are doing more than just sparing yourself the headache of soldering up the board yourself. You are proving out the solder-paste file from your CAD program, as well as the “insert” file as OrCAD 9 calls is, what the pick-and-place machine uses to place your components on the board before reflow soldering. Now you might find that the TO-220 parts have an insert location way off to the side and won’t let the machine vacuum pick them up. So when the nice folks at Screaming Circuits explains this to you, you can fix the CAD files before they go into higher volume production. The real job of an engineer is to make a set of comprehensible coherent documentation that lets the manufacturing world make lots of your design. This is every bit as important as getting the chips to work and the firmware to run.

Most all the fab houses can hook you up with short-run assembly. Some can have your prototypes hand-soldered; many need 3-feet of tape and reel parts so it fits in their machine. That is the cool thing about Screaming circuits, they have adapted their machines so you put in 4 or 5 pieces on some DigiKey cut-tape and make just 5 boards with no parts left over. And don’t forget my pals at Sierra Proto Express. It was Ken Bahl who created the whole short-run prototype concept 20 years ago. These days they specialize in high performance boards, down to a few mills or many ounces of copper along with blind and buried vias. Best yet, they have a partner in China, so when you are ready for high-volume, they can guarantee the partner can make any board you had made at Proto Express.

Building a Mini 7-Segment Clock (V2)



Kevin Rye recently re-designed his already impressive Mini 7-Segment Clock using an SMD version (instead of 28-pin DIP) of the ATmega328 microcontroller (MCU) and a custom PCB.

“I moved the switches a little off-center to the right and shuffled everything else around in order to fit the SMD ATmega,” Rye explained in a recent blog post.

“I rotated the ATmega 45 degrees. I think chips look cooler when they’re rotated, but in all seriousness, it is easier to run a trace from one side of the board to the far side of the chip when it’s rotated.”

Rye also moved most of the (PCB) text from the front to the back. However, with the exception of the ICP and FTDI headers, the board layout remained the same.

 After receiving his new PCBs, Rye decided to kick off a limited test of his new design.

“I didn’t want to put the whole thing together and find out that it didn’t work, [so] I decided to only solder in the ATmega, the 16MHz crystal, and the supporting caps and resistors – just enough so I could test loading the bootloader onto the ATmega and upload a sketch,” said Rye.

“I configured my Arduino Uno (ATmega328) as an ISP and attached the Mini Clock’s 6-pin ICP header to the Arduino via a ribbon cable and some jumpers. I then jumped into the Arduino IDE and burned the bootloader for an Uno.”

After successfully running the bootloader, Rye connected the FTDI adapter and uploaded the blink sketch, jamming an LED into the PCB and watching the LED blink. Last, but certainly not least, Rye validated the ICP and FTDI functions and soldered in the rest of the components.

Interested in learning more about version two of Kevin’s Mini 7-Segment Clock? You can check out his detailed project blog post here and download the source files here.

The art of pixels with Game Frame

Game Frame – a grid of 256 ultra-bright LED pixels – was designed by Jeremy Williams to showcase pixel art and old school video games. As Williams notes, video game artists used to draw everything with a sheet of graph paper, a few colors and a couple of animation frames.

In spite of the obvious technological limitations, says Williams, games devs created some of the most iconic and nostalgia-packed imagery of the late 20th century – the very symbols and mascots of the video game generation.

“Out of necessity grew an enduring visual art style. No longer limited by resolution or power, some game designers still choose pixel art today instead of smoother, glossier options,” Williams wrote in a recent Kickstarter post.

“Why? It’s abstract, vibrant, nostalgic, and LEGO-like in its architecture. It stimulates our imaginations, and surprises us with artistic creativity. It draws comparisons to pointillist painting and stained glass, and I say it deserves a frame.”

Enter the Game Frame, which Williams describes as a slick digital photo frame for pixel art. More specifically, each pixel is projected by a powerful LED via a mesh chamber and onto a sheet of white vellum. Colors are strictly isolated, while a black overlay sharply defines the grid.

“Since there is no global backlight, the visual effect is like a mix of traditional movie screen and OLED. It’s quite unique,” he explained.

“Thousands of images and animations can be stored on SD and played back automatically according to your taste, configured by two buttons on top. You may want to find some classic video game sprites, or draw your own in your favorite editor.”

Graphics are typically saved as BMP files, while the Game Frame is pre-loaded with over 40 new animations from eBoy. The hardware is AtmelArduino (custom PCB, + Adafruit Neopixel library) based and Williams says he plans on releasing the complete source source code once shipments begin.

Interested in learning more about the Game Frame? You can check out the project’s official Kickstarter page here.

This robot is a self-balancing teaching tool

Sean Hodgins recently debuted the PiddyBot, a mini balancing robot designed to teach the basics of PID controls.

Key project components include potentiometers, an Atmel-based Arduino Nano (ATmega328), custom PCB, two geared motors, dual motor driver board (Sparkfun), wheel set, 6 DOF IMU (Sparkfun), 3D printed body (Thingiverse), 2x battery connectors, 2x lithium batteries, M2 screws for motor mounting, female jumper cables and headers.

“First I figured out how small I could make the PCB and still have everything fit. I actually made the PCB a long time ago and it was one of the first I made, so I probably could have made it smaller; I’m happy with the size now,” Hodgins explained in a recent blog post.

“I designed it to have the Arduino just basically fit right into the center of it, that way all the connections are good and secure and it just makes it easier. The size of the board determined the size of the body – I made it so the PCB was basically the only thing requiring any assembly.”

On the software side, Hodgins says the code is in “no way finished,” although it does allow for basic PID tuning.

“It is pretty rough, if there are any questions at all, don’t hesitate to ask! There is a little extra feature in the code, it actually has a sort of positioning return system even without encoders,” he added.

“It basically takes the amount of time the motors are tuning in each direction and the speed and figures out how far away it is from its first position.”

Interested in learning more about the PiddyBot? You can check out the project’s official page here and download the PiddyBot Arduino code here.