Tag Archives: breadboardpsu

bbpsu-2.0-running

Breadboard PSU Feedback

The time has come to start considering design changes for one of my more commonly shipped projects: The Breadboard PSU. It’s had a few revisions in the time I’ve been making them, most recently moving towards panelisation and automation of more of the build.

Feedback is one of the things which helps me make better things. So the point of this post is to invite people who have bought, used, or seen the PSU to give feedback about it.

At the moment, I have a few changes in the back of my head for the next revision:

  • The 3.3V reg is fed directly from the input voltage. This means it really has trouble supplying much current at all (it’s very thermal limited, since it’s a linear regulator). This should be moved to be fed from the 5V side.
  • The 5V regulator is now going to handle the most load and therefore leak the most heat. The SOT-223 package is not the best for thermal performance, I’d like to re-arrange it for a D-PAK version instead.
  • D-PAK would also allow a more comfortable fit for a heatsink, probably a small 8x8mm one just to try to help improve thermal performance.
  • The MOSFET on the input side for reverse polarity is great for low loss, but is much less critical than I originally felt. It’s slightly less area than a diode. Given the other changes, I’ll probably switch this back to a diode.
  • The DC jack is large and annoying. Either needs to be SMD mount, or possibly take the plunge on JST and include a JST to DC jack cable.

Anyway, feedback is very welcome and I’m happy to answer any questions!

The design of BBPSU

My Breadboard Power Supply is designed to overcome a number of problems with other existing plug-in power supply designs. At a glance, it might not seem to make much difference how my supply board is designed compare to other solutions – they all get you a stable voltage from a wall wart – but read on for how those differences actually matter.

Most Breadboard power solutions provide a single output from a DC jack. This is fine if you know you’ll only ever need one power rail. But increasingly ICs and components are only available with 3.3V, and other components don’t run at their top speed unless being fed at 5V. Having both available at once is more of a necessity than it has been in the past.

For example, Microchip make one of the only Ethernet chips you can plug into a breadboard: the ENC28J60. A small, through-hole IC, which provides almost all the hardware needed to add Ethernet – just a jack, some magnetics, and terminaton is required. But this part is 3.3V only. Similarly, to get the maximum speed out of a AVR MCU you can plug into a breadboard, say the ATMEGA328P (like an Arduino uses), you need to run them at 5V.

So my breadboard supply board provides you both at once. You don’t have to switch between one or the other. Both 3.3V and 5V are available from the same input and the same board.

The second problem with most supply boards is the way they connect to the breadboard. A breadboard has down each side two power rails (usually marked red for positive and blue for ground), and it’s natural instinct to connect a supply board directly to these rails.

But there’s problems with connecting that way. Not all breadboards have the same width. The main area of a breadboard, the grid of holes, is always spaced the same, but the number of columns varies between breadboards, and the distance from the grid to the power rails varies as well. This means most supply boards will either only connect to a single side rail or if they do try to connect to both, they are only able to connect to a few specific breadboards.

Instead, I noticed there’s one area of a breadboard which is always consistent – the IC well. Breadboards are designed to accept all DIP packaged ICs, their pins are always spaced on a 0.1″ grid. So all breadboards have their grid spaced the same way. And to split the sides of a chip into separate lines, they have a well down the middle. That too is spaced on the same 0.1″ grid, to ensure any DIP chip will fit.

That’s the better, more reliable, place to connect a supply board – it’ll always be the same spacing on any breadboard. Since it’s also split between sides, it makes it easy to provide both 3.3V and 5V at once – they are just different sides of the IC well.

Most supply boards droop off the end of the breadboard, which is both sloppy and may damage the breadboard or pins in the supply board. My supply board uses additional pins to provide stability, so there is no droop and the board and pins are firmly held in place without bending.

The LEDs for each side are also placed nice and close to the pins where the output is present, so you can see easily that each side is live. I’ve also put more emphasis on limiting the number of components down to what you really need, and not things which aren’t critical to have. This means my supply board is much cheaper, about 30% cheaper than other boards with only a single output, and you get two outputs from my supply board.

It’s also been designed to be easier to install a small heatsink on to the regulators. Linear regulators do generate a significant amount of heat, but most boards try to cram too many components around the regulators, making it hard to use a small heatsink to improve how much current can be drawn from the supply board.

By keeping the space either side of the regulators clear, it’s very easy to glue down a small heatsink designed for DIP packages to both regulators. Very few supply boards can accept a heatsink this easily.

Lastly, buying locally means you get customisation options. The boards can be supplied with custom voltages, or without pins or DC jack loaded so you can solder it into a fixed installation.

In summary, the hairy.geek.nz breadboard power supply:

  • Provides two outputs at once, instead of only one
  • Prevents damage to the breadboard by limiting droop from the power input
  • Fits to any breadboard
  • Provides a clearer indication power is on
  • Ensures you can easily install a heatsink if required
  • Is lower priced than most single-output boards
  • Can be customised to your specific needs

You can get the hairy.geek.nz Breadboard PSU from nicegear here.

BBPSU 2.0 available now!

A quick note to report version 2.0 of the Breadboard PSU is now available from Nicegear.

They come fully assembled, so you can rip it out of the package and drop it straight into your solderless breadboard to get started.

This version, despite being significantly smaller is actually just as capable as the old version, and still supports custom voltages if you need them. They can also be sourced without any connectors or pins installed, if you are using them for a permanent install. Best to contact Nicegear if you’d like those options.

And for those of you looking for a way to power your Arduino from a higher voltage source, check out our Wide DC Supply Shield Kit which makes it easy and safe to use a DC input between 9 and 37V DC. No excessive heat or exploding capacitors on your Arduino!

Testing

The second part of getting up to better production standards is testing. While I’ve always done testing, it’s usually a slow process of fiddling with sockets and checking each point with a multimeter by hand.

For v2.0 of the Breadboard PSU an important design decision was to include better support for being able to test the assembled boards quickly. The intention was to take advantage of one of these.. a pogopin:

pogopin

Pogo pins are a spring-loaded conductive pin which can be soldered in like a header pin. They are small enough to fit standard holes boards already usually have for various kinds of headers, and come in a variety of tips, including ones which make solid contact with flat exposed pads.

The output sides of the board already have useful holes to connect a pin to, but the input side didn’t have anything. So v2.0 has two holes down by where the DC jack is soldered specifically for pogopins during testing.

The next part is making the testing frame. For this, I used the laser cutting services of Ponoko. These are the plastic cuts I designed and had cut:

The three pieces make up a bottom layer to hold a sacrificial PCB, and two top layers, one of which is just used to assist on placing the board. The small holes are to allow the pogopins to pass through, with bolt holes in each corner.

The sacrificial board is one of the boards from the panel with nothing soldered down to it. Pogo pins are soldered down on the existing holes, and additional wires are soldered to pads and holes which connect to the same signals.

The whole contraption, connected to a pair of multimeters and a DC jack, looks a bit like this:

From the side, you can see the way the pins are arranged to allow contact from a board under test:

This is probably not ideal, the pins are too high, but you get the general idea.

All that needs to be done now to test a board is press it down on the array of pins, and check the meters and LEDs are lit:

As you can see, the LEDs are lit confirming that they’ve been soldered down correctly (for once!), and the voltages of both sides of the output. This board was rejected after testing, as the 5V output is too low.

Testing is a critical part of making sure the products you make are working as the end user expects. By using a testing jig like this, I can test a board in about 5 seconds.

Using a small MCU, a more complete testing platform could be made, that automatically measures voltages, or flashes firmware images, or interrogates the target board to ensure it operates normally.

All you need is a bed of pogopins, and some imagination.

Panels

As part of expanding my production processes, I’ve taken the next step in production scale: panelised boards rather than separate boards. The idea behind this is rather than applying paste to one board, you apply it to a panel of boards which has multiple copies of the design. Once reflow is done, you can split these by hand into final boards you want.

For the newest revision of the Breadboard PSU, I got panels made by Hackvana, who do fantastic high quality PCB production ideal for hobbyists like myself. I worked with Mitch from Hackvana on the panel, providing a single design and then approving the panelised version he’d built. Only a few days later, the panels turned up, and they looked great.

To actually get them soldered up and ready to ship out to Nicegear, it’s almost the same process I normally would go through for a single board, but now it’s multiple copies at once.

The process begins with applying paste to the board. Here you can see the multiple copies making up the panel, and empty board around the outside. There are four holes in the corners which align with the holes in the metal plate below, and have 2.5mm pins in them. The stencil is taped down on top of the board, and also has holes where the pins are.

Applying paste is just like you would for any other board, smear solder paste on the stencil, and then scrape it off. Once you’ve removed the stencil and released the board from the pins, you get a panel with paste applied to the pads:

The grey paste can be clearly seen on the pads here.

Now we go through the process of dropping down our components. I use a vaccum pump with a fine tip I bought from AliExpress for this part. It makes it easier to lift the parts straight from the tape on to the board.

Once we’ve placed all the parts, the board looks like this:

Now we’re ready to cook the board. I have a “modified” toaster oven driven from an SSR by a PID controller called osPID. The reflow profile is loaded into the osPID controller and it pulses the mains into the toaster oven to hit the temperatures the profile needs. There is a thermocouple inside the oven so the osPID controller is getting closed-loop feedback of how the oven is performing.

This is the board being cooked in the toaster oven:

I try not to burn my fingers when removing the boards from the oven after the reflow process is done. You can see in the photo below the bright silver solder, showing it’s now all soldered down:

Now we just need to start breaking the panel apart into the separate boards. Hackvana have used a v-score cut along the dividing line between boards and the boards and rails, so they can be snapped apart by hand easily.

Finally we have all our boards separate and ready for testing!

Once all the through-hole soldering is done, we get our nice shiny finished product, ready to be sent out into the hands of eager users!

Project Updates

A few small updates on the state of various projects..

NTP Server: Version 1.5 board looks mostly final now. The 3.3V switchmode regulator design has been checked on a breadboard and seems to run 1.4 just fine, so we’ll be going with that on the 1.5 board. This will reduce the heat significantly, as the reverse-polarity diode (which itself loses about half a watt) is being replaced with a P-channel MOSFET and the switchmode supply loses far less heat compared to the linear regulators (almost 1.6W are sourced from them alone). Software side I’ve removed all the (hugely problematic) single precision floating point code and use the time reported in integer milliseconds instead. Much nicer!

AVR Programmer: First build has been completed, and it largely works with the LUFA code compiled and uploaded into it. Various issues have come up, such as the bootloader switch not working quite as expected (The bootloader will only enter DFU mode if the switch is closed and we’re coming out of external reset which isn’t just a power-on-reset. Ick.) External flashing of the MCU doesn’t work right (unsure why) and it seems to hold !RESET low on targets. There is a 1.1 which is in progress.

New Breadboard PSU: Following on from the tests on the new switchmode supply for the NTP server, I’ve sketched out a new breadboard PSU which uses the same design. This would be an alternative to the linear one I already make and sell. At the moment it’s a single output design, I’m thinking about ways to make it dual-output or at least easily switchable between 5V and 3.3V.

XMEGA Arduino: Most of this design is completed. I need to just do a build to see how it plays out. The new XMEGA C3 line looked interesting but imposes some annoying routing problems. While using the C3 would provide a USB XMEGA which isn’t encumbered by crypto modules (and, therefore, export regs) and the C3 has USB pins where they are on the AxU chips, it has the same selection of peripherals as the D3 and USB is camped on top of one of the SPI ports. Which makes routing hard. May stick to the D3+MEGA16U2 bridge approach for now.

 

First production run of power supplies

The first production run of Breadboard PSUs has now been completed. They’re all ready to ship in anti-static bags after being tested to ensure they’re working fully. It’s quite a strange experience to be the one putting things into anti-static bags, instead of ripping them open to get at the shiny shiny things inside.

I haven’t yet sorted out how these are going to be sold, or pricing. If you’re interested in grabbing one, drop me a note and I’ll work something out. The documentation page linked above also needs to be updated with the correct datasheets and a diagram of the board.

First build of Breadboard PSU complete

Completed the first build of the Breadboard PSU project today, since Ponoko had finished making the paste stencil and element14 had shipped at least some of the diode I am trying out on this board.

Thanks to the great stencils cut by Ponoko it was fairly quick to assemble and thankfully worked first time. While it’s a very simple board, it’s still been interesting putting it together.

I am not sure exactly how I’m going to sell these, assuming I work out anyone wishes to buy them That’ll be the next step of the plan!

Below is the competed board plugged into the tiniest breadboard I have around. I think it makes it much easier to use those little boards for trivial projects too. (The rails top/bottom are not connected to it, you’d need to run a couple of wires from the sides of the board to the rails..)

New boards!

A shiny new collection of boards arrived today, so they’ve been unpacked and stuffed into storage awaiting being built up!

This is the first run of boards for the Breadboard PSU project, which now awaits some missing components and then a stencil to be cut by Ponoko. Hopefully in a week or two we might actually have completed some boards and have them available to buy!