Steve's Build Log


#41

I have started another project. This time I have decided to join the NeoPixel crowd. Though I doubt it will be ready for this Christmas.
Rather than taking what is out there or using an Arduino, I have opted to try this from scratch. In my designs I am leaving it open as to what MCU I will use for further projects but I at least want to give the ATTiny1614 a go in this version. My current understanding is that it is supposed to support 20Mhz without an external Crystal. The small number of GPIO and 2K of RAM makes this attractive for my intended use. I am just not sure if there will be any timing issues by not having a crystal while it is said that the NeoPixels protocol is timing sensitive.

An interesting outcome of starting to look at the protocol for the NeoPixel and the MCU I have chosen, programming of this little fella is different again to the others I have been exposed to. This is using what Ateml refer to as UPDI … it is basically a single wire protocol as well so the program header only needs three connections - data, V+ and GND. With this programming protocol it is supposed to also support debugging. I will be curious to see how this all comes together.

I want to keep this as compact as possible, which is another reason for going with a smaller MCU. Even so, I have broken out what few GPIO it has incase I find another use for the board as well as for testing.
The documentation for the NeoPixel says to use a 1000μF capacitor at the supply end if powering from a power adapter. In keeping with a compact design, I am going to try mount this under the board.


#42

Wowsa, that capacitor is huuuuge! :slight_smile:

The schematic you linked has “3V7 in (Nominal)” and the LM2621 (and that configuration) makes me think it’s a boost. So is there a disconnect somewhere? Is it going to be a step down or a step up?


#43

Thanks for the proof read :slight_smile: I was mixing it with a battery charger stage that I still need to think through. I have corrected my post.


#44

3V7 to 5V Boost Regulator Prototype
The boards for the prototype boost supply arrived yesterday and the parts I needed arrived today. I could not wait and had to put this together. The BOM for this sample had suggested a couple of 0402 resistors. I deliberately left these to try them out. This was my first time with such a small size. I had decided on the out-set that I would not be soldering these by hand and ordered a stencil. I was just unsure how the polymide stencil would work the 0402 size, so I decided to use a stainless steel stencil - also for the first time. I was not disappointed! The application of the solder went on easy. Though it did look a little thick.

After the re-flow, I am very pleased with the result. Only one resistor, an 0805 went walkabouts on the board but that was easy to put back in place. There was no other movements and no bridging on the Boost regulator. This would have to be one of my best efforts.
I was also delighted to find that there were no problems in bringing the board up. It powered up nicely and the initial wave forms look OK. The sample shown below is a 3.7V 500mAh LiPo (I used my lab supply on the initial power up, just in case there were any issues).

This is not the end of the testing. When I get a bit more time, I will be brushing the dust off the Current Sink or Swim and putting both the regulator and the battery through some further tests - this should also test my memory in the use of the CSOS!

The end result is that I am very pleased with the stainless steel stencil and for the price, I will definitely consider them for future, but not all, projects. As for 0402. I don’t know if I would be using them more often. In the end, they were not a problem but placement was a little cumbersome. Luckily for this board, I only had three to worry about.


Jon Thomasson's Build Log
#45

That board came out beautiful, great job! For the stencil, did you have to setup a jig to get it positioned precisely where you needed it? Or is it just a matter of taping things down?


#46

Thanks Jon. I just use the jig that OSH Stencil can provide and tape things together on the the back. I then taped the stencil down onto the jig. This board is really small so I did not experience any issues with that setup. I must say, though, the stainless steel seemed to align much easier than the polymide. maybe it is because the polymide is transparent and that make it a little harder to identify that the smaller pads are lined up correctly.

I would really recommend to anyone attempting to use the stencils for the first time (or the nth time) is to listen to episode #320 of the Amp Hour - “An Interview with Brent of OSH Stensils”. This has been a huge help in understanding how to use stencils better.


#47

I found this as well. They aren’t markedly different from their larger brothers, but they just seem to require a lot more concentration when using tweezers. And since they still seem to be the line of demarkation between DIY/low cost pick and place and the mid-range pick and place I think it’s still a better bet to go with larger sizes if possible.

Me as well. I find I likely won’t go back to polyamide unless truly cost constrained. The price keeps dropping on the SS ones and I’m sure that they could be used for 10s of iterations instead of the 5 or so the plastic ones allow.


#48

That’s so neat that they even provide a jig with the purchase. I have at least one board in mind where this would really save a lot of time. Which oven are you using for the re-flow?


#49

“Provide” as in you have to place it on the order :slight_smile:. I have only ever needed the one and it cost $5.00 at the time.


#50

I have been trying my hand with Integrated Light Sources i.e. NeoPixesl. I have put together my working in my Blog.


#51

I have reached a new milestone. One of the projects that motivated me to seek out a tool such as KiCad and lead me to Contextual Electronics was the idea to replace our stairwell lighting system with a control unit of my own making. The old control system was made of discrete modules and has operated flawlessly for the last eight years. Today I managed to install the new unit, powered by an ATTiny20. The scope has changed since its original inception and so the unit communicates with a Raspberry Pi and I can change the behaviour over a Web User Interface.

I can only hope this new one will operate with the same reliability for so long. The trouble is, the new set up will allow for all sorts of new additions and changes. So leaving it alone will be the challenge.


#52

Looks great Steve! Congrats on reaching that milestone. I really like the enclosure you chose, being able to see the modules and blinking lights through the windows.


#53

Thanks Jon. Unfortunately the LEDs on the Raspberry Pi are at the side of its enclosure and you can’t see them here :slight_smile:


#54

I have created a write up to give closure to the Timed LED Lighting Project and describe the change of direction from the previous posts.


#55

In playing with the NeoPixel board I created, I got curious to see how this could be expanded. I settled on using a 74HC595 Shift Register as a way to address the strips. I then use the enable on the Shift Register to send the colour information to the strips. This has the advantage of being able to send the data in parallel to only those strips that I want to receive the data.

I have a more detailed write-up on my Blog and also put together a short video to demonstrate the results.


#56

Oh that’s really neat. I may have to grab a few of these. For size-and-weight critical applications like the HAB tracker I’m working on, this seems better than a 2x3 .1" header.


#57

Hi Juliean, I have been using these for a while now and have not turned back. The “No Leg” variant is the smallest since it does not need those four larger holes. It just needs a retaining clip to keep the programmer header in place.
I was at Embedded World last week and saw their Edge Connect version. This looks really interesting, as it takes up no real estate on the board. Just along the edge. I will need to check with @fustini (OSH Park) if this could be supported.

[edit]
I just checked the OSH Park Docs and found their note on Castellated Edges. I will simply have to give it a go and see how it turns out.


#58

The comment from @jgalak reminded me I wanted to eventually try out the Tag-Connect Edge Connector.. So I have submitted a board with a couple of foot prints I have created.

I don’t have the actual edge connector yet. But I did pick up one of their sample boards at the Embedded World. I can use that as a comparison.


#59

I used the Texas Instruments WEBENCH® to come up with another power regulator. This time I wanted 5V from a range of 6V to 18V. The initial testing is positive in that it gives a clean 4.92V from 5.5V to 18V (I did not push it higher than that since 18V is already over what I expect). Below 5.5, the system drops out. On the circuit I added the provision for an additional battery backup. The thought was for 4xAAA cells to provide a short-lived 6V. At this stage, I am not worried about the 0.08V discrepancy as I am not yet sure if some of my part substitutions had an effect.

What was interesting is that without load, anything below 6.7V would also show an unstable output. For the initial testing, it was easy to add a 9V battery connector instead of the 4xAAA cell holder. I can imagine the 6V battery pack can still be used once the module has a more permanent connection to the load.

I find using the WEBENCH® a great way to get an in-road on using some of these power devices. The generated design gives all details down to BOM and suggested layout. The simulated thermal images are also pretty neat.

For this design particular design, I took up the WEBENCH® feature and swapped out the 0401 parts for 0805 parts to simplify assembly.

I have to admit, it does not feel like my design. It is more like a kit to my specification. At best it is implementing the application note without having to calculate the specific RC values. Time will tell, of course, on how this design will stand up when the module is really put to work.


#60

Looks good Steve! WEBENCH® looks like a really useful program. I like the simulated thermal image view.