Shift Register Board Rev C – Vias everywhere!

Hindsight is 20/20, that’s for sure.

I’m currently waiting for Revision B of my 74HC595 Shift Register Boards in the mail. I’m eager to get them because they’re my first manually routed boards so I want to see if they turn out right. The revision is a minor one with the only real changes being a connection that was missing in the first revision and breaking out the Output Enable pin.

I plan on using 3 or 4 of these boards for an update to the Light Show. I only checked yesterday to see if I had enough shift registers. I don’t. I started looking around for some more and I quickly realized that using the SMD version of the 74HC595 would have been cheaper. That’s why I’m looking at another revision already…

SRrevCI’m not sure how likely it would be for me to get these made since I already have the new boards coming in but I was really excited to start this design anyway because I haven’t use SMD components very much. The only board I have used SMD components is my AMS1117 board, but the circuit was so much simpler… and at the time, I was new to Eagle so I just used the auto-router.

It’s an interesting adjustment for me to have everything start on the top layer of the SMD ICs. I ended up adding a lot of vias. There are vias that are only there to make a gap for the fill to reach some of the pins. I’ll have another go at it to try and clean some of that up.

Since I’m still new to Eagle, I like to go to websites like Adafruit and browse the boards to see how they’re laid out. I’d like to make my boards as pretty as theirs. That’s one of the reasons I’m trying the rounded corners again, which I didn’t do in Rev B for whatever reason…

Thanks for reading! If the mail service is good, the new Rev B boards should be here in a couple of days. Fingers crossed!

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74HC595 Shift Register Board Revision B Preview

I said when the year began that I wanted to get back into Eagle and revisit some of my PCB designs, as well as start some new ones. My first project for the year in Eagle is giving some attention to my 74HC595 Shift Register Board. The original version, even with its flaws, was used in the latest Light Show to help control 10 RGB LEDs. It worked out quite well but, again, it had its flaws. I’d love to have a revised board in my hand by the time I’m ready to go back to the Light Show.

sch1

This is the new schematic for the board. It includes a breakout of the Output Enable pin which gives you some PWM control. Using this pin will PWM all outputs over the two shift registers (16 outputs), so my idea is to chain three together so I can dedicate each board to a color (red, green, blue). Of course, it’s not as flexible as something like the TLC5940 which has 16 channels you can PWM individually, but it’s cheaper…

Anyways, if the application doesn’t need PWM, I added another ground pin next to the OE pin so you can just connect them together. When you do that, the outputs have no PWM control. The first version of the board had the OE pin already connected to ground in the schematic.

brd

Admittedly, my first PCBs were auto-routed as I was just getting acquainted with Eagle. I’m still learning but I managed to route this one manually. There seems to be a lot of technicalities on what you should and should not do when laying out a board but I don’t think my design is too much off what the auto router would have done. I tried the auto-router earlier and it did some really odd looking turns and loops around pads… Anyways, it’s just like solving a puzzle, though it takes me a few tries to get it right.

If you’re interested in buying these boards, let me know. I’m trying to decide on how many to get made.

Thanks for reading!

Attiny85 Programmer/Breakout Rev B3 Preview

Let’s go back to basics, shall we?preview1_frontI decided to throw out the whole breakaway section idea. It complicated things and there’s always the chance of a bad break. I put everything back on one board, which is now down to a 3x3cm footprint, 38% smaller than Rev A. The space savings come from less silkscreen text (removed the word “Pin” for the pin numbers) and using SMD components for the power LED indicator and resistor. I would have gone with an SMD capacitor but it costs more than the usual through-hole electrolytic capacitor, at least from where I get my components for these boards. With the price appearing to go up to get these boards manufactured, I’m looking for savings.

preview1_backAnother thing that changed with this sub-revision is that all of the pads are circles and are bigger than they have been on previous boards. They were kind of a pain to solder because any circular pads were really thin. I’m still working out the right size but I’m happy that I know  out how to address that issue now.

To date, the Attiny85 board was my most “Watched” item on eBay so I take that as an indicator of interest for this kind of thing so I’m set on getting these made. Being 3x3cm, I can’t fit two on one 5x5cm board which is what I have to work with to get manufactured. I’ll probably do something simple with the rest of the space but I want to nail down this one first. Thanks for reading!

Attiny85 Programmer/Breakout RevB2 Preview

A little while ago, I posted about some updates to my Attiny85 Programmer & Breakout PCB that showed off a new design with a breakaway Programming section of the board. I threw that out and started over again. There’s still some work to be done but I wanted to show where I’m going with this.

render_frontThis is a render of what the board looks like. The program I use to render places the design on a rectangle so keep in mind that the purple outline would be the edges of the board.

The Power In and Attiny85 have swapped places. I’m going with an SMT LED and resistor for the power indicator to open up some more room on the board (labels are in the design, won’t be printed on the board).

The board is designed so that the Program section would be broken off once you’re ready to use the the board as a breakout. What if you realize later on that there’s something wrong in your code? You could connect up your Uno using the Breakout section, but you’d still need another capacitor for the reset pin on the Uno, and this kind of defeats the purpose of the board. I’m working on an experimental idea to make it easier. The pads next to the Power In area is a temporary programming area where you’d connect the Program section. The problem is making the connections. You can’t really connect the Program section back directly using headers because then you have no way of making another set of connections to the Uno. The best way would be to make the connections on a breadboard. It’s not ideal, but it’s still easier than looking up which pins of the Attiny85 go where on the Uno.

render_backI’ll put a URL to an updated manual on the board again. I still want to get some instructions on the board with the space I have but the small size of the board makes it difficult to put anything really specific. I’m on the fence on whether the text on the Program side will stay (the lines it’s referring to are on the top side of the board, I need to add lines on the bottom side too).

I’ve been making an effort to getting the sizing of text (and traces) right since I made the text on my AMS1117 board a bit too small.  I use mm to design my board, but a lot of help resources and parts of Eagle use mils. I made a table of conversions between mils and mm. I put it up for download as a Word document and pdf in case you’re interested. I got the table from here but formatted it to print.schematicI redid the schematic, chopping it up into sections and adding labels. Everything was directly connected to each other in the first schematic. It was messy, but not having things directly connected to each other does worry me in case something isn’t connected properly. I’m constantly checking connections and working on the other details of the board I talked about above so I’m taking my time. There were people watching the Attiny85 Programmer and Breakout Rev A board on eBay so hopefully that means there is some legitimate interest in these boards. I would like to get them manufactured.

Just a note for people who are Googling around for the warning, “Segment of net [name] has no visual connection”, I deleted the label of that net and placed a new one to clear the error. I couldn’t find much help when I was searching around so hopefully people land here if they run into the same warning.

Anyways, thanks for reading!

AMS1117 + Atmega328p PCB update

combinedI’ve combined the two designs I was working on. The top is the Atmega328p breakout and the bottom is the ASM1117 voltage regulator that outputs 5v and 3.3v. I ordered some parts for this board as there is a sale on at Dipmicro. I’m excited to try SMT soldering with my iron. I need to do some last minute checks on the board to make sure the connections are correct. I’m also waiting for my first boards to come in so I can make adjustments based on those if necessary.

This board includes some things I don’t think I did right in my first PCB. The board has rounded corners, which is not really fixing a problem but it is something new I’m trying. I also went with a small tab between the two boards with some small drilled holes to help make the break a little easier. I’m not sure how the first boards are going to turn out but I’m fairly certain the slot I made in it is not going to be what I was hoping for. Anyways, the last thing is that I didn’t make the top and bottom layers that cover the board part of the ground plane. I’m not sure if that’s really a mistake or not but I know it does help manufacture the board faster (instead of scrapping off everything but the traces) and takes away some traces, as well as some good electrical side effects like helping with interference and noise.

I will be receiving the parts for the boards in this post so expect a mailbag post soon!

Eagle PCB Experiments: Regulator and ATmega328p

As I wait for my first PCBs to come in, I’ve been trying to keep busy in Eagle. As I said before, the first PCBs that come in will teach me a lot, mostly about sizing and spacing. I hope I’m not being mislead too much with the design blown up on my screen.

Anyways, I’ve been working on two designs that will fit on one 5x5cm board. These designs are meant to work together but will be separate, much like my first PCBs.

1The first design is a voltage regulator that will produce fixed 5v and 3.3v outputs. This design uses SMT parts to keep it small, instead of using LM7805 through-hole voltage regulators. I did do it a couple of times in college but we used actual solder paste (no stencil) and a toaster oven. I will have to use my soldering iron this time which may or may not turn out to be a complete disaster. We’ll see.

Quick note, it’s actually AMS1117. I keep mixing it those letters. It’s since been fixed on the board.1Anyways, the regulator is to be used with this ATmega328p breakout board. Using the same terminal block components for 5v out on the ASM1117 board and the Vin for the ATmega328p board, you could solder them together with a male/male header if you chose to use the regulator for the ATmega328p board. I kind of want to add 5v out pins on the ATmega328p breakout board but I want to keep it small. The space beside Vin is so the other half of the regular board has somewhere to go and possibly some text so I can’t really put it there. Again, we’ll see. These designs are still in the making and won’t be sent off until I can see how the first ones turned out.

Eagle experiment: 5×5 LED matrix

My first Eagle project has been manufactured and is on its way to me from China! I want to keep experimenting in Eagle so I decided to do a 5×5 LED matrix. I don’t think I’d actually get these manufactured. This board would be great for a multiplexing programming tutorial though.

2It’s perfect for a programming tutorial because the only “safe” way to program this board is by energizing one LED at a time. My theory is that if you use persistence of vision, where you flash a group of LEDs individually in fast succession, you’d only be drawing the current of that one LED so you’d never go over the maximum current rating of an Arduino pin (40mA). I may add in transistors later on, but I kind of want to avoid it in case I do get these manufactured and possibly get it all wrong…3This is the schematic. Pretty basic.

Be sure to come back on Saturday for the 1st year birthday of this blog! Thanks for visiting!