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!

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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.

My first attempt at Eagle

I never have things manufactured custom for my projects. It’s all put together using my own two hands. I haven’t had any good projects on deck for a while and I wanted to learn something new so I ended up with some motivation to try and pick up Eagle. I used it just once in college. I tried several times on my own after but I never took it seriously so it never went anywhere. Yesterday I sat through a YouTube tutorial series (Here’s Part 1) that guided me through it. I understand a lot more about Eagle than I ever have.

With the tutorial complete, I wanted to make my own design. I wanted it to be a revisit of a circuit I had done before so I have a good understanding of the circuit, and also something practical since I’d probably end up with 10 of these if and when I get them manufactured. In the end, I chose to redo the Attiny85 programmer shield I made a while back. It won’t be a shield that sits on top of the Arduino but it will still make programming easy and will break out the pins so I don’t have to keep looking it up.

schematicThe schematic is kind of a mess but I think it’s all good. I’ll need to take a non-lazy final look through it before I finalize any PCB layout.pcbThis is what it looks like at the time of this post. Things are bound to change though. I literally just added the Power On LED and resistor (R) because I had that space left. I’m a little skeptical this is the right size for a 5cmx5cm board because it seems like I’ve fit so much on it…3dI’ve been looking at different gerber file viewers and I came across ZofzPCB which renders the board in 3D. It’s pretty cool to look at since I have yet to have a PCB manufactured.  I tried a few normal 3D gerber viewers and my favorite is ViewMate. One thing that viewers made me realize is that I had to use vector fonts because the default font would show up bigger in the viewer and trail off of the board. It did not appear like this in Eagle so I learned the importance of checking it in a viewer.

Once I send it off to be manufactured, I’ll post up all of the files. Thanks for reading!