Atmega328p Breakout PRO

The Atmega328p Breakout Board has been out of stock for a while. I have half of the new components in hand, and the PCBs have been shipped and are on their way. The rest of the components will be ordered in the next couple of days and, if it’s like the last time I ordered, it will arrive the next day. Friday is Good Friday so I have to keep that in mind, and hope that everything comes in by then. I’ve made the decision that I will no longer sell unassembled kits so I hope I can use this long weekend to put them together so I have a decent stock ready for the next week.

Anyways, while I’ve been waiting for the new batch, I’ve been working on something else…

draft1To the right is the first draft of the Atmega328p Breakout Pro. The current base version will likely drop the ISP header. The new Pro version will sport the ISP header, in addition to a voltage regulator circuit. As I talked about in the last post about voltage regulators, I’ve been using my AMS1117 voltage regulator boards with my Atmega328p Breakouts in my own projects. With the built in regulator on this Pro version, I won’t need that extra board. The regulator I’ll be using this time is the NCP1117.

I believe the NCP1117 is the same regulator as the one on the Uno, or at least similar. It can output a fixed 5v at 800mA, even though at 800mA it’s best to just use another supply if you’re driving things that need that much current. When I was learning about PLCs, I was taught to separate the power supplies between the control unit (the PLC) and the actual peripherals (sensors, indicator lamps, etc). I don’t see why that lesson can’t be applied to Arduinos, even if they draw less current than a PLC.

I’ve added in the reverse input voltage protection diode so the total drop out is roughly 2v, just like on the Arduino. You’ll need to supply it at least 7v to get the 5v, and I’d limit the input to 12v tops just because of heat dissipation.

I’ve been trying to find out if it’s acceptable to have an external voltage applied on the output of the regulator. I want to be able to apply an external supply to Vcc (the output of the regulator, and the input power supply of the microcontroller). That way, you could use a battery or supply that’s already in the operating voltage range of the Atmega328p (1.8-5.5v). I’ve been looking at some Arduino and Adafruit schematics and it looks like you can, if you consider USB Vcc as an external 5v supply. They have it connected to the same 5v net as the output of the regulator (although the Adafruit schematics use a different regulator). I’ll keep researching and probably put together a prototype demo circuit and see what happens.

That’s it for now! Thanks for reading and I hope you’ll stop by my Tindie store and pick up some of my Atmega328p Breakout Boards when they’re back in stock!

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Let’s talk regulators

IMG_20140918_193021As you probably know by now, I have released a few of my “old” circuit boards for sale on Tindie. Actually, they’re all revisions of previous boards I’ve shown off on the blog before. The one board you have not seen revised yet is my AMS1117 3.3&5v fixed voltage regulator board, pictured on the left. I’ve been looking over the design, while also straying away from it looking at other low drop out (LDO) regulators.

Functionality of the original board was not a problem. I still use these boards for prototyping and testing, and also in my final project builds like in my 24/7 powered ESP8266 project. The worst part of the board are the capacitors because they’re so close to everything else on the board including each other. I didn’t leave enough room between the larger capacitors so they’re awkwardly pressed up against each other. It’s so bad that I used hot glue to keep them solid in place because some of the capacitors aren’t sitting flat on the board. This can be easily fixed in the next revision by moving to SMD parts, which has been the plan for all of the boards since I decided to revise them all.

IMG_0767With the drop out voltage of the diode (reverse input voltage protection) and the regulator itself, you’re required to supply at least 7v to get 5v out of it. That’s the same thing as everyone’s favorite LM7805 which has a drop out of 7v, without a protection diode which would add another ~0.7v to the total drop out of your regulator. With that said, I pretty much only use 9v batteries with my AMS1117 board because it meets that minimum input voltage without being too much over. I have the ESP8266 project powered 24/7 so I’m obviously not using batteries but a 9v wall power supply.

spx1117circuit
SPX1117 schematic in Eagle – “Improved Ripple Rejection” circuit from datasheet

Speaking of wall power supplies, it introduces another “issue” if you use one with a voltage regulator. I don’t own a bench power supply or oscilloscope so I can’t get down into the fine details of  better monitored current draw or frequency response. You don’t have problems with frequency response with batteries because they output a solid DC voltage. However, with wall power supplies, the power from the wall is a rectified sine wave which is bound to have ripples in the output. I’ve been considering the change to the SPX1117 regulator which has a circuit in the datasheet to reduce the ripple… but then I wonder how much this actually matters to anyone. For hobbyist projects which is what these boards are made for, it’s really not going to have any major affects to it, as demonstrated in my projects that have worked well with the regulator board for extended periods of time.

I’m not really sure which regulator I’m going to go with. The main reason for looking at the SPX regulator is because they’re more readily available from my go-to suppliers than the AMS regulator. I may even just put the regulator circuit on the boards that would need them, like the ATmega328p breakout board. That’s the biggest motivation for designing these regulator board anyway. In that case, I probably wouldn’t need a regulator that can put out as much current (800mA)… We’ll see! Thanks for reading!

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!

Moving on

It’s kind of depressing when you think about it, but my ESP8266 project is held up by two little switches I need that are somewhere in the mail. It’s going to sit off to the side until those switches come, so I thought I’d shift gears and give you a quick preview of what’s coming up.

RF Transmitter and Receiver

IMG_0001I’ve never been much of a communications guy. Protocols and accommodating for noise and interference and all that has always been confusing/boring to me, but I seem to be tip-toeing toward it these days. I received two RF transmitter and receiver pairs in the mail today. I didn’t have a project idea in mind when I ordered them, but they’re so cheap that I figured it would be would be nice to have lying around if I did come up with something one day. I’m still drawing up a plan, though I think it’s only natural that I try to use that temperature sensor that was originally destined for the ESP8266 project. I haven’t done enough research to see what is and what is not doable with this pair so I can’t confirm anything just yet.

bbIn the ESP8266 project, I have three mini-breadboards that each have a main purpose on them: One for my AMS1117 power regulator, one with the sensors, and one with the ESP8266 module. I decided to try and combine two of them so I could free up one so I could use it to play with the RF pair. I managed to cram the AMS1117 and ESP8266 onto one mini-breadboard… As long as it still works, it’s fine. I hope that this project will be on a perfboard soon anyway.

74HC595 Shift Register Boards Rev B / Light Show 7

I hadn’t mentioned it before but I sent the next revision of my 74HC595 boards to get manufactured and they are on their way to me right now. I’m pretty excited to see how they turn out because they are my first manually routed board.

I’m also excited because it’s part of some upgrades I want done to the Light Show Project before I start programming a new show. These new shift register boards break out the Output Enable pin which allows for some PWM control. The backdrop will definitely have that, but I’m also considering having all LEDs in the project controlled by shift registers, including the fountain LEDs which have always been controlled directly from the Arduino. There are advantages and disadvantages to that but, either way, I plan on taking a close look at how everything is wired.

In addition to working on the wiring, I’m still looking for ways to make it even bigger. For every version of the show, I watch the show and pick out things that I want to focus on. What I realized with Light Show 7 is that it’s not designed very well to watch on a widescreen… We’ll see what comes of that.

 

Thanks for reading! Stay tuned for more!

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!

DIY LED Bargraph

I’m planning on revisiting my 74HC595 shift register boards in Eagle soon. One of the things I want to add in the next revision is a breakout to the Output Enable pin which allows you to have some PWM control. I never tried it before so I started setting it up to test it. I don’t have any larger breadboards available so I had to use a mini-breadboard. I didn’t like having to lay out the LEDs and resistors, especially on these smaller breadboards, so I put together a line of LEDs on a perfboard. I didn’t bother going on eBay to buy some of those LED bargraph DIPs because I bought a bunch of things on eBay over the holidays so I didn’t want to waste any more time or money.IMG_0001Anyways, here it is connected to a shift register. The PWM worked just fine, though I think it may have looked better on a different color.IMG_0003I already had this piece of perfboard sitting around so I’m pretty happy that the design is pretty optimized. Everything fits on the board without too much wasted space. The 8 pin female header leads to the anodes of each LED and the single female header on the right is connected to all of the cathodes of the LEDs.
IMG_0004Soldering didn’t go too smoothly because I need to find a better tip for my iron. The one I used was a conical tip which doesn’t transfer the heat very well. I have another tip with a flat edge, but the edge is too wide for my liking.

Anyways, that’s it for this quick show-and-tell. 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!