DIY Digital Clock: Take 2!

What time is it?

Time to make a new clock!

About a year ago, I designed and assembled my own custom made clock. You couldn’t say it was in an enclosure since its guts were spilled out on both sides of a piece of foam core. I felt like, a year later, it was time to redo it and put it into a proper enclosure.

So, what time is it? Time to build us a new clock!

The Guts

1

I tend to get carried away and too focused to take proper progress pictures. This is literally the first picture I have from the electronics part.

Soldering all of those LEDs and components took a full day. I used hot glue to try to keep multiple wires in place to solder as fast as I could but it didn’t do the best job to hold them in. At time, the glue would fall away from the PCB. Still, it’s better than fiddling with one wire at a time.

The only difference from the prototype build is a lower resistor value for the LED resistors.

Putting Together a Box

2

Foam core is a favorite in my “lab”. It’s all I use these days because all it takes is a knife to cut and it’s inexpensive and accessible (Dollarama rocks). I built a simple black box with a white cover place. I was hoping with a lower resistor value on the LEDs, they’d be able to shine through the white foam core.

3

With the soldered parts and the enclosure ready, it was time to put it all together.

4

I glued a piece of foam core behind the control board to isolate the connections on the back with the display connections. I ended up mounting the two display panels on it’s own piece of foam core anyway so I guess that wasn’t really necessary. The display foam core backing fits tight with no need for pin or glues to hold it in place.

5

The white foam core was still too think for the LEDs so I ended up going back to a plain white sheet of paper. It’s not noticeably brighter than the original prototype with the paper.  The piece of paper is held up by two strips of foam core on either side.

I didn’t like the look of it at this point but it was the end of the weekend so I left it for now.

6

I still like how sleek the black foam core looks, even with a few imperfections here and there from a not-so-sharp knife.

7

After a few days to think about it, I realized simply turning around my diffusing screen pulled the look together.

8

Time to pull the plug on the prototype and enjoy something new.

Thanks for reading!

NCP1117 Board Load Test (Part 1)

I’ve always wanted to push my voltage regulator board to its limits. The easiest way I figure is to get some low value power resistors to draw “high” amounts of current from the regulator board. I happened to pass by a local electronics supplies store today so I picked up a couple of power resistors, as well as some test leads and a flush wire cutter.

As a side note, I was actually looking for some test leads that have that wire hook thing but they didn’t have any that I liked. I didn’t own any test cables so I’m glad I picked up these alligator-to-alligator test cables. They were an impulse buy on the way to the cash register, where the cashier commented that he personally liked them. They are actually quite nice, though I find them a bit slippery when trying to squeeze open the clips.

Anyways, lets look at how the test went.IMG_20150628_163532 (1)It was a pretty simple setup, especially with the help of my new test leads. I connected the resistor between the +5v and ground output terminals of the regulator board. I had my multimeter in series with the resistor to measure the current. I used a 9v power supply to power the board.

One of the resistors is a 5-ohm 22-watt resistor. It pulled 880mA from the board. The other resistor, which is connected in the picture above, is a 6.8-ohm 5-watt resistor. It pulled 650mA from the board. Both tests caused the thermal overload protection to kick in. In under 15 seconds with both loads, I could hear a buzzing noise coming from the board and see that the current was dropping. The current dropped rapidly to about 350mA where it slowed its pace dropping down, about a mA per second. I didn’t want to leave it for too long so I pulled the plug around this point.

Blowing on the board to attempt to cool it off brought the current back up. I always thought that the thermal overload protection would act like a switch where you’d get no current at all from it, but it looks as though it doesn’t work quite like that.

Linear voltage regulators can be trickier than they seem, at least if you plan on pulling good amounts of current from one. It’s a good idea to expect that your linear regulator will get hot (that’s how they work anyway, it’s sometimes hard to appreciate it with low current projects producing negligible heat) so consider heat sinks and ventilation.


To update those who actually follow along with new posts, I got a job earlier this month (not electronics related, unfortunately). While I don’t have as much time as I did before to work on my projects, the income does allow me to buy more things for my experiments. Coming in next week is a new bench power supply which should make this load test experiment more interesting with different input voltages and current readings from the source power supply. I’m excited.

I also updated my Atmega328p Breakout Board and am waiting for those PCBs.

I hope I can start posting more again as I adjust to things. Stay tuned and thanks for reading!

Where are my LEDs?

I haven’t done any work on the old Light Show for a while because I’ve been waiting for some WS2812B LED modules from an eBay seller in China. It’s been so long that I’m thinking of just making my own WS2812B modules. I was hesitant about doing that in the first place since I’ve never used these LEDs before, but, besides the cost, there’s not many reasons why I shouldn’t try. I can get the WS2812B LEDs and capacitors from a local (well, within the province) supplier and the PCBs take about two weeks to manufacture and get here if I pay for fast shipping…

Thanks to the popularity of these LEDs, it’s not hard to find the resources I need. I’d like to try other PCB layouts in addition to the simple single LED board. I think this could turn out to be a really fun project! I will have more to share on this when I get a little more of it completed.

While we’re still on the topic of the Light Show, a few other parts came in for some upgrades. I purchased 5 more pumps which look better than the original pumps. My intention was to have them as spares to replace any of the pumps that don’t perform well, but now I’m considering expanding the number of fountains. The main challenge with that is finding or building a larger pool since the current container is too small for that. I also got some new mosfets in so I can redo the circuit for the pumps. I’ll have to decide how many pumps I’m going to be working with before I get to that…

As a side note, a new PCB design of mine should be here by the end of the week so stay tuned for that as well!

Updating the regulator

I don’t have a bench power supply so I rely on wall plugs that already regulate the voltage level, sometimes combining it with a regulator circuit/IC to drop it even further. In the beginning, I used to whip up a classic 7805 circuit on a breadboard. These days, I’ve been using a low drop out regulator circuit on a custom PCB. I’ve been using my AMS1117 regulator board for a long time now in projects and prototype testing on a regular basis. It’s clunky and one of my first PCB projects ever. It’s about time it got an update.

IMG_0001It’s been a design I was sitting on for a while. It uses all surface mount components, which I picked up in my last Digikey order and had laying around for a while.

IMG_0002Instead of the AMS1117 regulator, the new board uses an NCP1117 regulator, although the actual IC says RBK117 for some reason. My initial test impressed me as I got a perfect 5.00v on my multimeter. The AMS1117 regulator would usually measure to be +-20mV from 5v. It may end up varying with age but in any case I’m happy that it works. I dropped the 3.3v regulator since I never really used it, except for in the ESP8266 project.

I’m very excited to start using this smaller, neater looking board regularly. I still have a bunch of those bulking AMS1117 boards so I’m not really sure what to do with them now…

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!

And now for something new! (Store blog category)

The blog’s viewship has already surpassed January, so we’re on our way to getting back to how it was at the old blog. This is mostly thanks to my ESP8266 project. I feel like I’ve been neglecting the blog because I haven’t had much to talk about in terms of new Arduino projects… That’s why I’m here to start a new blog category called Store, which will give you some insight on how my experience selling my products online is like, which is what has been taking up all of my time. Sorry if you’re not into big walls of text, but I hope to include pictures where ever I can.

Not too long ago, I decided to take designing circuit boards more seriously so I could start an online store. Since then, I’ve listed some of these boards on Tindie, as well as some used parts from my PLC trainer on eBay. The money raised by the sales on eBay is going directly toward the development of a couple products that will be hitting Tindie in the coming weeks. Planning it all, even though it doesn’t seem like a lot, has taken up a lot of my time, which is why all of my Arduino projects have taken a backseat.

I’ve raised just enough money so far to cover the costs of doing a relatively small run of some new boards. They are the second revisions of my Attiny85 Programmer and Breakout board, and my Atmega328p Breakout Board. They both got some important changes. They’re both manually routed and include a power LED indicator. They also include ISP headers for advanced users with their fancy 6-pin ISP cables (but you can still use jumper wires). Most of the components have changed to SMD.

alone

The Atmega328p Breakout now breaks out the Reset pin where you can easily add in an external button. It covers two pads so you basically want to short the connection, using a button or switch, to reset the microcontroller. It’s slightly more friendly than the single Reset pin like on the Arduino.

Like I said before, the boards are also getting power indicator LEDs and ISP headers, which you can see in the top left corner of the board. Originally, I left that area open because my AMS1117 voltage regulator was supposed to line up with the input power pins of this board but it didn’t work out right.

alone

The Attiny85 Programmer & Breakout sticks to its roots as being a simple-to-use programmer, so it still includes a section that tells you what pins to connect to the Arduino, in addition the new ISP header. The size is also much smaller and is designed to fit into a breadboard (830 point, and similar) where the input power pins fit into the power rails of the breadboard, and the Program and Breakout pins fit into the prototyping area of the breadboard. The ISP header is typically sticking out from the top so it shouldn’t interfere with this plan.

That’s it for now! These boards should be ready sometime near the middle or end of March. Fingers crossed it all goes well!

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!