LED Binary Clock Design w/ Arduino - Page 1
Forum section: electronics / projects

author: PeteJM
author_rank: Contributor
timestamp: March 18, 2014, 11:37:54 pm
content: Well, critique please!Binary clock inspired byhttp://www.postcogito.org/Kiko/BcdClock.htmlKiko's BCDClockUpdated DC Jack to not have the circuit explode if the power is plugged in Center Negative (Design was also originally Center Neg)9v Battery Backup w/ a 9V-12V Wall Wart for DC Power (Center Positive on Jack)Atmel ATTINY84A-PU BasedAdded JTAG & Extra 6 Pin Breakout with Pos and Neg Supply w/ Protection DiodesPlease review and add to this or give me ideas for more if you likeAnd if you would like to purchase board, please PM me. If this design is sound and checks out I will be getting the boards made since it is my first completed design ever...

author: mariush
author_rank: Super Contributor
timestamp: March 19, 2014, 12:12:53 am
content: The way you arranged those leds in the pdf is very confusing. I'm not even going to try and understand if they're wired correctly.You don't need a 220uF 25v capacitor on the output of the 7805 .. a 47-100uF 10v is enough.1n4148 is overkill for that, you don't need high speed diodes for this project but if you have them already they're ok to use.You could use a single pchannel mosfet instead of two diodes for reverse voltage protection.Do you really need 20 Mhz for this project? Maybe you'd rather use an oscillator that would make your math easier?Using pb3 just for reset when you are multiplexing so much stuff there seems like a waste. You could just disconnect the 5v regulator for a second with a switch instead and use that for other things.

author: dannyf
author_rank: Super Contributor
timestamp: March 19, 2014, 12:22:00 am
content: QuoteHow much current draw do you think there is and how much current can a 1n4148 take?

author: edavid
author_rank: Super Contributor
timestamp: March 19, 2014, 01:08:00 am
content: 1. I greatly prefer 5 column sorta-BCD... but if I were making a 6 column clock, I'd add dummy LEDs for balance2. A plain crystal isn't very accurate, unless you do SW or HW calibration... I suggest counting line frequency, or using an RTC module3. Forget the weird modes, add reverse time adjust, and possibly hold

author: PeteJM
author_rank: Contributor
timestamp: March 19, 2014, 12:37:06 pm
content: Revised it a smidge, 16 MHz crystal, n-type mosfet for reverse voltage protection.

author: Kiko
author_rank: Newbie
timestamp: September 18, 2014, 06:19:15 pm
content: Hi PeteJM,Thanks for the update to the circuit and giving proper credit.Instead of the mosfet, why not a diode bridge so it works with both center positive and center negative power bricks?While you're at it, since you have pins left, why not put a buzzer so you we can make not only a BCD clock but also a BCD _alarm_ clock?Keep up the good work.

author: SirNick
author_rank: Frequent Contributor
timestamp: September 18, 2014, 07:25:58 pm
content: Neat project. I got one from Think Geek a few years back, before I learned digital electronics and realized it was something I could build myself.It's a good project to cut your teeth on.OK, so my biggest recommendation is to redo the schematic with a few simple but major design rules in mind:1) A schematic should first and foremost be easy to read. That's why you don't just post an image of the PCB and call it a day. Look at yours from a distance, or unfocus your eyes a little to blur the details. Can you tell what's going anymore? If it makes your eyes cross, redraw it. Use white space. We're not short on electrons, so don't be afraid to waste some virtual paper.2) Convention is to read left-to-right. Power on the left side, output toward the right. Break these rules if it adds clarity, but be skeptical of whether it really does.3) Similarly, convention is to have Vcc on the top, Gnd on the bottom. Having your rails mixed in with signals makes it super easy to mix things up. For that matter, you don't need Gnd lines, or even Vcc lines. Instead, you can use Gnd symbols and whatever your schematic program provides for power rails, like an upward arrow with the voltage next to it.4) Separate your components into logical blocks. Take the regulator block for example. Your power jack, polarity protection diode(s), regulator (reverse that left-to-right to accommodate the flow), bulk caps, etc.. all that goes in one logical section, and then you can just use a symbol that says "+5V" on the output side. Other places in your schematic that have a "+5V" symbol are understood to connect to this point.5) Your MCU is the octopus of this diagram, so be careful how you route lines around it. For e.g., the crystal stuff should be in a neat little block coming off one side, but kept away from other stuff to show it's an isolated block of parts. (Otherwise, it gets easy to mix up, e.g., the load caps for decoupling caps, or whatever.) Think clarity -- if it's a standalone block of parts, make it visually distinct. If you need to rearrange the pins on the MCU block to make the layout more convenient, go ahead and do so.6) Things like the reset switch might be best off to the side of the diagram, where you have some unused space. Provide the pull-up / pull-down resistor, and any other signal conditioning items, right there and take a single trace back to your MCU. Or, use a signal symbol like "Reset" on the output side, and a complementary "Reset" symbol on the pin of the MCU where it would connect.Not that I'm an expert at schematics, but I posted this one on another thread recently. Take a look and see if you can follow what's going on. It should be pretty clear, even if you don't know what the thing does, to see what the parts do.

author: Dave
author_rank: Super Contributor
timestamp: September 19, 2014, 12:34:55 am
content: SirNick, Q1 in your schematic is turned upside down. You need to swap drain and source to make it work properly.

author: SirNick
author_rank: Frequent Contributor
timestamp: September 19, 2014, 01:57:42 am
content: Aw man... thanks. Apparently I've been using that one backwards for a while. I'm accustomed to a different symbol, but that's the default in my schematic editor. Oh well, it's correct on the PCB at least.