I can't wait to see this thing when you're finished. What kind of case do you plan on? I was thinking something a nice smooth and white shell, with a smoked plexi front... Inspiration: http://plusminuszero.jp/collection/ad03_8intv.html
Never thought about it (too much thinking on the electronic part actually...) Knowing myself it will be anodized aluminum for the casing and blue plexiglass in front of the displays. The plexi is really needed as without it the contrast of the displays is too low and almost unreadable in daylight conditions (and blue to minimize the light losses through the plexi). CD
Loving the results of the LED clock design. I also want one! And have ordered 1" Blue LEDs. I do however want to use the AVR microcontroller, as I can program it in Basic (BASCOM Basic) Some months ago I thought up a design where I had to make all the little acrylic pieces my self ("|" x 7 x 4). This would however have High Bright Blue LEDs.... but then I started to make the digit parts, and that was just TOO MUCH WORK. Love the fact that you can buy the finished LEDs. Hmm... maybe if I were to grind off the back of these pre-facbricated LEDs and add High Bright Blue LEDs behind the numbers. Yes, that might just work. And as I have had to order 10 x double LEDs there should be some to work with. Oh, how I love Modding!!!! Keep up the good and inspiring work. Well, another design difference is that I also want to control the clock through a serial port, and can thus create a design without all the buttons and all the other fancy stuff you have in your design. Your design IS however a COMPLETE LED clock. Finally, I am probably not going to need all 10 double digit LEDs, so if anyone wants some (at cost) please email me. Turbokeu, if you end up having some blue acrylic left over, I would like to buy a piece. Alvin
I don't think you can just grind off the back of one of these, and pop a new led in. I think the LEDs are set in some sort of resin or something.
Thanks... I just tried my single 0.56" and dual 1" blue displays with a 390 Ohm resistor on a 12VDC voltage (resulting in 22mA segment current at Uf=3.4V). God they are bright! The color is a diffused deep blue and the segment surface is very equally lit. I'm really curious how bright will be the 4" displays (four LEDs/segment)... However, the connection diagram of the dual displays on LC LED's website is wrong: The display has 10 pins (not 18), the segments pins of both digits are common but there are two separate anode pins (one for each digit), meaning that the dual displays can only be used multiplexed (not a problem since this is what I planned to do anyway). That's why I bought 12 pieces of them: I can build four clocks (all four are presold to family and friends)... I will have to buy new sheets of 3mm thick blue acrylic, so no problem if you want some. Made some paper drawings too for a 6-digit display with the 4" displays (they should arrive very shortly). OMG, it's huge!!! The 4" display housings are 122mm (4.8") high and 90mm (3.54") wide (digit is 4.0"x1.5"), meaning that a 6-digit display will be at least 54cm (21.3") wide (not counting some space between HH and MM, and MM and SS) !!! Luckily I found 60cm (23.6") wide PCB board. This will be a beast... CD PS: If you want big digits I advise the 2.3" ones... I will post some pics of the 4" displays as soon they arrive.
My word, seems like you are starting a small Clock factory there. Have you thought of a name for it yet? Ledlex? Glad to hear it, as I really want to be able to read this clock even in bright daylight. By the way, when I was talking about using different LEDs (read: more powerfull LEDs), I had no plans of completely replaceing the LEDs. I wanted to re-use the blue plastic top of the 7-Seg LEDs as well as that square base (resin) they are embbeded into, and then just shine through it from the buttom. Anyway, we'll see if it will be necessary for me to tryout this mod, or the standard 7-Seg will do the job. Keep on clocking! Alvin
When I start something I do it right! Seriously, lots of people around me would like a blue LED clock (four 1" clocks are already sold before I even started to make them). Will surely order twelve 2.3" displays as soon the're in stock again... And honestly, I didn't even think about a name yet... All (and especially multiplexed) LED displays suffer from contrast issues in direct day- or sunlight. The best cure to this is a monochrome filter in front of them (transparent acrylic of the same color as the displays). Contrast is therefore increased by a factor 2 to 5 (I experienced this several times!). At 22mA DC the segments are REALLY bright (about 48mcd following the specs). What bothers me more is how the luminosity will be when multiplexed at 16.6% (Duty Cycle of 1/6 sec) for a 6-digit display. Max specs are rated for 100mA at a duty cycle of 1/10 and an ON time of 0.1msec (I will try with about 50mA for 1/6th of a sec). CD
Yes, I have been thinking about this as well, and had decided to just add another MCU or more I/O pins. Though if it is enough, the way of short powerbursts is much smarter, as it requires no extra components, and achieves the same light results. I see that your design will be really good. About my extra wish, with a Serial hookup, would the PIC be able to handle that? It seems to me that there are still a few pins avilable on the schematic. Looking forward to seeing some pictures when you get one of the clock's built. Alvin
A 16F877 has 32 I/O pins (a 18F448 or 458 has even 33 I/O's), non multiplexed you would need 6x4=24 I/O pins when using six 4543 BCD to 7-segment driver/decoders to drive the digits directly. Still feasable but the total current draw of the six digits would be seriously increased (worst case about 6x7x20mA=840mA as opposed to about 7x50mA when multiplexed). Lots of PIC µ-controllers like the PIC16F876 have an embedded USART on pins RC6 (TX) and RC7 (RX) which can be simply used as a asynchronous RS-232 connection. Would just have to relocate actual connections to RC6-RC7 to other I/O pins in the schematic. A design is never really finished... Between these schematics and the final design lots of things can still change, as I/O pin assignments may be modified for an easier PCB routing or easier coding for example. Doesn't really matter since port pin assignments are made in the very beginning of the code. CD
Found a way to not multiplex the displays AND to use only 4+3 = 7 I/O pins. Unfortunately it requires one (cheap) 4543 BCD to 7-segment decoder and one (cheap) ULN2003 driver per digit. Four I/O lines are used to output the BCD code in parallel to each 4543, and three I/O lines for the digit selection (also in BCD format) through a 4028 4-to-10-decoder which outputs are then fed into the LD (Latch Disable) inputs of the 4543's. That way each digit displays continously the latest value until a latch pulse is applied which makes then a new value to be stored into the latch. The result is that the 4543's are multiplexed, not the digits, and therefore the displays are always lit (resulting in a higher luminosity). As mentionned before the total power draw is about six times higher than when multiplexing the displays (calculations in the schematic are done for 4" blue displays). (Click image for PDF file)
Yessssss !!!! The postman finally delivered my 4" (101.2mm) displays from LC LED Inc. today and I found the package on my frontdoor when I came back from work... Big package... Opening carefully... Examining the included invoice...: us$7.85/digit and us$4.95 postage (there are us$14.50 worth on stamps on the package...), for a total of us$52.29, not bad And then......OMG, OMG, OMFG...they are HUGE !!!! On the left: one of my LC-LED 0.56" (14mm) displays In the middle: one of my LC-LED 1" (25.4mm) dual displays And on the right, tadaaaaa, one of the LC-LED 4" displays... Display enclosure is actually 4.8" (122mm) tall, and every digit is protected by a removable adhesive protecting layer on the front side: View of the back side: Each segment (A to G) is lighted by five blue LEDs in series (Uf=16.25V @ 20mA), the decimal point is lighted by one blue LED (Uf=3.45V @ 20mA). These values are measured with a Fluke multimeter while power was applied with a variable lab power supply through a 150 Ohm resistor. The specs from the LC LED website are wrong as they state 2x4 LEDs per segment, as well as the decimal point... Anyway they are bright... Make me think that I will need at least a +20V voltage to drive those displays... Picture with the 0.56", 1" and 4" displays in my hand: The six displays together: a gap of 4cm between HH and MM, and between MM and SS as separation is shown. Total width of the 6-digit display is 64cm (25") meaning that the final LED Clock will be about 30" wide... Now wondering how to make a PCB that wide... Last picture with a CD and my watch for comparison: Will post pictures with the different displays fully (the seven segments) powered and lit ASAP... CD
Good job. Have you however made any tests to see if it is really necessary to add all of those extra chips? I mean, your idea about using power bursts seem like a good idea as well. Alvin
Not at all... I'll probably stick with the multiplexed displays, but the "continously-ON displays" were meant for you... CD
And I thank you very much for the effort. It's nice to know that both solutions are avaialble and has been give some thought. Alvin
Well, maybe it is not worth using a big PCB, maybe some other plate to hold the LEDs, and then wires to a smaller PCB, you may even have sockets at the small PCB so it would be easy to replace/change the LEDs. Just a thought. Alvin
Wow man, when I started this thread, I had no idea it would spark such a huge fire! Now Turbokeu has gotten into the clock manufacturing business, and has began stocking 7-Segment LEDs in his house.... Turbokeu, I am very serious about purchasing one of these beasts once you have a final design knocked out. You etch your own PCBs right? Also, I'm not sure if this is part of the current schematic, but will your final design be settable but the common hour/minute buttons we see on consumer alarm clocks? Looks very sweet so far, I cannot wait until you finish the design! Please, add this project to your site so that anyone using google can find a blue clock! P.S. Do you have to change any resistors to use different size displays? Or is it basically just a swap to switch from less than an inch to 4 inches?
