Led Clock Feasibility - My first project

[IvanoArduino]

Hi guys and good morning all from a total newbie to this world. The aim of this post is to ask you guys if i'm going the right direction to master the knowledge to build my project.

To cut a long story short, my plan is to build a clock mixing the old style design of reclaimed pallets with a touch of modernity using LEDs to mark hours , minutes and seconds.

The aim is to keep all the lights ON once the given time has passed. To be clearer, if the minutes are "18" i would like all the previous leds (0 to 17) to be all on.

I'm pretty sure that the knowledge to build this resides in mastering Charlieplexing and Shift Registering (please correct me if i'm wrong). So at this point in time, i know what i have to "study" to give life to my project the way it's designed in my mind.

I've already seen some clocks working this way, hence i'm pretty sure it can be done (happy days!). Point is that i've only seen clocks where this design is achieved with only 1 row of leds. My aim is to swith on 4 rows at any Tn time. So, for the minutes, once it reaches 59, i should have 59 * 4 = 236 LEDs ON simultaneously (for the minutes only... plus N for the hours).

Can anyone point me to the right knowledge to be mastered to achieve this? I'm assuming is a problem of sustainable voltage (resistors, power supplies etc etc) leds in paralel/serial; multiple shift registers and so on so forth...

I'm attaching a small mock-up to be understandable on what i would like to achieve (it's based on the first 5 minutes of each hour). I've marked "Ok" the first row, meaning that since i've seen something similar, i'm confident in knowing what needs to be mastered to achieve that result. The "?" refers to what i haven't been able to understand if it's achievable or not (row 2, 3 and 4).

Would it be advisable to build a Matrix for each of the 4 row (with N 8-bit microcontroller such as SN74HC595, for each row) , or can be achieved with a "simple" 4 X 60 matrix?

Thanks a lot in advance to everyone "wasting" their time to give a helping hand!

Seeya!
Ivano

[Due_unto]

I'm not understanding completely the concept of how you are wanting to display the time other than you want 4 circles of 59 or 60 leds. From your description,when minutes = 1 the first led in each circle lights, at minute 2 the first leds stay lit and the 2nd set light up, all the way to minute 59. So for any given minute, m * 4 leds will be on. Where and how are you showing the hour? Are there going to be additional leds for that?
Do you always want all 4 leds for each minute to light up together or do you want additional control over each row (or circle)?

[saildude]

I doubt the SN74HC595 will turn on 8 LED's at the same time without toasting the chip. Ran into that issue with a project last year - you could use the SN74HC595 to drive a high power output chip - I want to say UNL2803 but would not bet much on my memory - then one output from the SN74HC595 could turn on 4 LED's at a time by driving the UNL2803.

There are some higher output expander shift register chips out there that might drive more than one LED per output if wired correctly.

You want to look at both the capacity of an individual output as well as the total capacity of the chip.

[anon57585045]

Well, one HT16K33 backpack board supports 128 LEDs, so two of them could do it handily. Convenient and dirt cheap. The matrixing will help keep the wiring under control too.

[wvmarle]

If four LEDs for every minute, all on/off together: place then in series.

Also I'd go with shift registers rather than charlieplexing or so. Makes it also much easier to wire up the required drivers for all those LEDs (don't even think of having the Arduino power them). If you want to control them all individual (every 15 seconds one more to light up) then the shift registers may be able to power each LED individually.

Start with a single shift register, get that working, before you move on to building the whole thing. That's a lot of soldering, you really want to be sure that you get it right the first time around.

[PaulRB]