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# Led Clock Feasibility - my first arduino project Answered

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

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## 1 Replies

Downunder35m (author)2017-11-30

Comes down to how much your matrix can handle in terms of current.
You might have to use a transistor for each block of 4 LED's.