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RGB LED based 4" Digital Clock Circuit Diagram

Wajiduddaim

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Hi



I want to create RGB digital clock (segment height almost 4").

Any one here can tell me with LEDs drivers ICs are best?

If I use LED Strip, is that a good idea?
 

KlausST

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Hi,

all LED drivers are the best ... if they are what you are looking for.

usually it´s the other wa round:
* first you decide what you need. Requirements .. specifications..ideas..mandatory...nice to have....
* after this one can decide which driver suits your requirement and which one not. Usually by using selction guides.

Which LED strip? They all are different.

Klaus
 

Wajiduddaim

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Hi
Now I decided to use these LEDs

TOGIALED|TOGIALED TJ-S5050UG3W5TLCRGBDW-A5|Light Emitting Diodes (LED)|LCSC

According to Datasheet

Power Dissipation .... 308 mW
Forward Current(DC) ..
30 mA
Peak Forward Current . 100 mA

Reverse Voltage ...... 5 V

Typical Electrical
Forward Voltage VF (IF =20mA)

......... Min .... Typ .... Max

Green ... 2.8 .... 3.0 .... 3.4 V
Red ..... 1.8 .... 2.0 .... 2.4 V

Blue .... 2.8 .... 3.0 .... 3.4 V

Forward Voltage VF (IF =30mA)
White ... 2.8 .... 3.0 .... 3.4 V

Reverse Current IR VR =5V --- --- 2 μA


One LED Max 100 mA and 6 LEDs on one Segment to Max mA is (100 * 6) 600 mA

and one Digit = 7 Segments = 600 * 7 = 4200 mA = 4.2 Amps

Is this calculation is correct ?
 
Last edited:

KlausST

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Hi,

100mA are for 10% max duty cycle with a pulse width of >0.1ms.
--> Do you want to pulse the LEDs this way?

If not, you need to calculate with DC current.

and there will not be all colors of one package fully ON?
I´d limit the overall LED package current (for all leds combined) to 30mA, maybe 50mA.

if there are 6 LEDs per segment and you want all the LED(pacakes) of this segment to have the same color, then you may connect 3 (x2) or 6 LEDs in series.
Then you need 6 x 3.4V =20.4V max LED voltage.

Klaus
 

Wajiduddaim

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clock.png


I want to use this method first segment data, and then its color (for example 'R') then then 2nd segment then "R" and so on.....

max 1 or two color glow same time (R, G, B, RG, RB, GB, Or White), so max 7 colors

RGB all three and RGBW all 4 color will not glow

common Anode OR Common Cathode are not problem
 

KlausST

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Hi,

Thanks for answering my questions ;-)

Now there are just 5 LEDs in vertical segments. Didn't you say 6? How to treat them?

4 digits, 7 segments, 4 color.

Do all the segments have same color, or do you want to control the color of each segment iduvidually?

*****
Usually one wants to keep multiplexing rate low. For a clock 4 digits x 7 segments --> 1:4 rate = one digit per time slot.
4 idividual digit controls, only one ON per time
7 individual segment controls, 0..7 ON as desired.

Lowest wiring may be to use 4 digits x 4 colors = 16 lines plus 7 segment lines gives 23 lines in total.
You may reduce
* 4 digits to 2 biniary digit controls
* 4 color controls to 3 binary color controls
Give 5 total digit/color controls instead of 16.
Saving 11 controller port pins.

I don't know whther there are ready to buy 4 digit 4 color 7 segment controller ICs.
You have to do a search on your own. Use the selection tools of a distributor internet site.

There may be 8 x 8 color LED matrix controllers.

As alternative you may use the digitally controlled color LEDs.

You are not the first one with this idea, thus I'm sure there are example circuits in the internet. Did you do a search?

Klaus
 

schmitt trigger

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Are you familiar with I2C?
There are many multi channel I2C LED drivers with added functions like PWM.

I have used devices from NXP, but many others offer them too
 

Wajiduddaim

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KlausST

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Hi,

did you read the neoopixel datasheet?
I guess there are application notes and many design examples. Go through them.

Klaus
 

Wajiduddaim

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I was reading the datasheet of WS2813 RGB LED and i found

1) Recommended application circuit diagram:

7 seg sketch edaboard.png

Note: R1 is the protection resistance of the IC, which has the function of preventing power spikes and anti-reverse connection. The general value is 150R~390R. C1 is an external filter capacitor. One The general value is around 100NF.

2) Another Option :
Because WS2813 has built-in resistors and capacitors, the following circuit diagrams can be used to save wiring space for more complicated PCB wiring:
7 seg sketch edaboard 2.png

I am Confuse, If WS2813 has built-in resistors and capacitors, then why the upper is recommended, i mean what is extra benefit for upper circuit-diagram.
Will the result be same for both circuits????
 

BradtheRad

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The extra resistor & cap could be included in case you discover a need for extra filtering, in case the 5V wire has spikes and noise on it (due to devices switching On-Off, etc.).
The resistor provides a measure of isolation, giving the capacitor extra filtering effect at the terminal.

Perhaps the author found that it's needed so he included it. Perhaps someone else found that it's not so he omitted it.
 

    Wajiduddaim

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