I am wanting to build a fairly large 4 digit 7 segment display. I am going to show time on said display. I am using an LED strip that has a plus and minus wire, no signal or RGB wire. How would I wire such a diagram. I can't find it anywhere I would really appreciate some help and maybe a wiring diagram. The less wires I have to connect to my arduino Uno the better. Thanks!
A two wire LED strip has an anode and a cathode, just like a single LED has.
"a fairly large"
What does that mean.
Large displays are usually made with TPIC6B595 shift register chips, one per digit.
They can be daisy-chained, so you only need three Arduino pins to drive a bunch of them.
Post a link to the LED strip you want to use, and tell us the length and/or how many LEDs per segment.
I am wanting to build a fairly large 4 digit 7 segment display.
Your requirement is a very broad question as “fairly large” has no real world measurement.
It may be quite a challenge if , as it seems, you are unfamiliar with such things in general.
It would be possible to get a discrete IC diagram or perhaps kit or even commercially made unit and modify the output to drive, say mosfets in place of the small LED’s and then use the mosfets to drive your LED strips.
You would need 7 LED strips per digit plus a few LED’s for the two “:” symbols assuming hours:minutes:seconds.
An Arduino clock someone built is shown below but no idea if it works or not.
You might be able to adapt to suit your needs.
Google search is the best place to start for unusual projects. Most times, someone has already done it.
Ok so after more mind bogling research (arduino always manages to make me feel like a moron) I have found a project very similar to what i want to do.
Ok so some of the features that this clock has such as wifi i won't be needing. I am planning on using this clock module:
I am going to use this LED strip:
So do i need a module to drive this and make it work or do I just need to solder all the wires together as done in the video? If so how do I up the power from 5v to 12v (is that even possible or do i need to drive it from a battery)? If so would I just connect the signal wire to my uno or...
30 LEDs per meter is a low density strip. You can only cut that 12volt strip in 10cm sections.
So minimum digit height with this strip is 20cm (~8"), with large (dark) gaps between the LEDs.
There are also 60LED/m strips.
Or 12volt long/thin COB LEDs the size of a segment.
Or large 7-segment digits.
So again, how big is this going to be.
With and ESP8266/WiFi, you don't need a RTC module.
A RTC module, even when accurate, is a pain twice a year.
Actually 8" is about what I am going for. The only reason I am going to use the RTC module is because I already have one and I barely have any money right now so I can't spend it on Arduino.
I barely have any money right now so I can't spend it on Arduino.
Then make a full plan.
You could spend more money on the drivers than on the LEDs if you start off wrong.
More expensive addressable RGB LEDs could be a cheaper solution overall.
It looked like in the video he didn't use any drivers. Is that at all possible doing it the way he did?
WS2812B RGB LEDs do not need a hardware driver, just a data signal from the Arduino and a big power supply.
The software driver often used is the Adafruit Neopixel library, or the FastLed.h library.
Awesome! That save me both time and money. So basically to be able to build this digital clock all I need is an Uno, the LED's, LOTS of soldering, and the clock module? I would assume to not over-amp the board I would need a resistor on the positive wire of the LED's right? You said a power supply, do you mean like an actual computer power supply or could I just attach the LED's to the positive and negative pins of the boared?
You can't "over-amp" the board unless you use too high of a voltage supply.
A 5V Arduino will only draw the amps it needs, either from 5V/1A supply, or 5V/10A supply.
The WS2812Bs will need a lot of current - up to 60mA per LED at full bright white.
The Arduino cannot supply that for more than ~ 10 LEDs if 7.5V is supplied at the barrel jack. Even fewer if 12V is being used, the 5V regulator overheats and shuts down. Same for USB, there is a 500mA resettable fuse that limits current coming into the USB connector.
Count up how many LEDs you are using, multiply by 0.06, and find a power supply that can supply at least that much.
The maker of the video seems to have under-estimated current draw.
Powering 86 addressable LEDs to full white could require 86*0.06A = ~5Amp
Using a single colour reduces that to 1/3, and using not all segment reduces that further.
But that still could be too much for common 500mA USB.
So if I am understanding correctly this is how it would work. I would connect the positive and negative sides of the LED strip to this power supply
The signal wire would go into one of the Uno ports (would it be one of the analog ports or one of the PWM ports)?
The clock module would obviously plug into the Uno also.
With this setup is their any way to change colors or brightness? Would this even work? I figured that 30(the amount of segments) times 0.06A=1.8A so I could easily use two LED's per segment which I think would make it bright enough.
I would use a minimum of three LEDs per segment.
Addressable LEDs can be brightness controlled in software, and/or a limit can be set in setup().
That also reduces average current draw.
Wise to add a ~330 ohm resistor in series with the data line, close to the first pixel of the strip.
And a 470 or 1000uF capacitor across the supply of the first pixel.
Plenty of examples for this on this forum.
Likely the wrong supply.
You need a 5volt supply for most addressable LED strips, not 12volt.
Unless you buy a 12volt addressable strip (less common).
Ok I think I finally have it...
Here is the wiring schematic (in words). 5V Wall wart powers Arduino via a audio Jack. This power supplies positive and negative will go to the positive and negative of the capacitor (obviously it doesn't actually matter but whatever I decide is + and -). Before the negative wire hits the capacitor it will have a 330ohm resistor (or does that go on the data line before the first LED?). Does everything there sound right? What size wire should I use? I was thinking maybe 16 gauge ish? Thanks!
Two LEDs per segment, and a 60/m dense strip?
Not going to be a very big display then.
You only need ONE cap.
The DC socket of an UNO needs 7-12volt.
The 330 ohm resistor goes INLINE with the data wire.
16-gauge (1.5mm²) seems impossible to solder to the LED strip.
Because of the more dense strip I am planning on doing maybe 3 or 4 per segment and upping to a 10A power supply. Does the capacitor just go on the positive wire? I will be supplying the DC socket with power from a wall wart I have that is meant for the Uno. As far as the wires what gauge would you reccomend?
Better buy a five-metre strip then.
You can find Fritzing connection pictures in many WS2812B threads on this forum.
Wise to read a bunch of them.
AWG18 sound about right, depending on your soldering skills.
Could also power the strip at both ends.
Capacitor connects to + and - on the strip (polarity matters).
Suppose the cap can be omitted if the wiring between supply and first pixel is short (< 30cm).
So why is the 5v Power Supply attached to the Uno's 5v and ground? I was planning on power the board from the audio jack style cable and then attaching the LED's to a 5v 10A power supply. I will probably omit a capacitor as the wire will most likely be very very short. How would I power the strip at both ends? Would I simply solder two wires to the + and - of the PSU and then run each to each end? If so would the data wire still only attach to one side?