Christmas lights....yay!

Projects General Guidance
1

I have a new mega board that arrived in the mail to day. along with a big box of simple standard LED lights.

https://www.ebay.com/itm/500pcs-Assortment-5mm-LED-Light-Emitting-Diodes-White-Yellow-Red-Blue-Green-Kit/153292238230?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

with my new knowledge of arduino i'm hoping to finally surpass the neighbors display this year. hehe

here is my thought...

i would like to wire an 8 by 8 matrix of leds. this would give me 64 individually controlled "points" i can control with my board. then i would intend to connect several LEDs in parallel to each individually controlled "point" on the matrix grid. i have wired small LED matrixs before and i am familiar with the necessary programming. My electronics knowledge is far behind my programming knowledge.

so here is my question...................................

If i bypass my mega's voltage regulator and supply 5 volts to its five volts pin with a big regulated power sourse, is there still a limit to how many leds I can power with the pins?

aside from the basic matrix wiring pattern
i have no clue what kind of kind of curcut i would need if a couple hundred or so leds surpass the power limits of the bourd.

would the power consumption be a problem?

if so could i use transistors to "gate" the power from an external sourse? 16 tansistors for each pin?
what kind of transistors would i use?

would i need some sort of resistors in my curcut? where would i put them?

2

The current that each pin can safely supply is ~20mA.

You can feed external +5v into the Arduino 5v pin but this will not make the Arduino more powerful.

Suggest you use Neopixels for this project.

Strings come in 144, 60 and 30 pixels per meter.

You can also buy individual pixels.

Cut a Neopixel string into 8 pixel lengths then arrange them into 8 rows.

Wire the 8 strings in series again.

Only one Arduino pin will be need to send data to your matrix.

Use an external 5v power supply to power the string.

Each pixel can be controlled individually and colours can be up to ~ 65000 different.

800×469 135 KB

3

taterking:
I have a new mega board that arrived in the mail to day. along with a big box of simple standard LED lights.
https://www.ebay.com/itm/500pcs-Assortment-5mm-LED-Light-Emitting-Diodes-White-Yellow-Red-Blue-Green-Kit/153292238230

Link corrected. I bought a pack of those for my granddaughter, but don't expect her to make use of them easily. I figure you will be mightily challenged too! :grinning:

taterking:
with my new knowledge of Arduino I'm hoping to finally surpass the neighbors display this year. hehe

Maybe, but don't bet on it if their name is Holdman!

taterking:
i would like to wire an 8 by 8 matrix of LEDs. this would give me 64 individually controlled "points" i can control with my board.

But not direcly.

taterking:
then i would intend to connect several LEDs in parallel to each individually controlled "point" on the matrix grid.

Not a good idea!

taterking:
I have wired small LED matrixs before and i am familiar with the necessary programming. My electronics knowledge is far behind my programming knowledge.

OK. If you were wiring them directly to the Arduino, then you have big problems.

taterking:
If i bypass my mega's voltage regulator and supply 5 volts to its five volts pin with a big regulated power source, is there still a limit to how many LEDs I can power with the pins?

There sure is! You should never be using the on-board voltage regulator anyway if you want to connect stuff to the Arduino. It is OK to power the microcontroller itself and maybe half a dozen LEDs at less than 20 mA each.

taterking:
aside from the basic matrix wiring pattern i have no clue what kind of kind of circuit i would need if a couple hundred or so LEDs surpass the power limits of the board.

I suggest making up your matrices of exactly 8 by 8 LEDs each and just buy three, four, five or whatever of these kits:

Or these ones

which used to be more expensive but are now actually cheaper and more useful if you wish to stack matrix arrays.

The point is that you do not install the matrix arrays from the kits themselves - or their socket pins, but just solder to the positions on the PCB and you have a durable and reliable assembly to drive your own matrix arrays.

Why did I say three, four or five? Well, you can fully assemble the first one as the matrix with which it comes and practice programming it. Then the others for your current project and maybe some for the next! :grinning:

taterking:
would the power consumption be a problem?

Not if you have a decent 5 V supply. Everything runs from 5 V, not some other. (These MAX7219 matrices draw 320 mA each.)

taterking:
would i need some sort of resistors in my curcut? where would I put them?

These modules include one current programming resistor. The MAX7219 does the rest. Don't even dream of driving them directly from your Arduino and the Mega is useless unless you have some really complex code and need its extra storage beyond a Nano.

Frankly, the only use I can think of for a Mega is with a larger graphic display that requires lots of pins and lots of code. :astonished:

4

LEDs can consume a lot of power. so, the best way is to use a driver of some sort.

It would seem that you could use the MAX7219.
but instead of driving an LED, drive an FET.

the FET would handle the power. the MAX7219 would handle the signal and your mega would just drive the chip.

I think people start with relays in a wooden box to deaden the sound, then move to SSR or make their own driver module.

for commercial LED's a full power supply with active current limiting is employed.

all the parts can be had, so you should not need to spend too much time soldering.
but the trade off is money to buy or time to make.

5

dave-in-nj:
It would seem that you could use the MAX7219.
but instead of driving an LED, drive an FET.

OK, I now want you to explain how you would do that?

6

Paul__B:
OK, I now want you to explain how you would do that?

The MAX7219 is basically a shift register that uses a serial input and addresses 64 outputs.
Crossroads offers a break-out board that has 64 individual LEDs.
CROSSROADS about 2/3 down the page

each output is controlled individually by the MAX7219

instead of lighting an LED, one could toggle an FET.

alternately, one could use a slew of shift registers or port expanders.

7

No, the MAX7219 is a multiplexer which addresses 16 outputs in two different ways. Each cathode driver - of which one at a time is selected - can drive 320 mA (absolute maximum 500 mA). If you were to tie the sources of eight FETs (logic level of course) to each of these with gates driven by the eight segment drives, then you would still be limited to perhaps 400 mA to drive the corresponding LED strings which could arguably be sourced by say, 24 V (seven LEDs in series) with the necessary current-limiting resistors as you have bypassed the current control mechanism in the MAX7219.

But who wants to wire up 64 FETs?

Just get some modules, wire 64 LEDs to each with no other components. :grinning:

8

Or use one my boards, which breaks out the MAX7219s 64 LEDs into wiring pairs that you can run off to wherever you want.
http://www.crossroadsfencing.com/BobuinoRev17

925×692 112 KB

9

Paul__B:
But who wants to wire up 64 FETs?

I think NO ONE !!! just because a thing can be done, does not mean is should be done.
I see people make 1980's vintage IBM PC's from simple chips.....

Just get some modules, wire 64 LEDs to each with no other components. :grinning:

YES !!!!! like stepper drivers, you 'can' use transistors, but a driver is complete, already designed, has more features than a home-brew version, so is better in every aspect.
unless soldering a few hundred connections is part of the goal.

10

say you have 24 bushes in the front of the yard. each will get 2 strands of lights, one green one red.
that would mean 48 signals if it is just off and on.

if you made a relay box, that would mean each strand would need to have an extension cord to that box.

If you made a module with a relay in the module so the strand was plugged in, then you would need 24 wires from your controller to the bushes. Assuming each module were to have 2 relays. it probably would make sense to have one box for every 2 bushes, or 4 strands.

then use simple CAT-5 network cable to send the signals.

if the strands are color changing, the problems are a bit different.
but the idea that the signals from the controller need to go to a device remains.

11

If you take 48 volts DC
and connect a certain number of LED's in series.
each LED will have a known voltge drop.

example : LED has a voltage drop of 1.5 volts. 32 LEDs would have a combined voltage drop of 48 volts.
So, by making a string of the correct number of LED's for the voltage on the power supply, you can treat them as ONE LED in the logic of the program. This one string would need one FET/Transistor/Relay to turn off and on.

generally speaking if you can turn on one LED, you can use that signal to your own needs.

if you had 10 strings of LEDs with wall plugs, you could control them with a relay, well, 10 relays, at line voltage.

I would hope that the OP would make a sketch of his area, window display, Christmas Tree, whole yard, house..... etc
show where each light would be, or each string of lights.

with more details, it would be easier to help guide you with details.

==============

as for the sequencing. that seems to be whole separate project.

12

Ok sorry for being a bit vague on the design in my original post. I was collecting ideas before dedicating to plans.

So after some research on what everyone suggested. I have ordered a neopixel strip like larryd suggested. seems very easy and strait forward. I also am using dave's suggestion of relay modules. this eliminates the need for a huge power supply. and I will be using standard AC powered strings.

I included the layout of my house in an attached drawing.

I will have all the windows, the front door, garage door and roof lights controlled on separate relays.
I plan to cut up my neopixel string to add some detail to the front porch.

so what i have made so far is a control box that contains all my boards and components. the box has 8 individually controlled AC outlets that is successfully changing to the music. the box is also a speaker box.

the weather should be nice tomorrow so we are heading out to hang the lights (while the kids paint and decorate the box LOL)

So my last question is....

can i cut up standard AC led string lights into whatever lengths I need without burning the house down? (assuming my box doesn't start fire first LOL)

house.jpg

13

house.jpg