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Christmas Lights Simulator

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schristi69

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What I am trying to build is a simulator for programming what is called a Bellagio Pole. It is an 8 segament pole controlled by a Light-o-rama light controller and software. The segaments are made out of 100 cnt mini lights. The controller basically turns each segament on or off giving a VU meter like effect. I have purchased 32 Futurlec 5x7 led matrix displays to simulate each section. 1 matrix per section, 8 per pole for 4 poles. Every project I come across is for controlling each row/column on the matrix. What I want to do is just turn on the entire matrix when power is applied. I am new to electronics so have many questions. In the end I should have 32 modules that light when power is applied.

Power supplied will be 12v so I expect I will need something to lower this to the matrix.

How do I wire the matrix to turn on all leds when power is applied? Do I still need some kind of controller?

The matrix has 7 pins on top and 7 pins on the bottom. 1 for each row/column

Thought this would be easy, but now totally confused.

Attached are the only specs I have
 

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Diver300

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Most Helpful Member
The problem is that the 35 LEDs in each matrix are too many to have a wire for each one. That is why they are wired in rows and columns so that there are only 12 wires. They are designed to be lit one row or one column at at time, very quickly, and rely on persistence of vision to make it look as though all the lights are on.

LEDs are supposed to be lit with controlled currents. It's normal to put a resistor in series with an LED to control the current, and there are various LED calculators on the web to tell you what resistor you need. With the 5x7 matrix you can't separate out all 35 LED currents, so you can control all of the currents at the same time. That problem goes away if you light each column in turn, as you are only lighting 7 LEDS, with 7 connections, and each can have a controlled current while it is lit.

However, I suggest that you try resistors on both the columns and rows. For 12 V, and allowing about 15 mA per LED, you would get 75 mA for each of the rows and 105 mA for each of the columns. You've got about 2 V drop on the LEDs, leaving about 10 V. If you split that evenly, you have 5 V for the row resistors and also 5 V for the column resistors. Then you need 66.666 ohms (use 68 ohms as it is a standard value) producing 0.36 W (use a 1 W resistor) for each row. On the columns you want 47 ohms, also rated at 1 W.

That will ensure that each row and each column takes the same current, but there could still be variations between LEDs. I don't know how much that will be, so you'll have to try it. You must make sure that all the rows and columns are connected before turning on the power if you use this scheme, because the 75 mA or 105 mA is too much for one LED.
 

schristi69

New Member
So what you are saying is I must have some sort of controller chip to scan through and light each row (7) 5 leds at a time? My led units have 14 pins. So it looks like I will need several microcontrollers and led driver chips to drive the matricies. Then trigger the code to turn the lights on when the lighting controller sends a power signal. I can probably figure out the controller part. Have found many projects to run a single matrix. This is going to be harder than I thought. Better do some more reading. I added what specs I have for the matrix in the initial post.
 

Diver300

Well-Known Member
Most Helpful Member
I think that the modules have one wire for each row (5), and one for each column (7) plus a couple that are duplicated.

While it is best to control each LED current by scanning through the columns or rows, you might get away with 12 resistors as I described above.
 
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