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61  Using Arduino / LEDs and Multiplexing / Re: My RGB LED Stairs Illumination video on: October 24, 2011, 04:43:28 pm
Oh that makes sense.

So do you upload a new program each time or do you have like 1 microcontroller with 1 program and then another with a different one and then a main switch with on-off-1-2-3?
or how do you change from light show to light show?

Also did you need a carpet foot to get under the carpet?

I upload a new program each time.  Except when I want to demonstrate it, the program will be the basic light up and light down routines.  I am going to code in a double tap on the pressure sensor to put it in demo mode so I don't have to upload a new program each time.  Holidays will require uploading a new program to use special lighting patterns as well.  But again, if I want to make it totally computer free, I could use a double tap to go into a mode selection menu that will alternate between patterns with tapping of a pressure pad.

Right now, since I'm changing the program fairly frequently, I have a laptop plugged into the board in the closet under the stairs and I log into the laptop from my upstairs office (Remote Desktop) to do the programming. 

I have not placed the top pressure plate under the carpet yet.  Downstairs, it is wood flooring and there was already a runner at the base of the stairs so the plate went below the runner.  Upstairs, it is on the carpet and I threw a mat over it.  Once I am confident enough that this solution will work long term, I will put the upstairs pressure plate under the carpet.  I don't know what the 'carpet foot' you mentioned is though.
62  Using Arduino / LEDs and Multiplexing / Re: My RGB LED Stairs Illumination video on: October 24, 2011, 03:48:16 pm
So i'm also curious, what kind of pressure sensor did you use?  Like, say i stepped on the left side and then the sensor was in the center.  How does the sensor cover the entire step?
100# flexforce pressure sensor.

To ensure that it is activated, I sandwiched the sensor between two 1/16" stainless steel plates.  The pressure sensor has a dab of hot glue on each side of it and the plates have dabs of hot glue between each corner.  This ensures that even if you step on the outer edge of the plate, it will still transfer pressure to the sensor.

In the breadboard setup, I also experimented with:
  • IR LED emitter and IR detector - this was the most complex solution to set up since the emitter has to blink at 38kHz, be aligned with the detector, and require much more power.  It would also be hard to eliminate dog triggering without mounting it high and then it would be hard to make it blend in.
  • IR proximity detector - this brought it down to one package to install but it requires a lot of depth to mount making it hard to blend in.  The range is only about 36" on it but on a staircase, the width is only 30" so technically would work well.
  • PIR sensor - this also would require a lot of depth to mount (~2") although not as much as the IR emitter/detector above.  Blending in issue is still there using this.
  • Ultrasonic sensor - this could be rigged up two ways for versatility.  Either one at the top and bottom shooting across to the other wall or two in the middle of the facing staircase 180° from each other.  The advantage of the middle is that I could do an installation of one box housing both of them and could track people on the staircase as well as where they were on the staircase.  Theoretically, I could have lit the stair they were on a different color.

I decided on the pressure sensor for simplicity.  It was easy to set up and easy to blend in.  If after a period of time I discover these don't work as well as I would like, I still have the hardware to implement one of the options mentioned above.
63  Using Arduino / LEDs and Multiplexing / Re: My RGB LED Stairs Illumination video on: October 24, 2011, 02:55:36 pm
Well i mean a series circuit is, for example, having leds one after another on one line of power.  Where as a paralell would be more having 1 led part off into its own line and then reconnect.

Are you using any capacitors on your project?

Gotcha.....the control circuit is series but the LEDs would be parallel.  Each is individually powered and sunk to its own pin on the TLC5940.  Yes, I am using capacitors.  A 100nf and 10uf capacitor worked fine in breadboard but then when I powered the breadboard from my wall wart and 5v regulator, it had issues so replaced a couple 100nf with 1000nf and no more issues.  It would have likely worked with just the 100nf once everything was on PCB because another noise issue on the breadboard causing intermittent flickering went away as well.

The VR I'm using is rated at 1.5A so I am pretty much peaking it out.  When I used a 12V power source, it got over 300°F and went into thermal shutdown which is why I started using the 7.5V power source.  If I run all the lights at maximum brightness (RGB on each LED) for an extended period of time, it will still get pretty hot but won't go into thermal shutdown.  But since I'm not ever running at full power but for brief transitions, and most of the time it is well below 1A, it only gets slightly warm.  I'm still putting small fan in the box it will reside in just to be on the safe side though.
64  Using Arduino / LEDs and Multiplexing / Re: My RGB LED Stairs Illumination video on: October 24, 2011, 01:45:40 pm
I'm assuming that the led pins are all in a paralell circuit, right?
Otherwise what are you using to power the whole thing?

Not sure as to exactly what is meant by having all led pins in a parallel circuit but the circuit design uses 6 TLC5940s that are in series.  The data out for the first drives the data in for the next and that data out drives the data in for the next and so on...

The first two TLC5940s drive the red, the second two drive the green and the last two drive the blue.

I used this library for the control of the TLC5940s:

Peak amperage that I saw was about 1.4A at 5V and I am using a 7.5V, 2.5A wall wart as a power supply.
65  Using Arduino / LEDs and Multiplexing / Re: My RGB LED Stairs Illumination video on: October 24, 2011, 10:52:44 am
are you addressing each RGB Led pin separately?

Yes.  The 3 boards below the processor board are addressing each of the colors and each has 30 pins for each LED (2 on each step).  I could have used multiplexing to reduce the number of TLC5940s, but the wiring would have been the same so I decided to ensure maximum brightness by driving each separately.

The processor board also provides the +5V pin headers for each of the LEDs.
66  Using Arduino / LEDs and Multiplexing / Re: My RGB LED Stairs Illumination video on: October 24, 2011, 10:37:15 am
A few details on the project.....(
(click on the images for a larger version)

This is the opening I cut below the staircase to route the wires.....still need to patch it.  I used 28ga and 30ga ribbon cable for the wiring...I cannot see any difference in brightness levels between them. 

This shows the stacked boards with ATMega328 board on top.  Basic setup with pin headers to allow reprogramming without removing the IC.  Yes, that is a rubber band holding several heat sinks on the voltage regulator.  That will be removed once it is in a box with a small fan.  Currently, it barely gets warm with normal use but when I'm running it constantly for testing or demonstration, it does get a bit warm.

Side view of the boards that shows the pin headers and 6 TLC5940 LED driver ICs.

Bottom view of boards

Messy looking but will look better once it is mounted in a box...
67  Using Arduino / LEDs and Multiplexing / Re: My RGB LED Stairs Illumination video on: October 24, 2011, 09:55:53 am
Why is there blue in the Christmas theme?
I thought christmas was all about the red and green

Those are the main colors you see in non-lit items for x-mas.  But for lights, it's all about multi-colors. smiley
68  Using Arduino / LEDs and Multiplexing / Re: My RGB LED Stairs Illumination video on: October 23, 2011, 10:37:11 pm
Finished up the stairs this weekend.  Pressure senors installed and calibrated.  LEDs mounted.  Light sensor installed and calibrated.  All that is left is to tidy up the mess in the closet under the stairs. 

$2/year to operate this cool night light. smiley

69  Using Arduino / LEDs and Multiplexing / Re: Texas Instruments TLC5940 explanation on: October 21, 2011, 04:30:08 pm
Thanks for the help on this Gumpy_Mike! smiley


If I use 8 legs to achieve 350mA for a single color and the voltage drop is 3.8V

PD= (5 * 0.03) + (3.8 * .044 * 8 ) = 1.49W

So if I want to design for full power and have some headroom, I need to use 3 - 5940s (one for each color) and multiplex them across the 4 LEDs. 
70  Using Arduino / LEDs and Multiplexing / Re: Texas Instruments TLC5940 explanation on: October 21, 2011, 03:43:11 pm
I have 4 - 3w RGB LEDs
You won't drive those with a TLC5940 it's power dissipation is limited. Also the maximum current for any one channel is 120mA and while you can parallel up channels for the 28 pin DIL package the total dissipation is just 2.058W. Note however that is package dissipation, which depends on the voltage you feed to the anodes. See page 13 of the data sheet for how to calculate the package dissipation for any situation.

Good point....forgot about considering the package power dissipation limit.  I've looked at the formula but to be honest, all the variables confuse me.  

VCC: device supply voltage
ICC: device supply current
VOUT: TLC5940 OUTn voltage when driving LED current
IMAX: LED current adjusted by R(IREF) Resistor
DCn: maximum dot correction value for OUTn
N: number of OUTn driving LED at the same time
dPWM: duty cycle defined by BLANK pin or GS PWM value

LED Specs are:
Forward Voltage   2.2~2.8V(Red), 3.0~3.8V(Green), 3.0~3.8V(Blue)
Forward Current   350mA
I will be using a 5V 8A source from a power supply like this:

Could you help me out here?    I will not be using dot correction but will be using PWM to control brightness levels for color shifts on the artwork.  I don't mind using multiple 5940s as I have 10 on hand for projects.  
71  Using Arduino / LEDs and Multiplexing / Re: Texas Instruments TLC5940 explanation on: October 21, 2011, 01:53:59 pm
Not quite.
Yes you can connect one RGB LED to three diffrent outputs of the chip. That is what I do in the mini monomer project I poster earlier.
Don't mix up what a schematic tells you a circuit must be and how to physical realise it.

That makes my next project much easier.  I have 4 - 3w RGB LEDs that I am going to use to replace the halogen tracklight bulbs that are illuminating some metal artwork.  I can use just one 5940 to power this rather than 3.  3 legs for each color and multiplex the 5940 across the 4 LEDs.  Now I just have to figure out how to power it in very limited space.  smiley
72  Using Arduino / LEDs and Multiplexing / Re: Texas Instruments TLC5940 explanation on: October 21, 2011, 08:36:50 am
I have a general question about the TLC5940 that I'm curious about....

Since it is a current limiting chip, can you hook up all 3 cathodes of an RGB led to it?  Can it independently adjust each channel to limit current?  The single project I've completed with these used separate chips for each color.
73  Using Arduino / LEDs and Multiplexing / Re: simple 8x8 matrix on: October 20, 2011, 10:42:10 pm
I used 6 TLC5940's for my stairs project.  I have grown fond of these controllers.  They offer so much capability for the price.  I've bought 20 of them off eBay for a very good price.,76094.0.html

I could have used 3 and multiplexed but I wanted to ensure the every LED had the most current available to it.  smiley

They are working great!

I started the project trying to use AS1107's but couldn't get it stable with RGB LEDs.  They source and sink current and have digital and analog brightness control.  I will be using them on a LED matrix in the near future.

If you are willing to wait a bit, look to eBay for your LED needs as well.  I've bought common anode diffused, common cathode diffused and common anode non-diffused RGB LEDs from there as well as 1000 blue LEDs.  As a matter of fact, I've spent about $1000 over the past two months on eBay buying stuff mostly from overseas.  LOL.  I'm new to this hobby and have gone overboard like I do with my other hobbies.
74  Using Arduino / LEDs and Multiplexing / Re: My RGB LED Stairs Illumination video on: October 20, 2011, 10:29:30 pm
Thanks. smiley

Just finished getting the light sensor and pressure sensors installed and calibrated.  Dog won't set it off but a person will.  And it won't come on during the day.
75  Using Arduino / LEDs and Multiplexing / My RGB LED Stairs Illumination video on: October 20, 2011, 01:10:21 am
Updated video at several posts down....

This is not quite completed but shows it almost done.  I'm in process of testing animations and timing.  Items to complete are:
  • add the pressure sensors
  • mount the RGB LEDs in blocks
  • put the PCBs in a box
  • patch the big hole I cut in the closet

I am illuminating the stairs using 30 RGB leds.  Control of the LEDs is done using an ATmega328 processor (Arduino) and 6 TLC5940 LED driver ICs.  Pressure sensors will be used to detect someone going on the staircase which also allows me to calibrate it so my dog won't trigger it.  A light detector will be used to only trigger it at night.

I am adding themes to the animations so at the end of the video, you will see the Xmas theme.  A halloween theme will be added that will have red pulsating lights.  Other holidays, I haven't quite thought of yet.  

This is the first project on the Arduino I started on a couple of months ago and while waiting for parts, I built some LED cubes. It took a long time to plan, breadboard a prototype and then install.   There are 120 wires that had to be run under the staircase to the closet underneath.  This project is not for the faint of heart!  LOL.

Peak amperage is about 1.4A @ 5V being regulated down from a 7.5V 2.5A wall wart power supply.

Here is a photo of the breadboard design:

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