I need a design for an LED light sequencer? Need to light about 60 columns of LEDs, one column at a time.?

Question

Need to be able to vary the length of a cycle, and need evenly divided intervals between the columns of lights regardless of the length of the cycle. Need 40 LEDs per column.

Answer 1

There are cheap ways of doing this, but honestly I'd just use a PIC stamp or BASIC stamp for simplicity.

If that is impractical, you could use a sequence of thyristors with thermal switches...but that'd be annoying to build

Answer 2

Using a PIC is probably the way to go, since they're so simple to work with. However, they only have a handful of outputs, but you can use use a 1x64 decoder chip (or a combination of smaller decoders) to convert a 6-bit output into 64 channels.

To power the LEDs I would recommend using an n-type MOSFET at the low end of each column's power so you can control it directly with the decoder.

Also, when you're powering 40 LEDs in parallel, you should definitely use a resistor on each LED, otherwise you can get some really bad current sharing.

Answer 3

That's a lot of GPIO for a PIC. If you're lighting them in sequence, I'd get a CPLD with enough macrocells to give you the 60 outputs and a clock input. You can write a counter in the CPLD logic that will convert a the clock input to light up one of the 60 outputs. Use the CPLD outputs to enable the individual row drivers for the LEDs.

You can time it however you want by counting clock cycles...  

Answer 4

Logic circuitry and ucontrollers are not going to be able to drive the LEDs: not enough current or voltage capability. You will have to have drivers to handle the voltage/current. Also, simple shift registers can handle the logic without having to program a ucontroller or programmed logic.

I like minimalist designs, so I would start by dividing the LED's into 8 banks of 8 each, except 4 in last bank. This gives 60 LED sub-circuits, with a max of 64.

The banks are driven by a high (positive) side circuit, and a low (negative) side circuit.

The high side has 8 PNP (actually, I prefer P-type MOSFETs) transistors to drive the banks. So, first PNP transistor drives all 8 LED (sub-circuits) in the first bank, and other banks similarly driven, each by one transistor connected to all 8 (or 4 for the last bank) LED sub-circuits.

On the low (negative) side, use 8 NPN's (or N-type MOS) transistors to drive sub-circuit selector. The first sub-circuit in each bank is tied at the bottom to the first NPN, i.e. drives all 8 LED sub-circuits. Similarly, sub-circuits 2,3,4, etc. in each bank are connected to the corresponding NPN.

Basic circuit works by enabling single high side transistor and single low side transistor to select LED sub-circuit to actuate.

So, 8 bit shift registers are used to drive the high side drivers and the low side drivers. The low SR shifts a single enable bit (logic one) through, while the high side SR shifts a single enable bit (logic zero) through. This polarity is reversed because PNP have reverse logic from NPN.

A simple 555 timer circuit can be used to clock the low side SR; use a CMOS one for wider timing range. The ripple out from the low side SR drives the high side SR clock. Select 555 RC values to give desired pulse rate; this will automatically be uniform across all the columns. Use 10 turn pot to allow you to change timing by very small increments.

Set up reset on high side SR to reset after 60 rather than 64. You need to design resets and presets to properly start and reset circuits for both low and high side.

Set up the LED's in series-parallel for each sub-circuit, perhaps 4 x 10 or 5 x 8 for each column. Many folks like a resistor in series with each leg to limit current. I would try to go with 12, 15, or 24V to minimize current, but depends on ratings of transistors used and LED voltage/current requirements. Get the datasheet for your LED; I prefer to use accurate voltage supply rather than dropping resistors where LED characteristics allow it.

Use an adjustable voltage regulator supplying the high side drivers to adjust voltage across the LED's precisely.

Good luck!

Edit:

Chances are, this circuit is not available unless you can modify an LED clock circuit.

Perhaps you should google something like "digital clock" or LED clock. There are some that use LED's in a 60 column configuration. They are not going to have sufficient current, but otherwise would work. If you insist on proceeding, first step is to select your LED's, as the design progresses from the drive requirements. You need an LED with a datasheet, as to safely do the series/parallel thing, you need details of the LED performance.

You will need to consider how to package the circuit. For prototype circuit, proto-board is the most practical. Once the circuit is tested and finalized, if you want a permanent circuit, you can  make a custom PC board.  Expecting someone to design and test a complete circuit for free is not very realistic.

Without some interest and expertise in electronics, this will be a difficult project. Perhaps you can find a "ham" amateur radio group in your area that can help with building/testing the circuitry.