Alot of HELP with LED Project Welcomed!!! :)

[Asgard1]

OK, First off let me say that my E-skill at best is minimum! I have searched high and low for information to help me with this project and I am on information overload I think! I have read every thread in the forum relating to "LED" as keyword and have found a few points that might help, but right now, I think I have bit off more then my share taking on this one but here it goes...

These are the LED's I am working with:

7- orange- VF 1.7v @ 20mA
8- UV- VF 3.6v @ 20mA
1- Red- VF 1.7v @ 20mA

As for power I was figuring on a 5v PS (but flexible... what ever is best!)

I would like to build a circuit that when a tactile button is pushed it would have the Red LED light up immediately and stay on. Then in 2 seconds intervals have each of the 7 orange LEDs light up and stay on (LED1, 2secs, LED2, 2secs, LED3, etc). Then after all the orange LEDs are on have the 8 UV LEDs turn on and stay on for about 5 seconds and then have all the LEDs shutoff, until the button is pushed again to repeat the process.

Note* As for Electronic terminology... lol... I have a dictionary around here somewhere! I just need to be pushed...or shoved in the right direction on this one. In my defense I have completed many projects when given even semi-decent instructions. Any help here will be welcomed... GREATLY!! Thx in advance!

 

[logbook]

You won’t find much anywhere related to "LEDs" to help you because frankly that is not the problem. Let’s suppose you decide to use the 5V power supply. Turning on the LED consists of connecting it across the power rail through a resistor to define the current.

Let’s take the orange LEDs.
VF is 1.7V. Ok so that means 5 - 1.7 across the resistor, provided the switching device doesn’t ‘lose’ (drop) too much voltage. You want 20mA so that means a (5 - 1.7)/(20E-3) = 165 ohm resistor. You might pick 150R, 160R, 180R depending on what is conveniently available.

If you can’t repeat this process for the other colours then give up

That was the easy bit. Now comes the circuitry to switch the LEDs. As you are a computer guy you might like to program the function into a PIC micro-controller. Of course if you don’t have access to a PIC programming interface, compiler etc, this option is impractical.

In that case you need to get a bit more ‘technical’. There are probably many ways to implement this complex function. Here is my first thought. The switch starts a ramp generator. This consists of an opamp wired as an integrator. You will find this configuration in application notes and so forth. The ramp ramps up slowly. I would suggest ±12V or ±15V power rails for this approach.

Suppose the ramp goes at a rate of 0.5V/second. You set level comparators at 1V intervals and when a threshold is crossed a new LED comes on. We are now talking about resistive dividers from the power rail to set the threshold levels and say quad comparators in 16 pin packages. The ramp will do all the timing; all you have to do is set thresholds and act accordingly.

This is not a complicated problem for an EE, but for a non-EE could be challenging. You have to be able to use transistors on the comparator outputs because one comparator will not drive 8x UV LEDS (=160mA). You could use a power MOSFET for this function, controlled by the comparator.

If you look at comparator data sheets you should see how to apply them.

You can also get thermometer bar code display chips which will do some of the work for you.

 

[peebee]

Another thought for the control circuit -- use a 1-second clock and a digital counter to drive the LED's. Probably not the cheapest way to implement this thing, but it'd be easy.