Request for help on an LED bar graph circuit by an electronics noob.

[ThrowingChicken]

Apologies if this is not the right kind of forum for this, but it came up in my search and appears to be the kind if place I'm looking for.

I am a complete amateur when it comes to wiring and circuit boards; not even an amateur, a complete noob, I know next to nothing other than LED's require resistors to prevent them from burning out. What kind of resistors? I don't know. So please keep that in mind and bear with me.

That said, I am hoping someone here would be willing to help me come up with a simple diagram for an LED bar graph circuit made out of parts I can find at Radio Shack, online, or other small electronics stores that I can put together myself pretty easily (So long as I can solder and follow the diagram). The LED bar graph would simply bounce up and down, similar to what you would see on a stereos sound level graph, or what is seen in the video below, but the pattern does not actually have to represent a read out.

https://www.micsaund.com/wp-content/uploads/2006/02/bargraph.avi

The LED bar graph in the video was created to display the RPM of his hard drive, and from what I can tell requires special computer peripherals to program the circuit, which I'd rather not have to purchase.

There is another circuit I'm interested in too, preferably running from the same on/off switch and power source as the LED bar graph, but it doesn't have to, and it is much more simpler. It's just a couple of static LED's, a couple of blinking ones (no pattern), and a strobe LED that turns on at the press of a momentary push button.

Again, I apologize if I have come to the wrong place, and if what I am asking for is a bit more complicated than I think it is, please let me know. If anyone is curious what this is for, it's lights to go inside of a movie prop replica.

Any help is appreciated, thank you! And if you need any more info please let me know.

 

[ThrowingChicken]

Here is a circuit that preforms a similar function.
The controller causes the lights to light up one by one to full light, then the sequence starts over.
Maybe this schematic can be modified to work for my needs?

**broken link removed**

Since I made this thread I was thinking about the use of the bar graph LED, and I think it might be better
to use regular LEDs, or flat LEDS, as my space reserved for the LED Bargraph might be too irregular for it.
The display area is 1 3/8" x 1/4" which can comfortably house 7 large LEDs.

 

[Sceadwian]

I'd suggest picking up a 101 electronics projects kit and going through that until you get your footing. Starting off trying to make a circuit as depicted above when you know nothing is not a good idea.

Also, the micro controller programmer and chips the guy in that video used to make that LED bar graph will cost you less than all the components on the above circuit, and be easy and simpler to construct.

 

[ThrowingChicken]

Yeah but what are the computer peripherals going to cost me?

I can follow instructions pretty well, it's just a matter of having instructions to follow.

 

[Sceadwian]

You've obviously not googled for it then =) They use standard serial or parallel ports, if you want to build one yourself, printer port programmers are popular because they're 5 volt so they can interface directly with the micro controller with the right software (free)

 

[ThrowingChicken]

This might be way over my head. I don't even know what I'm Googling, heh.

Am I right in thinking a diode is like a check valve for current?

 

[Sceadwian]

Look it up on wikipedia as well (Wikipedia is an awesome general refrence) Micro Controllers. Specifically PIC's and AVR's (Microchip makes PIC's, Atmel makes AVR's) little IC's between 8 pin dip to 40 pin dip to 64pin TQFP and higher. Programmable computers in a single chip.

 

[ThrowingChicken]

Well something else I was thinking of, assuming diodes work the way I think they do, couldn't I get a cheep chaser kit and modify it for my needs?

From my understanding diodes are like check valves, meaning the current can flow in only one direction. So let me try to illustrate what I am thinking. Lets say that < or > represents a diode, and the direction the arrow points signifies the direction the current is alowed to flow. I'll use a dash (-) to represent an inactive LED, and a "o" to represent a lit LED.

If I have a chaser kit that "frame by frame" runs as depicted:

1. o------
2. -o-----
3. --o----
and so on till it loops back to 1.

If I set up diodes to send the current backwards will that create the stacking effect I am looking for?

1. o<-<-<-<-<-
2. o<o<-<-<-<-
3. o<o<o<-<-<-
and so on till the end.

 

[hvgap]

If your assuming that the electricity is flowing left to right then how would the electricity penetrate the first diode and even reach the second LED?

 

[ThrowingChicken]

Because the chaser kit lights each LED individually. Through the diode the active area in the normal chaser sequence, say light in the 4th place, is the one powering the LEDs before it. If the sequence lights from left to right, and the current flow allowed on the diodes is going from right to left, then the current would be sent backwards and lighting the previous lights... in theory.

 

[ThrowingChicken]

... 123456
OFF ------
F1. o-----
F2. -o----
F3. --o---
F4. ---o--
F5. ----o-
F6. -----o

But with the diode, current flowing from the right to the left, the lit area would allow current to flow back (<---) to the previous LEDs. Active LED 2 also powers LED 1, but when LED 1 is lit the diode prevents the current from flowing to LED2.
Active LED 3 also powers LEDs 1 & 2, but LED 2 does not allow power to reach LED 3... and so on.

F1. o-----
F2. oo---- (diode running current from LED 2 lights LED 1)
F3. ooo--- (diodes running current from LED 3 light LEDs 2-1)
F4. oooo-- (diodes running current from LED 4 light LEDs 3-1)
F5. ooooo- (diodes running current from LED 5 light LEDs 4-1)
F6. oooooo (diodes running current from LED 6 light LEDs 5-1)

 

[kchriste]

The LED bar graph would simply bounce up and down, similar to what you would see on a stereos sound level graph,

Look for a project that uses the LM3914/15 like this one:
http://www.electronics-tutorials.com/devices/lm3914.htm
And feed it with a peak rectified signal from an audio source like a radio / sound card so you get that random bouncing effect just like a VU meter because it IS a VU meter.

It's just a couple of static LED's, a couple of blinking ones (no pattern), and a strobe LED that turns on at the press of a momentary push button.

For blinking LEDs, Google for "LED flasher" and you'll get hits like these:
**broken link removed**

 

[ThrowingChicken]

Thanks! I'm getting some interesting results so far, even some VU meter kits for just a few bucks.

I'd still like to know if my theory on the diode modification of a chaser sequence will get the effect I think it will, if someone can pipe in about that

 

[hvgap]

haha, im sorry, i did not read the chaser kit part. For whatever reason i just thought that you were talking about a circuit where all the LEDs were lit and then the diodes were going to somehow make the graph go to full. Sorry about my misunderstanding.

 

[ThrowingChicken]

But would it work on a chaser kit?

 

[ThrowingChicken]

Looking at the chaser kits a lot of them look like they all share a common current, most of them show a positive current going straight to each one of the lights, so then shouldn't I be able to put a diode letting the negative current flow backwards? Will that work? If so, what kind of diode would I need?

 

[Sceadwian]

LED's are already diodes. I think you need to pick up a basic electronics book at a library before you go trying projects like this, you don't have even a basic understanding of how the devices work.

 

[audioguru]

Looking at the chaser kits a lot of them look like they all share a common current, most of them show a positive current going straight to each one of the lights, so then shouldn't I be able to put a diode letting the negative current flow backwards? Will that work? If so, what kind of diode would I need?

You can make a chaser circuit into a Knight Rider where the LEDs light back and forth. Outputs 1 to 5 light 5 LEDs one after the other. Then a diode from the 6th output lights the 5th LED again, a diode from the 7th output lights the 4th LED again, a diode from the 8th output lights the 3nd LED again, a diode from the 9th output lights the 2nd LED again and a diode from the 10th output lights the 1st LED again.

 

[ThrowingChicken]

LED's are already diodes. I think you need to pick up a basic electronics book at a library before you go trying projects like this, you don't have even a basic understanding of how the devices work.

I know what an LED is, and I had a vague understanding of what a diode was; like I kept asking, is it like a check valve?

From Wiki:

In electronics, a diode is a component that restricts the direction of movement of charge carriers. Essentially, it allows an electric current to flow in one direction, but blocks it in the opposite direction. Thus, the diode can be thought of as an electronic version of a check valve.

I can also follow directions, so I have no problems putting together a chaser kit, it's the modification for my needs I don't know much about, but if all I need to do is add several current restricting diodes to the circuit then won't I be on my way? If I'm wrong then just tell me I'm wrong. Saying I need to dig into some books to understand what I am doing is a given, I know that, but a simple "no, it won't work" would be a lot more helpful.

 

[ThrowingChicken]

You can make a chaser circuit into a Knight Rider where the LEDs light back and forth. Outputs 1 to 5 light 5 LEDs one after the other. Then a diode from the 6th output lights the 5th LED again, a diode from the 7th output lights the 4th LED again, a diode from the 8th output lights the 3nd LED again, a diode from the 9th output lights the 2nd LED again and a diode from the 10th output lights the 1st LED again.

So if you can do that with a chaser kit and diodes then I should be able to get the effect I'm after, right? Seems like it could be a yes and no type answer. It sounds like I can sent power back to the previous LEDs, but it seems like that power might not be enough to fully light all the LEDs on the circuit.