Electronics Really Cool Idea...Have the entire circuit designed...

Really Cool Idea

Well I have this awesome mod for this project I am doing. The project is here, and it is called Homestarrunner.com computer, if you have not seen it yet:

Homestarrunner.com Computer

I have not talked about this idea on the log yet and I kind of want it to be a surprise, so keep this on the down low….

Ok well enough with the other crap, here is my idea.

I have made an entirely new faceplate that is made of steel. I have a stealthed CD in it and a hole for the floppy drive and a hole for the eject button on the floppy drive. No LED’s, no buttons….just blank. Personally I think it looks really cool. I might paint it or sand it a bunch but sure yet.

My idea is that I will make window in the front that uses a piece of frosted (sand with fine sandpaper) plexi glass. I will have another piece of plexi behind this one that will have LED’s in this design:



That is about to scale too.

It may look a little confusing right now but let me explain. I will first have the “H”, lit by red LED’s, light up for a short time (more than 1 second, less than 5 seconds), and then go out and have the Star light up, lit by red for the same amount of time, go out, and then I will have the “R” light up, lit also by red LED’s, and then go out and repeat the cycle.

I am pretty sure that I should use 555 timers but I am not positive. I have some electrical sense but I am definitely no expert. I can solder and such too. But I need help figuring out the circuit.

My other big concern is that how can I run 21 yellow 3,000mcd, 2.4V LED’s at one time, and then get them to light up all at the same time.

While we are discussing the properties of the LED’s, the red ones are 7,000mcd, 2.4V. I will only need to light up 12 at one time and 14 at one time.

If needed I can post pictures of the faceplate so far and the frosted plexi I am working on but this thread really isn’t that concerned with that.

Thank you!!!!!!

 

I think I see how this circuit would work. This might take a little breadboarding to get it just right though.

A 555 would provide the clock. There's nothing time critical here (who's going to notice the difference between 1Hz and .8Hz?), so a 555 is OK. The 555 feeds into a 4017 decade counter. The 4017's outputs feed into an NPN transistor to drive the appropriate set of LEDs (2n2222A ought to be enough, max output of 500mA, 21 ultrabright LEDs is 420mA; enough, but it'd probably be a good idea to heatsink the transistor).

Lemme bangup a schematic and post it, then I'll talk about what you might need to tweak, as it's more helpful if you can see what I'm talking about.

 

If you can post the current rating it would be good, i am guessing by 2.4 you mean 2.4voltage drop? (copy + paste specification saves you time )

 

Ok, here's what I banged up in about 5 min.



Sorry about the mess, things got a bit crowded, and I wasn't going to spend too much time cleaning up. Basically, 555 is set up in astable mode, didn't give any component values on purpose, because they're not important right now. Now, the 4017 is setup to give you the effect you want with a clock that's faster. Look at Q0 + 1. The diode off of Q1 sends the output to the transistor, while the diode at Q0 make sure the signal from Q1 doesn't go back into Q0 while it's low, causing a short and making you swear (most likely). If I were to feed a 2Hz clock (.5s) to the counter, than the transistor feeding off of Q0+1 would be on for a full second (.5s * 2). If you can get a stable clock in the 1Hz to .2Hz area like you want, then simply eliminate the diodes, and hang the transistors off of Q0, 1 and 2, then tie reset to Q3 (or Q4 if you want an off period).

Whoops, just read that you do want an off period between each stage. Unfortunately, if you find that the 555 clock doesn't work below 1Hz, you can do the diode idea, then the best you can get is H, off, star, off, R, then back to H. Q0+1 will be the H series of LEDs, Q2+3 will be open, Q4+5 will be the star series of LEDs, Q6+7 will be open, Q8+9 will be the R series of LEDs. If you find that the 555 does work that low, then Q0 is H, Q1 open, Q2 star, Q3 open, Q4 R, Q5 open, Q6 tied to reset.

Oh, and one last thing. If you can, you should actually run the LEDs in series-parallel. For the star, run 3 LEDs in series with a (12-7.2)/.02)=~240 ohm resistor, 7 of those paralleled, running of of +12v supply. For the R LEDs, same as above, only 2 strings paralleled. For the H series, 4 in series, with a (12-9.6)/.02=~120ohm resistor, 3 of those paralleled.

I hope that's enough info.

 

I think the idea of using a 555 coupled with a logic counter is probably the way to go, but if you wanted it is possible to do with several 555 timers (one for each stage). This ultimately has greater component count and is probably harder to make, but a little easier to understand. I will try a find a schematic if you want (I remember I made an LED traffic-light simulator years ago using a 555 for each stage).
PS. I would be tempted to use larger drive transistors (T0220 case style) just to be sure, I fear 22 LEDs is too close to the drive limit of the 2222, and its easier to get effective TO220 style heatsinks. For the sake of a few pennies, its probably better not to take the risk!

 

whypick1: Ok first off THANK YOU VERY MUCH FOR THE DIAGRAM!!!!!!!!
Second is that i don't mind having an off period bewteen each set of LED's i just don't want to have an off period between each LED.

Munterofamodder: If you could find that ciriut that uses multiple 555 timers that would be great becuase i am willing to try several different methods.

Thank you again!!!!!

 

Not if you run on 12v & put 3 or 4 in series...

 

surely the power disspated by the transistor due to the load will approach, if not exceed, the 500mW limit. I make it nearer 1.5W of power.
oh, regards 555 circuit, I can't find it at mo. It was either from a Babani book of circuits by the venerable R.A.Penfold or from a thin Radioshack book of 555 circuits. It was so long ago I cant really remember, but if I recall it was complicated to wire (on stripboard). To be honest, I think doing it as mentioned above using a logic counter\divider would be the most practical.

 

What kind of IC is IC 1 in that diagram of yours whypick1?

 

CD4017 like I said earlier. The description is "10-stage divider/counter with decoded outputs" (decoded parts means that there's 1 output per stage, instead of something like binary). If you're thinking about RadioShack, you can forget about it since they have ****. Here are three good places to get them online.

 

Thanks for the links, I just placed an order for some of the 4017 IC's and some 555 timers from Jameco so i should be able to start on this project pretty soon!!!!!!!!!!!!

Thanks again for all the help!!!!

 

lol your obsessed
id like to see it when its done

 

Perhaps a little too late to be useful, but have you considered using several layers of plexi and just etching where you want the 'lights' to be? This approach would also allow you to have continuous lines instead of dots.

Essentially, you etch a pattern into a piece of plexi then light the whole thing up from the side. The etched pattern catches the light, causing it to glow (sortof). Metku has a nice article on doing this with a CNC router here - I have seen people doing this by hand too. You can get multiple shapes by layering several sheets of plexi and multiple colours by using several different colour LEDs.

 

I just read over that and i think i may try it and see how it works. That may look better than the other design but i don't know. THe main thing i am worried about with using the first method, the one with individual LED's, is that i don't know if people will be able to reconginze the letters or the star.

 

why not use the same LED's for parts of the R and H (ie. the solid line at LHS and top and middle)?

 

I had designed a LED layout this way before i designed the one that is posted but The R wasn't centered in the window so it looked kind of weird.

But thanks for the idea!!!

 

Ok i have been looking at this circuit some more, while waiting for my stuff to get here, and I have a couple of questions about it.

First, what is the IC1P part about?

Second, on the very left of the diagram there is a resitor, and then a wire that only one end is connected, what is happening there?

Third, in the upper right near the U$1 there is an arrow, what is that going to?

Don't lose any sleep over these questions just i keep realizing that i know even less than i think.

Thank You!!

 

1. Power connections for the 4017
2. That's a potentiometer. Third leg is disconnected because I didn't know whether or not the circuit would work with that leg grounded (which is good practice).
3. +5v. I took off a few layers to make the schem easier to read, it would've said +5v if I hadn't. That's the typical symbol for the positive supply.

 

Ok one FINAL question on the circuit.

Do i need to connect the same volteage amount to the 555 timer as the 4017 IC?

I would think not because the timer is only acting as a timer and not powering the LED's but this may be totaly wrong.

I thank you again for all your help!!!!

 

Not essential, but you'll need to connect the two ground (0v) lines from each supply. Why do you ask? Usually easier to fit both chips on the same board with same supply...