Need help from you electrical engineer types

[XMEN Iceman]

I need a circuit design to make 16 LED's, arranged in a 4 x 4 grid, flash randomly. I want to put them in front of a computer case in order to make it look like an old mainframe computer with the lights flashing on the front.<br><br>Can any of you throw together a design for a 12 volt circuit for me? I will solder it together on a board.<br><br>Thanks,<br>David <p></p><i></i>

[XMEN Durango]

radio shack has led lights that flash or stay on. to different bulbs. all you do is wire them to a board.<br> <!--EZCODE IMAGE START--><img src="http://www.thzclan.com/hosted/durango/photo.1.jpg" style="border:0;"/><!--EZCODE IMAGE END--> <p></p><i></i>

[XMEN Ashaman DTM]

Sure can.<br><br>Do you have a place where you can get electronics?<br><br>You'll need the LED's, resistors, capacitors (ceramic and electrolytic), a bunch of transistors. You'll also need a clock generator, more transistors, or another chip that can do several voltages (I'll have to double check the part number for the last one).<br><br>But the circuit is easy. <!--EZCODE EMOTICON START :D --><img src=http://www.ezboard.com/images/emoticons/happy.gif ALT=":D"><!--EZCODE EMOTICON END--> <br> <p></p><i></i>

[XMEN Gambit]

Asha, we have Fry's, of course, and Ft. Worth is HQ to Radio Shack, and down by me there is the HQ of Mouser Electronics, a huge national supplier of components like that.<br><br>So, yes, we can get our hands on parts. <!--EZCODE EMOTICON START :) --><img src=http://www.ezboard.com/images/emoticons/smile.gif ALT=":)"><!--EZCODE EMOTICON END--> <p><!--EZCODE IMAGE START--><img src="http://www.xmenclan.org/xmengambit.gif"/><!--EZCODE IMAGE END--><br>XMEN member<br>Card-carrying DTM<br>OKL Fish-napper<br><br>Though a program be but three lines long, someday it will have to be maintained.<br><!--EZCODE ITALIC START--><em> The Tao of Programming</em><!--EZCODE ITALIC END--></p><i></i>

[XMEN Ashaman DTM]

Okay. Next question:<br><br>Ice, you going for a compact design that may be a bit more difficult to set up?<br><br>Or do you want something that's a bit less compact, but also a bit easier to set up?<br><br><br><br>And what are your power specs? (Voltage and current)<br>If you are coming straight out of a power supply, you are either at 12 or 5 Volts, and can have a LOT of current. Well, a lot from my point of view which is embedded systems (typically 5 V and 300 mA).<br><br>Also, are you able to buy a little PCB kit? One that's got the holes, but nothing is connected? Don't buy one where you have to do the masking and etching yourself (the chemicals are hard to use and dangerous without proper equipment).<br><br><br>Also, you want several LED's on different timings so that the lights switch on and off in an apparently random manner? Or do you want a progression or counting scheme? Say a binary encoder? (Which looks really cool when hooked up to a pulse generator.) <p></p><i></i>

[Ambush Bug]

Icey wants <!--EZCODE ITALIC START--><em>blinkenlights</em><!--EZCODE ITALIC END-->! <p></p><i></i>

[XMEN Gambit]

<!--EZCODE ITALIC START--><em>Ja, der blinkenlighten!</em><!--EZCODE ITALIC END--><br><br>Hehe. Yes, we can get those boards, Asha. <p><!--EZCODE IMAGE START--><img src="http://www.xmenclan.org/xmengambit.gif"/><!--EZCODE IMAGE END--><br>XMEN member<br>Card-carrying DTM<br>OKL Fish-napper<br><br>Though a program be but three lines long, someday it will have to be maintained.<br><!--EZCODE ITALIC START--><em> The Tao of Programming</em><!--EZCODE ITALIC END--></p><i></i>

[XMEN Ashaman DTM]

Still need to know the power specs. <!--EZCODE EMOTICON START ;) --><img src=http://www.ezboard.com/images/emoticons/wink.gif ALT=";)"><!--EZCODE EMOTICON END--> <br><br> <p></p><i></i>

[Spinning Hat]

It's an ATX Power supply, so wouldn't that be pretty standard? <p><!--EZCODE HR START--><hr /><!--EZCODE HR END--><!--EZCODE CENTER START--><div style="text-align:center"><br><!--EZCODE FONT START--><span style="color:red;font-family:Arial;font-size:medium;"><!--EZCODE ITALIC START--><em>"Never, Never, Never Quit"</em><!--EZCODE ITALIC END--> -Winston Churchill</span><!--EZCODE FONT END--></div><!--EZCODE CENTER END--></p><i></i>

[XMEN Ashaman DTM]

Yep. Just making sure that I didn't get the wrong components. <!--EZCODE EMOTICON START ;) --><img src=http://www.ezboard.com/images/emoticons/wink.gif ALT=";)"><!--EZCODE EMOTICON END--> <br> <p></p><i></i>

[XMEN Ashaman DTM]

Okay Ice. Here is a schematic:<br><br><!--EZCODE LINK START--><a href="http://home.myuw.net/mcraw/images/circuit/random.bmp" target="top">three LED circuit</a><!--EZCODE LINK END--><br><br>This circuit is set up for three LED's. You just pick your color of LED, and attach one side to the A, B, or C output, and the other to the common ground. If you put it in backwards, it won't light up. So just switch it to the proper polarity. Most power supplies won't put out enough current to hurt something like this. (A bad one might.)<br><br>If you need to add more LED's, just use this circuit as a guide:<br><br><!--EZCODE LINK START--><a href="http://home.myuw.net/mcraw/images/circu ... om_add.bmp" target="top">three additional LED's</a><!--EZCODE LINK END--><br><br>You just connect the Vcc line to the other circuit's Vcc line, and make sure the grounds are all common. If you only want one, then choose the farthest right circuit. The two on the left in the second figure have a feedthrough so that the input of one is the input of the other. (IE: they share the same input.)<br><br><br>Now... the capacitors (all the symbols with a C next to them, and the ones that don't have a C next to them), will all have to be 10 micro-farads. Just chose that so that it's easier to order the parts, and for some reasonable timings.<br><br>The resistors are a bit different. You can choose any resistors you want between 10 kilo-Ohms and 100 kilo-Ohms. Anything below that, and you have too quick of a circuit... above that and things get too slow. All the resistors are marked with the symbol next to the letter "R". For "Rb", I'd recommend a pot... one that doesn't go above 50kOhms or below 10kOhms. (Again, timings and safety.)<br><br><br><br><br>A parts list follows:<br><br>555 timers. Preferably the DIP kind... they're easier to work with IMO. You'll need one more than the number of LED's that you intend to use. So if you have 7 LED's... you'll need 8 555 timers. Also, make sure they are rated for +5 to +15 volts.<br><br>Capicitors (ceramic kind... NOT the electrolytic kind). These usually come in bags of 10, 20, 30, 50, or 100. You'll need 4 per LED that you'll use. A bag of 50 should be plenty... and you'll have spares if one blows.<br><br>Resistors. These also usually come in bags. Get a variety between the ranges that I specified. Don't sweat tolerances... just be sure they are within 10% tolerance.<br><br>A pot. One of the kinds with three leads. Should have a range between 10 kohms and 50 kohms. Always use the center lead and one of the outside ones. Putting this into the "Rb" place will allow you to adjust how fast the pulse generator circuit operates.<br><br>A breadboard. These are the most expensive pieces of hardware. For a three LED circuit, you'll need one that is about 8 inches long. I'd avoid a PCB. They can be a hassle to wire properly while avoiding shorts. Also, get one of the breadboards that you can just plug stuff into. That'll be easiest.<br><br>A switch. This can be a toggle switch, or a DPDT switch of any kind. It doesn't matter. You just need a switch that can perform the "on/off" function. Try to get one that looks good though.<br><br>Female 4-pin molex connector.<br><br><br>Once you get everything, plug it all together how you want it on the breadboard. Do NOT apply power until you have double checked that things are wired according to the diagram. Only then should you apply power.<br><br><br>Now... from what I can gather on the molex connectors that come with ATX power supplies, the wires go like this:<br><br>Red: +5 V<br>Black: (both wires) ground<br>Yellow: +12 V<br><br><br>I'd advise against using the Yellow wire at all for this circuit.<br>To hook it up: attach one black wire to your ground line in the circuit. Then attach the red wire to your switch, and the other end of the switch to the Vcc line in the circuit.<br>Plug the molex connectors together. then switch on your fancy switch you just bought. THEN turn on your computer.<br><br><br><br>I assume that you can mount the LED's, switch and pot some place. And I'm also assuming that you can mount the breadboard in a good place. Just be sure that the components can NOT be shorted and you should be fine.<br><br><br><br>If you don't want the switch in there, just hook the red wire of the molex connector directly to the Vcc line. That way, when you turn on the computer power, the lights will come on. <p></p><i></i>

[XMEN Ashaman DTM]

DOH!<br><br>Just reread your original statement. You can use the 12 Volt line on the molex connector. But try to use the 5 V one first. Unless you can specifically ask the mouser guys for LED's that are rated for 12 V. The other components should be fine at that voltage. <!--EZCODE EMOTICON START :D --><img src=http://www.ezboard.com/images/emoticons/happy.gif ALT=":D"><!--EZCODE EMOTICON END--> <br><br> <p></p><i></i>