hey it's my first post here , ive been reading for a month or so and im gonna try and make my own plexi case sometime soon, i found a place that sells tons of leds (and resistors) cheap and i want to know if u guys have any ideas for what to do with them. I was thinking of making a spectrum analyzer like on bigger stereos and that stuff, but all i could find was schematics for a 3 bar one, I was thinking something like 16 x 12 or whatever size is convinient. Ideas and help accepted btw the store is: chi wing LEDs (ebay) thanks
I've bought from that guy on ebay, and it's good stuff. However, the high brightness of the leds makes them better suited for illumination than a spectrum analyzer. Unless you were to diffuse them by sanding the lense or even cutting it off they are painful to look at straight on. I used mine for case lighting, illuminating etches in plexi, and spotlights on my keyboard.
Or just run them at low current. Leds still glow on less than 1mA. Welcome, thecrownles LM3915 will do a 10-high column, for higher you can chain 2. Try a search, I'm sure we had some links a few weeks back.
I believe he's trying to make a 2D sterograph, one that reads inputs from various audio bands. Personally don't know how this is done, just know how to make it single-column meters, as cpemma said, with the LM3914.
ok ill try to make this clearer, i want to make it like the analyzers on radios where one end shows the 20hz intensity and the other end shows the 20khz intensity. From what i see it looks like the LM3915 does the actual intensity of the sound line (dB) . If you know how to wire this or have seen a guide that will be helpfull
You need a set of filters to split the sound into different frequency bands. There's a nice Rod Elliott Sound to Light circuit (figs 2-4) for 8 channels (x2 for stereo) that would feed 16 LM3915s to give a 16x10 display. Little snags are, design your own PCB, it needs a 12-0-12 split-rail DC supply, and 16 x LM3915 @ around $1.75 each. Not a cheap project to build...
ummm are you sure that that would make the bars vary with the intensity? from what the descriptions show it looks like they would just flash the row on and off. I'll look further into that but does anyone know where i might be able to just get a kit like the one in the anemone project? it doesn't have to be exactly the same... thanks for your help
ok ive looked at the circuit and i think it will work for me but what did you mean about i need to make my own pcb with a 12-0-12 power rail? could you show me to a guide or some explanation please. thanks
Rod Elliott sells pcbs for many of his designs, but not for that one, so it's not an easy n00b project. See the Useful Links for various guides. Mashie's Anemone one was a Velleman kit, now discontinued.
sorry, what i meant was what do u mean by a 12-0-12 split rail, and how can i get a -12 current if the molex connectors only have +12 +5 and ground?
You would need to make a power supply, since although you can pull -12V from your PC PSU, that's generally not a good idea. This is really easy to do with monolithic regulators (7812 and 7912) - have a look at the data sheets for example circuits. 12-0-12 split rail means a ground line (0V) with two power lines at +12V and -12V (as you seem to have worked out for yourself). I suspect you can get premade switching PSUs that will produce +/-12V from a single 5V line, or something - have a dig through other posts.
ok so i'm going to build the circuit, I think i can do that, but I searched everywhere and I can't find any way of getting -12 from 5 volts , the monolithic regulators that you mentioned only work if input voltage is higher than output, and there is no +14 rail from my psu, . I found a power supply that runs from the mains and has +/- 12 but I don't want to mess with the mains or have another (albeit somewhat small) power supply in my already tight case . If anyone knows where i can find this circuit or transformer? then please tell me, all your help is appreciated.
I have designed a circuit that works perfectly as a VU meter, but could be adapted to use as a spectrum analyser. I'm hoping to make one with 5 or so bands for my next case, so I'll be doing some more experiments in the fairly near future. Unfortunately I don't have a copy of the schematic online. I'll upload it tonight. Basically it uses 2 transistors per LED, and can run off anything from 5-15V DC. It has a wide-range response, but it's got an input filter that can be changed to suit the required response. If you have access to plenty of NPN transistors and have room for a medium-sized circuit board, it just might be suitable. IIRC it looks like this: Code: +5V --------------------------------- | | | | | [color=red] O[/color] LED | | | | > 3k3 | | < > 680R > 220k | < < | | | | | | | / | ---+----| BC549 33uF | / \ ------||---+[color=red]-----[/color]+----| BC549 | | | \ | 4.7uF = | | | | < 330k | | | > | | | | | | 0V -------------------------------------- edit: OK, that didn't work very well
lol ok try like getting a schematic program or something, I don't really need the schematics for the filter, what i really need is a -12 volt source that i can get in my computer. Maybe if your circuit is easier ill use that. After youve tested it of course .
I've got a schematic program, but the file is on my computer at home. I'd post it if I could access it from here... I built the circuit a couple of years ago. It still works Sorry, can't help you with a -V source I haven't worked with anything like that.
ok i guess ill just stick with the extra power supply idea, it has a -12 line and also can take the load of the 100 or so leds that are gonna be in my case off of the +5 line
EDIT: sorry, i just noobified myself, i was looking at it not paying attention. thats not a frequency filter, its a vu meter lol
Yep, that's right I forgot to mention, my circuit uses a fair amount of power. If anyone is looking at building this thing you'll need to use a ~500mA 12VDC power supply. It works OK with less, but the LEDs get progressively dimmer as more light up Here's a pic of the prototype in action. The right column is dimmer because I'm running a second set of LEDs in parallel
lamcdonald - just wanted to point out the error in your circuit - it says 200R = 2 * 100 R in parallel (not series!). I'm sure this was just a typo, but thought I'd best point it out!
