designing and building a nixie tube audio spectrum analyzer  - Page 1
Forum section: electronics / projects

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: April 10, 2013, 09:48:05 pm
content: hello everybodyone of my latest projects that i am currently designing is a nixie tube audio spectrum analyser. i do have a few questions on it to ensure i do it correctlyso the first step is to amplify the incoming signal but i do not know how much byi am currently deciding whether to have it single channel or dual channel but i am currently leaning towards dual channel. so yea what would i need to amplify the input to initialy?secondly the amplified signal then goes into multiple band pass filters which look like this i believe :i have a few quetions on this: 1, is this the best band pass filter or is there a more reliable version? 2, where does my output go on this version is it between C1 and R1? and my third question is what are the most common frequency bands used in a spectrum analyser?once the band pass as done its thing i need to convert the signal that comes from it into a pwm signal or some signal to control an npn transistor to control the nixie tube (bar graph tube) i do belive that this is the best way to control the nixies due to there high voltage.speaking of voltage what would i need to step mains voltage (230V 50Hz) down to the required voltage of 140V DC (according to the datasheet) i know it will need a transformer to drop 230V AC to aproximatly 140V and then a bridge rectifier to convert it into DC voltage, i then need smoothing capacitors but i am unsure of what values to use on this and where to put them.if you would like a schematic of what i have so far then just let me knowthe whole spectrum analyser will have several tubes attached to it so the power supply needs to come off of mains ( i do have a DC-DC 9-12V-140V converter but this only does 21mA so it is not powerful enough to run all of the tubes at once (it is hover enough to power my nixie tube clockwhich runs off of a 9V battery or 12V DC supply.any help on this would be brilliant and thanks

author: Skimask
author_rank: Super Contributor
timestamp: April 10, 2013, 10:51:43 pm
content: If it was me, I'd pull the input audio signals thru a couple of opamps, into a couple of ADC inputs of a PIC, run the analog input samples thru some FFT code, and fire that data back out X number of channels of PWM, out to some higher voltage interface, then out to the tubes...But you're not shooting for that...so...instead of all those bandpass filters, might I suggest this:https://www.sparkfun.com/products/10468Easy enough to interface with an MCU (if you're into that sort of thing) to get a bunch of relative band strength outputs.The real question I've got, is why nixie tubes? Don't most (if not all?) display digits? Or are you going for a brighter/dimmer digit effect?

author: kizzap
author_rank: Unknown
timestamp: April 11, 2013, 03:12:42 pm
content: Ironically I am working on a similar project of my own, however I am not going the nixie way-just using a load of LEDs.Couple of notes:Amplifying the input signal is not an issue that you just pick a random value for. You have to understand what sort of stuff is going to happen to the signal further down the signal chain. To top that off, you need to know what the input of the circuit is going to be. For my design, I am working around using the computer speaker output, and the best information that I can find on that is that the output voltage will get to a 1V peak.Secondly, I would recommend using an op-amp based bandpass filter.http://sim.okawa-denshi.jp/en/OPtazyuBakeisan.htmis a good help for creating the filters.I'm not sure about how driving the Nixie tubes would work so I can't help you there, but I did just findhttp://tchips.com/nixie-music-visualizer/<- this website which might be of a whole lot of assistance.finallyhttp://sound.westhost.com/project136.htmis another good website to have a read through of, It might spark some ideas.

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: April 13, 2013, 09:25:41 pm
content: thanks, i shall ahve a look at them in the morningive got some bar graph nixie tubeshttp://tubehobby.com/show_det.php?det=1these are the kind i have which display a bar of color in varing length depending on the current going into it