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What are you working on today/this week?

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Planning and ordering stage of trying to replicate an object from a tv show.

 

jgPr2.png

 

So I'm ordering some EL wire, and sampling some drivers. A inductorless driver, two resistors and two caps, plus a msp430 to add some fading/pulsing, all powered from a single cr2032.

 

Can't wait to see your prototype. Try squeeze in some real functions to it to make it more interesting. Ex. Couple of them sync / pulse when in close proximity, etc.

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Can't wait to see your prototype. Try squeeze in some real functions to it to make it more interesting. Ex. Couple of them sync / pulse when in close proximity, etc.

Maybe capsense on the caps so that it starts pulsing really fast when touched.

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@@cde, what tv show is it from?

 

Don't you want to make it standalone and independent of a terminal? 

 

Not really. I wanted to make something to play with to learn about how 6502s work. Remaking one of those trainers might be a neat project but it wouldn't be that useful. Like it is now I can add a 500x500 color screen or 1,000 LEDs or 100 buttons to play with. After I get the hang of assembly I will make something standalone.

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Can't wait to see your prototype. Try squeeze in some real functions to it to make it more interesting. Ex. Couple of them sync / pulse when in close proximity, etc.

Maybe capsense on the caps so that it starts pulsing really fast when touched.

 

Or maybe inductance sense with the LDC1000?

Get your friends together to pick up the pod, and it glows with 'mediocrity', while you pick it up (with a ring on your finger) and it goes berserk when you get close.

  :ph34r:

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@@cubeberg @@zeke

 

It's a sound locator thing that I am having trouble with.

I can catch which mic got signal 1st, but the time lapsed between them does not match what I expect.

I am trying to calculate by triangulation and get the fine direction of the sounding object. But I think I am getting not every clean signals from the front-end. I.e. every knock / clap generates ripples on both mics and I am not capturing the correct / definite pair.

I think I can only see them w/ a scope or logic analyzer. May be time to get / build one.

 

 

 

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@simpleavr: This is actually a hard problem. I played with it years ago for a directional  phase-array microphone, which is actually easier... direction is determined by calibrated delay in each channel.

 

Your mics look to have a separation of about 100mm. This is the wavelength corresponding to, roughly, 4Khz from the side aliasing to straight ahead, or about 40Khz from 6 degrees off center line.

 

(I was going to go into a long explanation/analysis, but I will keep it short: My current project calls and it will take a while to formulate a clear explanation)

 

Short form: you need the inputs matched very, very closely, both for phase shift and other delays (like ADC). 25microsec corresponds to on centerline looking like 6 degrees off, or 45 degrees off centerline looking like 35 or a bit more than 60 degrees (depending on orientation)

 

You need good high freq response to measure impulse timing, such as a book hitting the floor or a clap. Certainly better than 20KHz. The fast rise time is the key issue. The better the balance between channels, the lower the frequency cutoff can be, buy be careful of unequal phase shifts.  Probably can do it with a G-series. Might want to but a compressor in the front end and look for the gain change.

 

Best bet is cw detection and detect phase difference at the two mics at several frequencies. Why more than one? To reduce aliasing and increase resolution. Higher frequencies give better resolution as the phase shift can be more precisely determined at a given ADC resolution and sample rate. The lower frequencies give a good baseline timing (anything below 2Khz will be immune to aliasing at 100mm) for refinement if there will be aliasing at higher frequency. Not likely to be practical with a G-series MSP430, due to memory limitations (easiest to grab a sample and FFT), but probably doable.

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@@enl

 

Thanks for all the helpful pointers, I am certainly going to dig into them. I don't understand everything yet but I will educate myself w/ your pointers.

 

I am trying to build a turret shooting where I want to direct a turret towards whoever claps in a room. May be to point a video camera or throw candies at kids. So I am not trying to be really really accurate.

 

Still, it is currently way off (inconsistent, 1/4 times I can get reasonable readings). I am not doing ADC w/ the mic inputs. I am trying something simpler. I have the LM324 split for both channels. Each one has a op-amp 200x gain stage, plus a comparator to trigger a digital input for the G2553. I had one trimmer for both ends offset voltage (for comparator) and hope both sides are balance enough.

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I might suggest 4 mic's arranged in a square pattern, each pointing outward from each corner of the square. Three might be usable too.

 

mic       mic
    +---+
    |   |
    +---+
mic       mic
Then you could pick the two with the 'loudest' and 'closest timed' signals to home in on.

 

audio source
     |
    mic
   /
 mic

... and ...

audio source
     |
    mic
       \
        mic
... would seem to be equal with regards to propagation delays and such.

 

I'll shut up now.

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@@abecedarian

 

I had the same thinking. Trying to find a way or ways to filter out false alarms. Add redundancy and let them vote (say both set of mics agrees, etc) could be a solution. But I am finding that may be it's the quality of the front-end that's affecting the results. So I would 1st try to improve on them. The resistors are typical 1% types and there is nothing I can do on them. I may swap the electret mics to see if I can get a better match. It would be nice though to have a scope to see what actually happens. Now I am just doing trial and errors.

 

I tried to use interrupt tripping timer-on count to the other mic's interrupt (yes, trying to measure the difference between both "ears" hear the clap), and sometimes I did not get the other ear's interrupt.

 

Thanks for your suggestion.

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s@simpleavr: Actually, with a little code, you do have a scope, or an application suited substitute. The setup you have, with debugging interface, can be used to probe the behavoiur of the front end.

 

(Now, back to putting the new floor in my office. Only about 100sqft left on the finish floor. Oh, my aching back.)

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@@enl

 

I am doing what you had in mind. I had serial uart and I am capturing 100ms bursts of the digital I/Os from the 1st interrupt. Still, if problem is on the op-amp stage, a scope could help.

May be I should do FFT and get the mic via ADC, that way I will have more control (S/W filters, etc).

 

 

@@abecedarian

 

It's not the gain. It's more like matching both left and right to have the same gain and behave the same.

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I won't get to any serious development this week, but I'm at least thinking about how I want to approach it.

 

This is a LFM (linear fm) TDM (time division multiplex) MIMO (multiple input/output) S-band phased array radar that I built as part of an MIT summer course.  The current iteration is using an ATmega dev board to drive the transmitter, process the return and transmit it over USB to the host processing software.  The problem is that the MCU is somewhat under powered which is impacting the PRF.  The data transmission operation is blocking, so there is a fair amount of dead time that could be used for continuous pulsing.

 

So my goal is to replace the "brain" with something that has a little more horse power.  Right now I'm weighing my options between something with a Tiva series chip or a beagle bone black.  I'm also considering a DSP chip, but haven't looked very far into what my options are and how the DSP specific logic would benefit me since all the FFT's are done off board.

post-28692-0-03706800-1405439300_thumb.jpg

post-28692-0-98535400-1405439307_thumb.jpg

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I'm working on a reflow oven project. I wanted to keep all the mains voltage safely contained, so the triac/PSU part of it sits inside the oven casing. Whilst testing just this bit I set the oven on and just let it go, partly to see if the temperature inside the oven case (which can reach about 50C) would cause any trouble.

Anyway, this is what 280C does to a PCB that the thermocouple was attached to. It's only a little bit over reflow temperature, so I want expecting all the smoke and black gunk dripping out!

post-317-140544206352_thumb.jpg

The PCB was one of the daughter boards that came with RobG's nanopad. Sorry, Rob!

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