Suggestions for Audible Identification of Numbers on Three Digit 7-Segment Display?

Discussion in 'General Electronics Chat' started by MrZener, Apr 4, 2014.

  1. MrZener

    Thread Starter New Member

    Apr 4, 2014
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    Hi all.

    I'm new to this forum, and it looks like it's a great resource for electronics enthusiasts. Before jumping to my question, I thought I'd first share a brief description of my project. I'm going to be building a little, battery powered handheld device in a project box to help synchronize audio and video when recording video on a DSLR and recording audio on a separate audio recorder. The device, also commonly referred to as a "bloop slate", is fairly simple and usually consists of a lamp and some variety of audio buzzer. The device is activated while the camera and sound are rolling, so the camera captures video of the LED turning on, the audio recorder captures the sound of the buzzer, and voila...you have a synchronization point for editing.

    To help identify individual takes and for this simple system to work, a take number usually has to be written on the bloop slate in dry erase marker to identify the take visually, and someone has to call out the take number to identify the take number on the audio track. That said, I'd like to take this concept a few steps further and come up with a system where visual and audible indication are both handled electronically.

    I've decided how I'm going to handle visual identification of the take number. I'm going to use three 7 segment displays, each driven by a CD4033 decade counter and pushbutton clock input, to facilitate the display of numbers 000 - 999. That's the easy part. The more difficult part is working out some sort of audible indication to correspond with the number being displayed, and that's where I'd like some advice and suggestions.

    A couple of thoughts have crossed my mind...perhaps using 3 piezo buzzers of different frequencies, each corresponding to one of the 3 digits, and having each buzzer momentarily beep "x" number of times, depending on the value of its associated digit. Of course, to make this work and identifiable on the audio track, the buzzers would need to work in series, and so the electronic logistics and practicality of that are a little iffy. Another option that I like a little better would be somehow having the device play a quick 3-digit DTMF sequence of the digits on the three 7 segment displays, but then I don't know how easily DTMF tones can be generated. Regardless of which audible alert I choose, I'd also somehow like to use the CD4033 outputs to drive the audio circuitry (so that I don't have to manually enter the 3-digit number elsewhere for the audio circuitry).

    So, is this doable? If so, is there something I could come up with using the CD4033 and other discrete components for the audio portion of the device, or is this starting to border on the type of project that would be better handled by some variety of microcontroller? Any suggestions or ideas, specifically regarding the audible identification of the displayed 3-digit number, would really be appreciated. Maybe I'm over-thinking the audible side of this project, and there are some ideas that are much simpler than what I've considered.

    Thanks!
     
  2. elec_mech

    Senior Member

    Nov 12, 2008
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    193
    Welcome to AAC.

    I can't say I follow how this is used, but is this what you want to happen?

    1. Set value of take, either with a simple clock signal or somehow entering in a three-digit number
    2. Press button and three-digit value is displayed on three 7-segment displays and a unique audio signal is played/generated

    I won't claim this is the simplest method, but what comes to mind is using a microcontroller to play a wave or MP3 player or use a text-to-speech module.

    With an MP3 module, you could record your own voice and make ten files: 0-9, then depending on the three-digit value (also controlled or interfaced to the microcontroller), you play three files. So for take 397, the microcontroller would play "three", "nine", "seven". If you want to go nuts, you could make 1000 recordings then play the specific one you need: "Take three hundred ninety-seven".

    If a robotic voice is okay, you could use a text-to-speech module, also controlled with a microcontroller. So instead of messing with MP3 files, you simply send a command.

    If you are only interested in unique tones, you could program the microcontroller to have a piezo buzzer emit a specific tone or sequence (perhaps morse code?). You might swing DTMF codes with a microcontroller, but I'd have to research this. I don't follow how you'll interpret the tones, DTMF or otherwise, if you go this route though.

    For kicks, you could then control this with a simple IR or RF remote so you don't have to leave the camera to change numbers and play the audio.

    While I don't see this as a super complex project, it would not be for the faint of heart either. Do you have any experience with microcontrollers? If so, which chips and languages are you familiar with?
     
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    For tight sync you want a visual flash that is exactly one frame in duration, and an audio chirp, usually gated 1 KHz, that is timed to the flash. For super tight sync, the two signals are triggered by a sync signal from the camera, but that probably is a bit beyond this project. The imortant part is that the leading ege of the flash is sync'd to the startof the chirp. Without camera sync, your ambiguity will be +/_ 1 frame.

    All of what you speculate is doable. The discrete approach has less overhead and will git r dun, but modifying it as you think of new features will be difficult. A uC can do most of the heavy lifting if you already are familiar with one and have a development system, usually just some downlodable software and a small usb device programmer.

    Touch tones are easy to generate with a specialized single chip, or that too can be foldd ino the uC. A shift register could be used to trigger the three tone pairs in sequence.

    ak
     
  4. MrZener

    Thread Starter New Member

    Apr 4, 2014
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    Thanks for the replies and suggestions. I did some microprocessor programming back in college, but that was over 10 years ago, so if I was to consider going the microprocessor route, I'd essentially have to start from scratch in terms of learning a new development system.

    AnalogKid mentioned something about generating DTMF with a specialized chip. Does anyone know off-hand what chip(s) are capable of generating DTMF?

    Thanks!
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    DTMF is the wong choice in my opinion. Decoders can require 40-50mS of tone before they give an output.

    I would just use a 555 etc to make a high pitch tone, like 2.5 kHz.
     
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    As I read it, there are two separate functions for the tone. One is to sync the audio track, for which just about anything will work. The other is the audible indication of the displayed number. In this case the decode delay is not important (as long as it is within 1-2 seconds). In fact, if it is part of your normal activity to listen to touch tones, you quickly learn to "hear" the numbers. So a corresponding decoder would be more of a training tool than a long-term requirement. IMH-been-there-done-that-O

    ak
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Thinking about touchtones in a post-DIP world. Scanning a bunch of circuits, here's a list of some chips to hunt for. Some of the numbers are missing prefixes and/or suffixes.

    Yahoo: touch tone circuit <no quotation marks>

    TPS380
    ME8900
    MC14410
    5089

    And when all else fails, it's Hans Camenzind's masterpiece to the rescue. Attached is a TT generator based on two 555's. The circuit is similar to the original TT pad.

    ak
     
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Or you can use a mcirocontroller (PIC etc).

    I did one here;
    http://www.romanblack.com/SG/SG_tutorial.htm#DTMF

    That generates proper dual-sine DTMF, with accurate sine waveshapes and very accurate frequencies. Complete with "twist" to counter high frequency loss from recording or transmission;

    [​IMG]

    Hardware is a PIC, and a resistor and a capacitor. :)
     
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