DIY hearing assisting magnetic neck loop help

Discussion in 'The Projects Forum' started by geratheg, Jan 1, 2016.

  1. geratheg

    Thread Starter Member

    Jul 11, 2014
    107
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    I need help understanding some components in the schematic in the following link: http://archive.siliconchip.com.au/cms/A_112366/article.html I know it might be outdated, suggestions for newer devices welcome. I'm going the DIY route just out of curiously and it being cost effective.

    I'm confused about two components:
    1. I don't understand what component ZD1 is assuming it's some kind of diode. I'm hoping to find some exact diodes to use for ZD1 or some suggestions would help.
    2. In the picture of the assembled schematic, some capacitors look like ceramic disk capacitors but others look like rectangular boxes. What kind of capacitors are those? Does it matter which kind I use? Also curious about why if you know.

    Thanks!
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
    970
    1- ZD1 is a 4.7V zener diode
    2-All capacitors are drawn the same... some are just polarized though (hence the +/- included with those)
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,986
    745
    Zd1 is a zener diode as stated, its used as a low battery monitor in this circuit, the led will go out when the battery is below 6.5V approx.

    A zener diode conducts as a normal diode in forward mode, but in reverse mode is open circuit until it's voltage is reached, then it will conduct.

    The capacitors with -/+ are Electrolytic caps, and have to be polarity connected correctly.
     
  4. geratheg

    Thread Starter Member

    Jul 11, 2014
    107
    3
    I've never used a zener diode before (I'm still a student). Does it matter which type and code numbered I use as long as it's rated at 4.7V? Or is there only one type?

    I attached pictures that show the capacitors. There are two that are yellow in color, one that's greenish, and one that's grey. What types of capacitors are those? Would it matter if I used another type?

    Thanks.
     
  5. sailorjoe

    Member

    Jun 4, 2013
    361
    63
    The green square thingy is a variable resistor, value of 10k, with a logarithmic scale.
    The two gray square thingys are small capacitors. If you can pull the part number off the case you can look it up to see what type it is.
    The yellow square thingys are just resistors.
    Parts manufacturers modify their packaging to accommodate the needs of automatic machines that stuff parts into circuit boards. So identical types of parts can look very different.
     
  6. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,986
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    Zeners come in a range of voltages and wattage, just use the voltage that the circuit needs, any wattage will do smallest is approx 400mW, no need for big wattage as the circuit doesn't use a lot of power,

    The capacitors are polyester and Electrolytic types, resistors are the blueish blocks with coloured stripes.
     
  7. geratheg

    Thread Starter Member

    Jul 11, 2014
    107
    3
    According to the layout image, the yellow boxes are capacitors. I'll go ahead and just try polyester types for that, unless other suggestions are given.
    Thanks for all the help.
     
  8. geratheg

    Thread Starter Member

    Jul 11, 2014
    107
    3
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