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     DIY Electronics Kit 44: Switched PCB-Mounted 12v, 2.5a Relay
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  Edited 2016 (for personal use) by: James Davis, Beagle Buddy #227.
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Source: ftp://public.asimov.net/pub/apple_II/documentation/hardware/
        misc/Electonics - 12v 120v Switch.pdf
======================================================================


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INTRODUCTION
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This Kit has added a transistor switch to Kit 43.  A positive (+) 
signal of over +2.5 VDC (1/2 TTL-High) will turn the transistor on.  
To turn it off, the positive (+) signal should be brought back down to 
zero volts (TTL-Low).

Diode D1 provides a discharge path for the voltage [electromotive 
force (emf)] and/or (electric) current generated by the collapsing 
magnetic field of the relay coil when the power is removed.  Assembly 
is very easy and the only thing to make sure of is that you get the 
diode turned around (inserted in) the correct way.  The bar on the 
diode should match the bar on the PCB overlay.  [A really good direct 
current (DC) relay would already contain this diode internally!]

We have used a Goodsky RUDH-SH-112D 12V relay or equivalent.  Its coil 
resistance is 400 ohms and it is rated to switch (On/Off) 10 Amps at 
120 VAC [or 1200 volt-amps (watts)].


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COMPONENTS .................................................. QUANTITY
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Kit 44 PCB ......................................................... 1
3 pole terminal block [Positive-Signal, TTL-High and TTL-Low] ...... 2
3 pole terminal block [Common, Normally-Closed and Normally-Open] .. 1
Relay RUDH-SH-112D, or equivalent .................................. 1
1N4004 diode ....................................................... 1
5mm red LED ........................................................ 1
1K-ohm, ?-watt resistor [not included (in kit/list?)!] ............. 1


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SCHEMATIC DIAGRAM
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[See: Electonics - 12v 120v Switch.pdf]


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                                Page 1
======================================================================
     DIY Electronics Kit 44: Switched PCB-Mounted 12v, 2.5a Relay
----------------------------------------------------------------------
  Edited 2016 (for personal use) by: James Davis, Beagle Buddy #227.
======================================================================
Source: ftp://public.asimov.net/pub/apple_II/documentation/hardware/
        misc/Electonics - 12v 120v Switch.pdf
======================================================================


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COMMENTS
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1. I rephrased this advertisement's title & text quite a lot; because:

   a) The title of the PDF has the word "electronics" misspelled
      in it!--Unless the kit maker's company name is "Electonics."

   b) The original grammer was quite atrocious!

   b) The physics (electrical theory) described for the electrical 
      current discharge [diode (D1) and relay coil (RL1)] circuit
      was too general and not quite right.

2. The 1K-ohm, ?-watt resistor is not included in the original parts-
   list.  I have the following questions:

   a) What is its power rating?

   b) Is it included in the original kit or not?

3. The original parts-list had 2-pole and 3-pole terminal blocks.  
   The schematic diagram shows 2-pole and 5-pole terminal blocks.  
   I list two 3-pole terminal blocks, one for the direct-current TTL 
   voltage-level (+/- 5/12/24 VDC) circuitry, and one for the common
   alternating-current household voltage-level (120 VAC) circuitry.
   These terminal blocks (and all wiring) should be sized according to 
   international standards for the maximum currents and voltages they
   will be handling.

4. A really, really good direct current, TTL input-level, relay 
   would already contain all of this kits circuitry internally!
   Then, all this kit would need is the relay, and a matching relay
   socket; the two terminal blocks and the printed-circuit-board are
   replaced by the relay socket.  Somebody already makes these two
   devices.  You can find them for sale at your local electrical 
   supply or electronics store.




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