Need help understanding schematic, I'm new!

Discussion in 'The Projects Forum' started by DBroadway, Apr 10, 2013.

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  1. DBroadway

    Thread Starter New Member

    Apr 10, 2013
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    Hey guys, I'm a volunteer firefighter, and I need some new strobes for my truck, so I figured, why not try to make them! Well, turns out that that's easier said than done. I found this schematic and a video that showed the system running. The video shows the wig-wag pattern that I prefer, so this looks perfect for me! The only problem is that I don't really know what I'm looking at. I don't know what these parts are, where to get them, how they work, or how to put them together. I have good soldering and other mechanical skills so I should be able to put it together if I can figure it out. So what I'm asking of you guys, is to help me understand what I'm looking at, and how to make it. Thanks for the help in advance!
     
  2. DickCappels

    Moderator

    Aug 21, 2008
    2,651
    632
    For starters, here are some potentially useful links. I suggest you start with the youtube video.

    http://www.youtube.com/watch?v=9cps7Q_IrX0

    http://www.instructables.com/id/HOW-TO-READ-CIRCUIT-DIAGRAMS/

    Things specific to your project, Q1 and Q2 are transistors, the electrode with the arrow is the emitter, the electrode that is a straight line that touches the vertical line is the base and the remaining line that touches the vertical line at 45° is the collector (abbreviated E,B, and C, respectively). The datasheet at the link below shows the physical location of the pins.
    www.solarbotics.net/library/datasheets/2N2222.pdf

    The IC1 and IC2 are quad Schmitt Trigger Nand Gates (four gates to a package) of the CD4093B type. Other part numbers that should work include the HEF4093B. Stay away from the parts that include numbers similar to "74HC" or 74HCT" in the part number because they are probably not rated to work at 12 volts. There are a lot others, each manufacturer having a different prefix, so the "4093" and "132" are the important parts of the part numbers. Make sure that the part you get has the same description, has a maximum rated voltage of at least 14 volts, and comes in a 14 pin package. The datasheet, at the link below, shows how to identify the pin numbers (there is usually a notch or a dimple at one end or corner) and to what pins to connect power.
    www.ti.com/lit/ds/symlink/cd4093bc.pdf

    The LEDs, the capacitors, and the resistors were explained in the video. Notice that the capacitors are polarized with the negative leads grounded. The capacitor voltage rating should be over 16 volts; use 25 volts for longer life.

    Start with small LEDs, the component values deliver about 20 milliamps to the LEDs. Start out small with low power components so that in case of an accident, you don't burn anything down (only half joking) or destroy any expensive parts. After you get this working with small LEDs at low power, there are plenty of people on this forum who can show you how to convert the circuit to drive much larger, higher powered LEDs.

    I suggest adding 100 uf/16 volts from the 12V power supply to ground.

    For your first project, you would probably be best off building it on one of those plastic plug-in breadboards, as shown in the video at the URL below, but when you do this "for real" solder it together on a circuit board and use sockets for IC1 and IC2
    https://www.youtube.com/watch?v=vJUX9cvyYjU

    The best place to buy these things depends a lot on where you live. If you are in the United States, Jameco is a good place to start, but some poking around on the web will reveal many distributors. Others can suggest outlets in other countries.

    That should get you started. Post here with any questions.
     
  3. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    The Terms of Service of the site don't allow for automotive modifications, as seen in Chapter 6.
    This is especially important for emergency vehicles.
    Imagine what could happen if your circuit by accident prevented the truck from starting in case of a need.

    You may find answers to your questions to one of the boards mentined in this thread:
    http://forum.allaboutcircuits.com/showthread.php?t=54400
     
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