Need help with this circuit diagram

Discussion in 'The Projects Forum' started by liltimmy, Mar 11, 2009.

  1. liltimmy

    Thread Starter New Member

    Mar 11, 2009
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    0
    Hi, im fairly new to the whole electronics thing but I have a couple of questions.

    This is to do with two electronic bass pedals:

    "This schematic shows the circuit needed. Note that it requires its own 5V power supply - one based on the simple LM7805 should be sufficient and can be powered from a 9V battery.

    You should be at least somewhat familiar with electronics to assemble this. If you don't know what a 5V power supply is or why you would need one, you're going to have trouble if you try to make one of these.


    "Make sure you get the 74HC14 Schmitt-Trigger Hex Inverter. The 7404 will not work. All of the diodes can be pretty much any kind. The 5V relay should be normally-open and should be non-latching. The transistor is a 2N3904, but any garden-variety NPN BJT should do.

    What happens is that the closing of either input switch (i.e. either pedal) causes the output (the relay) to close for a short time, then re-open - regardless of whether the input pedal is still down or not.

    This allows pedal #1 to be pushed down to trigger a Bass Drum hit, then while pedal #1 is still down, pedal #2 can be hit to trigger another Bass Drum hit! When working both pedals at once one after theother, this allows for some very fast bass drumming."

    [​IMG]


    That's the circuit diagram and here are my questions:

    1. What should I use where it says "jack"? I know I need two female jacks. The pulses are sent via a regular 3.5mm mono jack but im not sure how I would connect the jack to the leads leading into the breadboard.

    2. What is a 5v relay? and where would i buy 1 (bearing in mind it has to be non-latching and normally-open)?

    3. Similar to question 1, how would I wire the male audio jack that would be connected to the outpu
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    I wrote some comments in the drawing.

    [​IMG]

    1) you will need the "counter" part that fits the 3.5 mm jack.The female jack will have a couple of solder contacts, these can be connected to the input.

    2) A relays is a switching device. It contains a coil (that rates 5 or 6 Volts), the coil will interact with a couple of contacts wich can open and close if there is current or not.
    More information on relays can be found in the links of this page : http://www.educypedia.be/electronics/relay.htm

    3) Inside the male jack there are solder contacts, you can mount wires on the contacts that go to the realys contacts.

    Greetings,
    Bertus
     
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Usually, for stage music, the jacks and plugs are 1/4" so a more durable cable can be used.

    You would need 3 jacks (of whichever diameter), "Mono", only one ring. There are two parts, "Tip" (pointy part) and "Ring" (the sleeve/shaft).

    Wire the Tip of the jack to the resistor heading towards ground, and the ring or "sleeve" to the +5V. This is the same way telephone operator plugboards were wired, with the tip grounded, so if the operator missed the hole, there wouldn't be a spark. Also, if mounting in a metal case, the case can then be grounded as well.

    For the relay output, It appears to only connect the tip to the ring of the plug, so one contact of the relay would go to the ring, the other to the tip. Polarity is unknown from diagram.

    The plugs, jacks, and 5V SPST Relay can all be found at Radio Shack. You will need to find out what the maximum current flowing through the relay to decide what the contact rating should be.
     
  4. liltimmy

    Thread Starter New Member

    Mar 11, 2009
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    0
    thanks for the help! I purchased a relay from maplins seeing as I live in the UK and therefore radioshack is inconvienent.

    http://www.maplin.co.uk/Module.aspx?ModuleNo=37494
    1A DPDT 5Vdc N05AW £1.9

    I'm confused by the markings on the underside of the 5v relay.

    2 pins are clearly related to the coil.

    the lower 6 look like this:

    [​IMG]
     
    Last edited: Mar 13, 2009
  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
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    The left side is one pole, the right side is the second pole. The top and bottom are the two "Throws" of the relay.

    When the coil is not energized, the Normally Closed (NC), top two contacts of each pole are connected.

    When the coil is energized, the Normally Open (NO), bottom two contacts of each pole are conneted.

    The middle connector on each side is common to both NO and NC, if you only need a connection when the relay is on, hook the power between the left middle and left lower, or right middle and right lower. Two channels could be switched at the same time using the left and right sides on two outputs.
     
  6. liltimmy

    Thread Starter New Member

    Mar 11, 2009
    4
    0
    thanks for the info!

    Another question:

    This is the top 2 pins (above the other 6)

    -------------diode (black end)-----
    | |
    | PIN -----(coil diagram) ---- PIN |

    The is how the part of the chip is positioned at the moment.

    Do i power the relay from the right pin of the coil?

    -------------diode (black end)-----
    | |
    | PIN -----(coil diagram) ---- PIN | ---------- +5v

    By doing that?

    Thanks for your support and I look forward to reading your reply!
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    The Diode should be across the coil, and point against intended current flow when used for inductive kickback protection for a transistor, usually Cathode/stripe towards positive.

    Generally, relay coils do not care which direction current flows through them to engage, unless they have a built in protection diode, which yours does. The positive should go to the negative/cathode side of the coil.

    I can't quite make out what is being described in your post, I hope the description above makes sense.
     
  8. liltimmy

    Thread Starter New Member

    Mar 11, 2009
    4
    0
    Therefore is this the correct configuration? :

    [​IMG]
     
    Last edited: Mar 14, 2009
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