PCB and potentiometer question

Discussion in 'Homework Help' started by droggie, Dec 24, 2012.

  1. droggie

    Thread Starter Member

    Oct 21, 2012
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    I have a question regarding the placement of the potentiometer pictured below. There are three solder points for each placement (RV1 and RV2), however I see an extra one in the middle. Is this one supposed to be a stand alone solder point or am I missing something?

    Also I am not sure if it is even a potentiometer. If it is, am I supposed to connect something external to it so I can physically control the current?
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The other middle point is for using vertical pots in stead of horizontal pots.

    Bertus
     
  3. droggie

    Thread Starter Member

    Oct 21, 2012
    137
    1
    So it's optional?
     
  4. tubeguy

    Well-Known Member

    Nov 3, 2012
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    Looking at the traces, you'll notice that 'extra' hole is connected to the hole where the pot fits. I'm thinking they made the pcb to accept either horizontal pots or vertical pots for options in parts procurement.

    Edit: I don't type fast enough
     
  5. droggie

    Thread Starter Member

    Oct 21, 2012
    137
    1
    I'm confused, because I did not get anything else with the kit for the pots; just the LEDs, resistors, caps, transistors and battery clips.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    In the vertical position, you can also use 10 turn potentiometers for easier adjustments.

    Bertus
     
  7. tubeguy

    Well-Known Member

    Nov 3, 2012
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    I recently got a Velleman Kit. It came with a parts list, schematic and parts stuffing diagram. That should tell you if you where supposed to get trim pots.

    You have a pot pictured...
     
  8. panic mode

    Senior Member

    Oct 10, 2011
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    it is common practice to give yourself some elbow room when shape of part can be changed.

    this forethought for example gives you option to use trimpot in either horizontal
    http://www.smcelectronics.com/TRIM25K.JPG

    or vertical position
    http://www.smcelectronics.com/TRIMPT22.JPG

    without making mess on the board.

    pads used for wiper are connected so it does not matter which shape you use. one of the pads would be unused.
     
  9. bertus

    Administrator

    Apr 5, 2008
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  10. droggie

    Thread Starter Member

    Oct 21, 2012
    137
    1
    I've posted a picture of the schematic. The thing is, I was not given a knob of any sort to adjust the speed. Do I have to purchase it separately or can I complete the circuit it without soldering the middle portion?
     
  11. panic mode

    Senior Member

    Oct 10, 2011
    1,318
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    RV1 and RV2 are used to slow down oscillations. if you don't have them you can remove them. astable multivibrator will still work with just R3 and R4 (but it may be a bit fast, aprox 7Hz or 7 flashes per second for each LED)
     
  12. Markd77

    Senior Member

    Sep 7, 2009
    2,803
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    I'm not sure you can get knobs for them, just use a screwdriver in the slot.
     
  13. tubeguy

    Well-Known Member

    Nov 3, 2012
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    Your other option is to get 220k or 250k pots with knobs and connect them with wires to the pcb.
     
  14. vk6zgo

    Active Member

    Jul 21, 2012
    677
    85
    Just solder the pots in where you have them sitting in the PCB in your original pictures.
    They are meant to be adjusted with a screwdriver,so you don't need any knobs.
     
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