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Breadboard and my microcontroller.

Discussion in 'Microcontrollers' started by danielsmusic, Dec 10, 2008.

  1. Gayan Soyza

    Gayan Soyza Active Member

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    Off Topic!

    When I design sign boards I first choose correct high efficiency LED's or LED Matrixes.So I can drive them with a low duty cycles later to minimize the power consumption without notifying any brightness changing situations.
     
  2. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Yes, this is why we asked for the COMPLETE circuit, and it shows a complete lack of required capacitors - you need a capacitor on the input pin of the 7805 as well, and a good size electrolytic across the battery.
     
  3. danielsmusic

    danielsmusic New Member

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    I did initially have a capacitor either side of the regulator. I noticed that it seems to slow down the clock speed on the PIC so I removed them.

    EDIT: Only tried >1uF cap on output, I will try the recommended 0.1uf when I get home. And some across the battery.
     
    Last edited: Dec 11, 2008
  4. dave

    Dave New Member

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  5. petrv

    petrv New Member

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    you should never leave out the capacitors. I always put 0.1uF ceramic to both input and output of 78XX and also electrolytic capacitors (both on input and output). Also it is highly recommended to put 0.1uF ceramic capacitors to each digital IC (as close to its power pins as possible). Otherwise you can experience some "unexplainable" problems especially at higher speeds and with logic ICs that are fast (high slew rate) and switching bigger currents ....
     
  6. danielsmusic

    danielsmusic New Member

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    Adding any sort of capacitor anywhere in the circuit completely stops the PIC and it does nothing.
     
  7. petrv

    petrv New Member

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    If adding a capacitor between +5V and 0V (power supply) stops it from working then I guess your circuit must have much more serious problem than it seems.
     
  8. danielsmusic

    danielsmusic New Member

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    With a very large capacitor across the battery terminals it will stay flashing a bit longer than without any capacitors at all. Although having the same capacitor across 5v and 0v it won't work at all.
     
  9. 3v0

    3v0 Coop Build Coordinator Forum Supporter

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    What voltage is the battery?
    What voltage does the volt meter show for the battery?

    You really should post the schematic for this thing starting with the battery. It could save a lot of time and posts.

    A picture that was good enough to follow the wiring would be good too.
     
    Last edited: Dec 11, 2008
  10. danielsmusic

    danielsmusic New Member

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    12V

    13V

    I posted a picture a bit further up.


    EDIT: Here's something interesting, if I hold an output pin on the PIC high with a small load (LED), it works with a 0.1uF capacitor across the battery, but as I add more across the IC etc it will slow down the PIC although the pattern is still there.
     
    Last edited: Dec 11, 2008
  11. blueroomelectronics

    blueroomelectronics Well-Known Member

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    Take a photo of your device, with the caps. Why are you using a shift register why not just drive the LEDs directly from the PIC?
    PS the 74HC595 can only source a couple of mA (it can sink more than it can source) Your LEDs need about 470ohms if you wish to drive them from the 74HC595.
     
  12. AtomSoft

    AtomSoft Well-Known Member

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    what if you change the power source(battery) try using another source. Also check for floating pins. I think i used to get similar issues when a pin is left floating and i didnt disable the interrupts.
     
  13. danielsmusic

    danielsmusic New Member

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    I'm hoping that when this is sorted out, I will be driving a lot of LEDs.
     

    Attached Files:

  14. AtomSoft

    AtomSoft Well-Known Member

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    what kind of wires are those? Exposed?
     
  15. danielsmusic

    danielsmusic New Member

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    The smaller ones are, yes.
    No luck with floating pins, I set all the I/O pins to output.
     
    Last edited: Dec 11, 2008
  16. kchriste

    kchriste New Member Forum Supporter

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    As per your breadboard picture:
    Make a little room by moving the PIC downwards one set of holes. Then put the crystal and caps right next to the OSC pins of the PIC. Don't use long wires like that for the crystal as it will cause these types of problems.
    Get some insulated buss wire, cut it to various lengths and strip 1/4" off the ends. Use that instead of bare buss wire which is prone to shorting out.
    You should also get rid of all those "croc clips". Those are notorious for intermittent contacts.
     
    Last edited: Dec 11, 2008
  17. theo92

    theo92 New Member

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    Why these non coated wires on the breadboard?
    A small touch can create a lot of problems.
    I think it all should be small hook-up.
    They're very cheap, looks cute, breadboard socjet easily accept it and easy to use.
     
    Last edited: Dec 12, 2008
  18. danielsmusic

    danielsmusic New Member

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    I'll try some enamel copper wire when I get home and move the crystal directly to the PIC. I'll post the results a bit later on.
     
  19. mike50

    mike50 New Member

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    The 7805 regulator you are using appears to be in a TO-220 case. That device, with no heatsink (as in your breadboard) has a maximum power dissipation of about 2 watts. With 12 volts input it must drop 7 volts across the regulator. You are drawing at least 250 ma. This requires the 7805 to dissipate 1.75 watts. I would expect the 7805 to get too hot to touch. If you are actually drawing 300 ma, the 7805 will be over the maximum and may shut down.

    You might put a 10 ohm, 10 watt resistor between the battery and the regulator input. This will allow much of the voltage drop to be across the resistor instead of the regulator and it will run much cooler.

    Mike
     
  20. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi,
    Get some old multi core telephone wire,from the local scrap yard, its ideal for project boards.
     
  21. AtomSoft

    AtomSoft Well-Known Member

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    I Use ethernet cables since i can get them for $2 each 6ft long with 4 pair wire so thats the equivalent of 48 feet. Not alot but comes in hand when im broke :D

    The trick i do is to solder the wire to pin headers and make single and double even quad wires. Its nice and plugs in GREAT!.

    Resistance on wire is not much if nothing. About 0.1 ohms. I think less tho. Lets just say my reader reads .2 with nothing and .2-.3 with the wire so it has to be practically nothing :D
     

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