Should've been h-bridge, ended with touch/wind/sound sensor

Discussion in 'General Electronics Chat' started by redacejr, Jun 3, 2008.

  1. redacejr

    Thread Starter Active Member

    Apr 22, 2008
    85
    0
    i was planning to do this circuit as an h-bridge with a l293
    http://www.toddholoubek.com/classes/pcomp/hbridge/Hbridgel293.html

    ... but something went horrible but surprisingly wrong!!!:mad:


    i set up the circuit as shown and instead of the arudino i decided to use a low frequency schmitt trigger
    as soon as i set up the circuit for the l293 i had to ground one of the wires ( shown yellow in the tutorial) and so i used a coil of wire i had next to me and anchored it to the desk ( i dont know id thats even called grounding lol)...... while i was looking for a dual 556 timer i started whistling ( i like to do that haha) but the unexpected happened!!

    i heard buzzing coming from the gearbox :( so i investigated for shortages... after some messing around i noticed that if i whistle,speak in high pitched voice,touch or blow into the coil the motor goes round at full speed... :eek::eek:

    wt did i do wrong??
    i had not connected any of the 2 other colured wires that are connected to the arudino, no other passive components , just the l293, bridge wires, 5v supply , motor and coil
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    No, that's not coming close to grounding the line. The input is floating, and conducting noise into the uC, which causes the odd behavior.

    The wire needs to be connected to circuit ground for proper operation.
     
  3. redacejr

    Thread Starter Active Member

    Apr 22, 2008
    85
    0
    wt u meen by grounding tho... connected to 0v or connect the thing to a metal fence or bury it???.... the ground is my fault???:eek:
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Circuit ground is "0V". Earth ground is a few metal stakes or pipes in firm contact with Mother Earth. A metal case is just a hunk of metal, unless and until it is connected to "0V" or Earth ground.

    Note that I am putting "0V" in quotes. I refer to the circuit connection name, not to some voltage measurement.
     
  5. redacejr

    Thread Starter Active Member

    Apr 22, 2008
    85
    0
    i went a step ahead. beacause i DO NOT have the arudino microcontroller board i need asystem for my project. i did the whole thing but instead of the yello and blue wired shown in the tutorial i attached 2 metal plates... when you touchone the motor turns one way and when you touch the other it turns the other way.... maybe because of earth grounding or perhaps because of the mA in my nerve system .... is there a possible way toset up a system consisting of 2 LDRs so that trhe motor changes direction according to the suns position????
     
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