556 dual circuit help

Discussion in 'The Projects Forum' started by guitarplayer598, Feb 24, 2012.

  1. guitarplayer598

    Thread Starter New Member

    Feb 24, 2012
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    0
    I need some help with a 556 circuit. I am kinda new to this stuff. I am trying to build a circuit to move a motor in one direction for a few seconds (switch in up position) and a whole different circuit to move the same motor in the opposite direction for a different amount of time (switch in down position). So I wired it all up and soldered it together but one circuit is completely dead and the other is continuously on, I tested it after i soldered it with LED's and one LED never comes on and the other stays on. So my first question in my troubleshooting is can I wire all grounds together for both circuits to one wire? also can I do the same for the power wires. Will this cause trouble?
    Many thanks in head of time.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,052
    3,244
    Yes. All grounds must be tied together, both circuit and power.

    Post your circuit diagram.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    If you have more problems show us your schematic, they are the language of electronics.
     
  4. guitarplayer598

    Thread Starter New Member

    Feb 24, 2012
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    0
    Here is my schematic I jotted down for this circuit and sorry it's a bit sloppy.
    Thanks again
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    If you store your files as a .gif or .png you will find you can do more with them on a site like this.

    [​IMG]

    Before we get too deep into the schematic lets talk about the motor. What are it's specs? Voltage and current is the thing.

    A quick side note about 555/556's. You can only pull 0.2A from the output of a 555, and it will not quite be at the power supply levels. The positive side looses around 1.2VDC due to the particular 555 configuration. What this means is you are going to have to use drivers, reduce the motor voltage specs, or raise the power supply voltage. Or some combination of the 3.

    I pulled this illustration out of my LEDs, 555s, Flashers, and Light Chasers article.

    Chapter 4 -The 555 Integrated Circuit


    [​IMG]
    .................................................. .......Figure 3.1
     
  6. guitarplayer598

    Thread Starter New Member

    Feb 24, 2012
    3
    0
    Thanks for the help, The motor is 12v dc and the full load current is 0.73 A. I have a couple of tip 120 darlington transistors for a motor driver 1 for each circuit. Would this transistor work for this circuit and motor, also how would I calculate the value of the resistor needed in between the chip and the transistor?
    Thanks again for the help with this.
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    A BJT (bipolar junction transistor) is not actually the best part for this.

    A conventional transistor as described about needs about 1/10 the base current as what goes through the collector.

    I think I would use relays, but let me do some research on older threads here.
     
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