Increasing amperage in a 12 volt DC circuit without transistors or additional power supplies

Discussion in 'Electronic Projects' started by Honoguy, Nov 14, 2017 at 6:53 PM.

  1. Honoguy

    Honoguy

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    I'm using a 12-volt DC circuit where the 555 IC puts out 150 milliamps and I need to increase that to 350 to 400 milliamps. Please Supply a simple circuit using the output from the 555 pin and the 12 volt power supply along with a mosfet to get me the 350 milliamps that are going to drive my DC motor which requires 12v and 350 milliamps. I do not wish to use a transistor to boost amperage as heat might be a factor and don't want to use heat sinks to complicate things. The whole project is using a pack of 8 double-a cells. the original circuit can be found on this link however I do not want to use a relay or additional power source.
    https://www.homemade-circuits.com/simple-automatic-plant-watering-circuit/
     
    Honoguy, Nov 14, 2017 at 6:53 PM
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  2. Honoguy

    kellys_eye

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    Use a MOSFET then.

    You can't increase the output capability of the 555 without using an external buffering device (transistor, MOSFET or, indeed, a relay).
     
    kellys_eye, Nov 14, 2017 at 8:21 PM
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  3. Honoguy

    BobK

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    A MOSFET is a transistor. Metal Oxide Silicon Field Effect Transistor.

    Connect the 555 output to the gate, optionally through a 10Ω resistor. Connect the motor - to the drain. Connect the source to ground.

    Make sure you use a MOSFET that is fully turned on at the output voltage of the 555, which is a couple of volts less than the supply voltage.

    Bob
     
    BobK, Nov 14, 2017 at 8:25 PM
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  4. Honoguy

    Honoguy

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    I will get about 150 ma out of 555. Which MOSFET will get me at least 350 ma to run submersible pump?
     
    Honoguy, Nov 15, 2017 at 2:07 PM
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  5. Honoguy

    kellys_eye

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    You don't seem to understand the principles - basically you will be using the MOSFET (transistor) as a switch.

    When the switch is connected and activated (as per @BobK post above) the MOSFET will pass (carry) whatever current the load demands. If your pump requires 350mA then that's what will flow.

    Note - your power supply MUST be capable of DELIVERING the current as well. You can't manufacturer current from nothing, it must be there in the first place and you are using the MOSFET (via the 555) to control that current.
     
    kellys_eye, Nov 15, 2017 at 2:46 PM
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