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Solenoid Circuit Help

Discussion in 'General Electronics Discussion' started by Skyman, Jul 6, 2015.

  1. Skyman

    Skyman

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    1
    Feb 17, 2015
    Wasn't sure whether to post this in "Microcontrollers and Programming" or here so I posted it here as well.I'm new to Arduino and programming so I need some advice. My goal is simple: control a solenoid with an Arduino by using a MOSFET. I'll send a digital signal to the MOSFET, turning it on, allowing high voltage (+30V) to be applied to the solenoid. I'm using a TDK Lambda power converter that converts AC to DC. I'm not sure if my schematic is correct or not. Im confused about the difference between the Ground on the Power converter and the GND (Ground) on the Arduino. Also wasn't sure about the -V on the power converter and whether or not this connection along with the ground connection on the Arduino was correct. Any help would be greatly appreciated. I want to make sure my wiring has no errors. Scan 47.jpeg
     
  2. Minder

    Minder

    2,876
    596
    Apr 24, 2015
    I assume you are powering the arduino separately?
    And if so the power common (-ve) for each supply has to be connected together.
    If that was your question.
    One problem with N.A. terminology, GND (chassis) is also used for (Earth) GND.

    M.
     
  3. Skyman

    Skyman

    22
    1
    Feb 17, 2015
    Maybe the question I'm trying to ask is if it is okay to have the Solenoid Coil going to the Ground of the Arduino. As in, when the Mosfet allows the high voltage to go from its drain to source, is it okay that it will go to the Ground of the Arduino like in my diagram? Is there a limit of voltage/current the Arduino can take for its ground pin? Is this a logical question to ask or is having a common ground (to the Arduino) the right thing to do?
     
  4. Minder

    Minder

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    Apr 24, 2015
    Yes, when combining two separately sourced devices they both require a common reference point, in this case the 0v side of each supply, or GND if you like.
    IOW both supply gnd's are connected. The solenoid current does not flow through the Arduino.
    M..
     
  5. Skyman

    Skyman

    22
    1
    Feb 17, 2015
    Thanks for the reply, I know it was a very novice question but I'm just learning about electronics so any advice will help. In regards to your first reply is yes I plan on supplying the Arduino with another external supply of 5V to its 5V pin. It's my understanding that this external power source cannot surpass 6V or so if connected to the Arduino 5V pin because it is unregulated. Also if I were to use the jack to power the arduino I would need anywhere from 7 to 12V. Just making sure, is this correct? (I don't have an arduino yet but plan on buying one for a pinball machine project)
     
  6. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    As an aside I don't think this is a solenoid or even a DC to AC converter at all. This circuit looks more like a DC relay coil closing a circuit on AC Mains.

    Chris
     
  7. Skyman

    Skyman

    22
    1
    Feb 17, 2015
    Right, the actual circuit doesn't do the converting, a TDK Lambda AC to DC converter does that (like one of these http://www.digikey.com/product-detail/en/LS150-36/285-1815-ND/1918826). My question is: Is everything wired correctly?
     
  8. Minder

    Minder

    2,876
    596
    Apr 24, 2015
    Looks OK, that is a common SMPS .
    M.
     
  9. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    OK, I see now that the AC socket you have there is just the mains input to your Lambda power supply.

    It's good practice (SOP) to place a 10Ω - 33Ω resistor between the output pin of the uC and the Gate of the MOSFET; to reduce ringing.

    FYI: The resistor between GND and the Gate is not a "pullup" resistor. Pullup's connect to the + rail.

    Chris
     
  10. Skyman

    Skyman

    22
    1
    Feb 17, 2015
    Thanks for the advice and the clarification with the resistor. So in my drawing the resistor is considered a "pull down" resistor? Just want to make sure. Also you say that adding a small resistor (10 - 33 ohms) between the gate and controller pin will reduce ringing. What is ringing?
     
  11. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Actually that's a very good question. I've always just called it the "Gate Resistor" or "Gate - Source Resistor". Since the input resistance of the gate is near infinity the resistor can be considered to be a very light load on the signal source supplying the signal. I believe most of us would refer to the series (Anti-Ringing" resistor as the "Damping Resistor".

    Chris
     
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