Critique this

Discussion in 'General Electronics Chat' started by jarwulf, Jan 30, 2014.

  1. jarwulf

    Thread Starter Member

    Jul 7, 2013
    60
    0
    Black has already been assembled. Red I'm planning. Blue, planning but not sure if necessary.

    The addition is to connect ringer to the arduino. A transistor is used to switch the current on. In theory when power is applied to the the first pin of the transistor from the arduino, current can flow from the battery to the ringer circuit.

    PS should I add components anywhere? Such as a resistor in between the voltage booster and ring generator

    PPS change 7V to 9V for battery. Voltage booster can handle up to 11.5V
    [​IMG]u
     
  2. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    Since this device has no stated purpose how can we tell if it might achieve it? What are you trying to do?

    A real schematic would also be useful.
     
  3. jarwulf

    Thread Starter Member

    Jul 7, 2013
    60
    0

    Its a phone. The only thing thats important is if the red and blue parts are not wired to produce damage. And if a resistor needs to be added anywhere (such as in between the booster and ring generator) or a component is unnecessary.

    The plan is to apply current to the transistor from the arduino to allow current to flow from the battery to the ringer.
     
    Last edited: Jan 30, 2014
  4. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    I'd look for a logic-level MOSFET to replace the TIP120 darlington. Either may work fine, but with the MOSFET you have no concern about supplying an adequate base current to saturate the transistor and turn it fully on. You would want a pulldown resistor (e.g. 100K) to pull the MOSFET gate low in the event of a failure to open of the controller. You don't need any resistor between the gate and the control voltage (where your 2.2K is now).
     
  5. jarwulf

    Thread Starter Member

    Jul 7, 2013
    60
    0
    Any logic level MOSFET will do? Where would the pulldown resistor go in the diagram?
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,034
    Pretty much. Get an N-type, rated for at least 3X the anticipated current drawn by the stuff you are switching. The pulldown goes from the gate to ground (or source).
     
  7. jarwulf

    Thread Starter Member

    Jul 7, 2013
    60
    0

    Are you sure about not needing the 2.2K resistor? Would it hurt to leave it in? Also I'm a little confused as to how to put the resistor gate to ground since the gate pin is attached to the control port.

    I'm following http://www.martyncurrey.com/?p=152 and people commenting about it were pretty insistent on having the resistor between the port and transistor base. Here is the revised diagram.


    [​IMG]
    [​IMG]
     
    Last edited: Feb 2, 2014
  8. jarwulf

    Thread Starter Member

    Jul 7, 2013
    60
    0
    Here is a revised connection. Does anybody see any problems with it? If not I will begin laying it out. Just need the confirmation that nothing obvious is wrong.




    [​IMG]
     
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