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Re: Arduino – Attiny84

Discussion in 'Microcontrollers, Programming and IoT' started by GeoffC, Jul 28, 2013.

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  1. GeoffC

    GeoffC

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    Mar 11, 2013
    Please can someone help me regarding power consumption of ATtiny84 chip?
    Will a ‘100 m/a 5 voltage regulator’ (TO92) be sufficient to supply a ATtiny84 chip (14DIL) with 4 output pins 5,6,7,& 7 as PWM ???
    The Attiny84 will (I hope), control 4 independent 12 volt Fans through a ‘IRIDL014 MOSFET’.
    I need to tap-off 5 volts from the 12 volts supply to run the tiny84 chip
    Please can someone help me, as I am making up a printed circuit and need to have it right. (First time!!)
    Regards, Geoff.
    E-mail: [email protected]
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    Last edited: Jul 29, 2013
  3. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

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    Nov 28, 2011
    Yes, probably. It depends how much current you will be drawing out of the ATtiny84's outputs, since the device itself doesn't draw much current for its own operation.

    You should limit the gate current drawn by the MOSFETs by adding a series resistor. For example if the ATtiny is rated for 20 mA maximum current per output, use R = V / I where V=5V and I=0.02A so R=250 ohms. So use a 270 ohm series resistor for each gate. Use plenty of decoupling capacitance (10 uF or more) on the 5V rail to supply these current peaks.

    You need to calculate the continuous load current for anything else you drive continuously, such as LEDs or transistors, and add that to the device's consumption, to get the total load current on the regulator.

    Also consider the regulator's power dissipation. At 100 mA and dropping 12V down to 5V it will dissipate 0.7W so it will get fairly hot.
     
  4. GeoffC

    GeoffC

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    Mar 11, 2013
    Thank you for your answer, it was very helpful. I had cold feet relying on 100 m/a. From your answer I feel I would be sailing too close to the wind. So I will be redoing my circuit, using a 5 volt 500 m/a V/Regulator. Regards, Geoff.
     
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