Repost: Power Supply

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This topic contains 1 reply, has 1 voice, and was last updated by  akiba September 11, 2017 at 2:48 pm.

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  • #488

    akiba
    Keymaster

    [Reposted from old forum]
    I am trying Freakduino LR to receive 4 pwm signals over wireless and using L298 motor driver to run 2 motors back and forth like simple RC car.
    Freakduino receives signal and shows on serial port properly without L298 motor driver attached.
    But if i hook up the L298 to Freakduino like 4 input pins and 1 GND, Freakduino stops receiving any signal.
    I guess, it must be a power supply issue. I am using laptop USB 5 V. probably current is 0.5 Amps.
    Datasheet clearly says I can use 6V to 14V using DC adapter. currently I do not have that kind of dc adapter.
    Question is,
    i. .Could I use 5V 2Amps instead, using USB cable from the mobile power bank?
    ii. If i use 12V DC battery, what should be the Currnet / Amps limit?

    Akiba
    FreakLabs Open Source Wireless
    Twitter: @freaklabs
    Facebook: https://www.facebook.com/freaklabswireless

  • #489

    akiba
    Keymaster

    I think the first thing to check is the 5V and 3V voltage after you connect up the L298. It might be pulling so much load that it pulls the voltage out of spec. The next thing to check is if it throws a lot of noise into the system. The RF front end on the long range boards pull a lot of current and if you’re simultaneously driving a motor, it could be affecting the power supply of your source. You may need to beef up the power supply. A 12V adapter would make the 5V regulator really hot since all the excess voltage (7V) would get turned into heat. I wouldn’t recommend it. Instead, I’d use as low a voltage as possible. Even 5V would be fine. Technically, I say 6V input because there’s a 0.8V dropout needed for the 5V regulator. If you use a 5V adapter, then the output voltage would be around ~4.5V or something due to the dropout (its nonlinear). That shouldn’t affect operation though but make sure the adapter can supply enough current for the motors as well as the RF front end.

    Akiba
    FreakLabs Open Source Wireless
    Twitter: @freaklabs
    Facebook: https://www.facebook.com/freaklabswireless

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