12v to 5v converter?

RontopiaRontopia Posts: 139
edited July 2007 in Robotics Vote Up0Vote Down
hi all.

I have done some searching on this forum and have found nothing on the subject. so Im at your mercy..

I have this base http://www.lynxmotion.com/Category.aspx?CategoryID=57·and a·propeller with a bunch of sensors and stuff. ok now my question or need for input is for power. at first I thought I would want to run this whole thing from a 12 or 14v rechargable battery.· I was looking into a dcdc converter that would give me 12/14 volts in and 12/5/3.3 volts out.. but then I realized that i only really needed 5/3.3 volts out .. and then i got to thinking that I really only need 9volts out because the prop I have is the education board which has all the proper power convertion parts..

so my question is .. what do you think? I will have 12v coming from·2 6v Ni-HM 2800 mah battery packs.·can I power the education kit with this same battery..· or would you just use a 9v and to power sensors and prop, and use the larger battery just for motors?

another·option is to use the power lead from the center of the 2 6v batterys to power·the prop and sensors?

another option is to use a converter like I wrote about above.

opinions please?



IC layout designer
Austin Texas


  • 6 Comments sorted by Date Added Votes
  • D FaustD Faust Posts: 608
    edited July 2007 Vote Up0Vote Down
    I think you should probably power them separately becuase the motors do cause amperage spikes. Just make sure to connect the grounds (I'm no expert, but I read about this somewhere on this forum)

    D Faust
  • John R.John R. Posts: 1,376
    edited July 2007 Vote Up0Vote Down
    I'd like to jump on this thread too. I have a robot application (see the link in my signature for the build log) that will need a 12 volt power supply for the camera, 7 volts (or so) for the servos, and 5/3.3 for the electronics (Prop and other sensors, some 5 volt).

    I'm under the impression that just putting in voltage regulators is not the most efficient way to drop the voltage, and results in excess heat. I'm less concerned about the 5/3/3 volts for the electronics, but am concerned about the current draw, and resulting heat loss from 18 high torque robot servos.

    I'm not an EE, but have heard terms like DC/DC converters, switching power supplies, and others used in this type of application. What is the difference, where do we find these things, and how do we determine what is the best choice for a given application?

    John R.
    Click here to see my Nomad Build Log
    John R.
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  • RontopiaRontopia Posts: 139
    edited July 2007 Vote Up0Vote Down
    so I have been reading and reading today. here is a website that helped me out a little



    IC layout designer
    Austin Texas
  • LawsonLawson Posts: 870
    edited July 2007 Vote Up0Vote Down
    you'll have to look at the data sheet for the Linear regulators used on your Prop board, but it should be fine running from 12-14 volts. It WILL get a lot warmer though. If you need a lot of power on the 5v/3.3v buses then I'd recommend getting a switching power supply to step the voltage down.

    @John R.: linear regulators act like automatically adjusting resistors. They automatically adjust to maintain the output voltage and waste any extra input voltage. Switching regulators are more akin to a lever or set of gears. They use active electronic circuits to trade voltage for current or current for voltage. This allows a switching regulator to operate at high efficiency even with a large difference in input and output voltage. This high efficiency is what makes them most suitable for use with heavy loads.

    Good Luck,

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  • Mike GreenMike Green Posts: 22,601
    edited July 2007 Vote Up0Vote Down
    Your 1st choice would be to use a switching regulator to step down the 12-16V to the regulated 5V that your board can use. If you want to use a dual output switching regulator, you could use both a 5V and 3.3V output, but there's not much power lost in using a linear regulator for the 3.3V supply. If for some reason you want to use both on-board linear regulators, you could use a switching regulator that puts out anywhere from 6V to 7V. The regulators are low dropout types and would be happy with 6V and there would not be a lot of power lost if you ended up with 7V.
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