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Power Distribution Board help needed. — Parallax Forums

Power Distribution Board help needed.

NWCCTVNWCCTV Posts: 3,629
edited 2012-10-30 06:03 in General Discussion
I would like to build something similar to this: http://www.amazon.com/Logisys-PD-10-10-CHANNEL-12VDC-DISTRIBUTION/dp/B004X7UBSM

However, I may want to input up to 48VDC. What I need help with is determining the parts needed and a schematic. For now, I just need to know what to start with to be able to output 12VDC, 9VDC and 5VDC. I will just be experimenting with different values for now so I am not too concerned about input or output amps. I have plenty of capacitors, resistors, voltage regulators, diodes etc that I can use but I just need a starting point such as what to put where to drop the input down to said 12v, 9v and 5v. I will be bread boarding everything and if this could be done using a stamp I am not against doing that.

Comments

  • kwinnkwinn Posts: 8,697
    edited 2012-10-29 17:51
    With up to 48VDC in and 12, 9, and 5V DC out you need to go with switching regulators unless the output currents are minuscule. Otherwise you will end up with a room heater.

    You need to come up with a min/max for the input voltage range and output currents for each of the supplies before you can get any useful help or suggestions. Start by outlining what each output will be used for.
  • NWCCTVNWCCTV Posts: 3,629
    edited 2012-10-29 18:52
    I understand this. I am just trying to get a feel for this by practicing. So, Say I have a 12V Input and I want to output a couple 5V and 9V. I just need to know what I need to do this. Like I said, I am just going to bread board and practice some. This is not going to be put in to anything until I have it down. I know I need voltage regulators but do I also need capacitors and resistors? Once I am able to do this then I can figure out which components I need for various voltage/amperage. Does this make sense?
  • kwinnkwinn Posts: 8,697
    edited 2012-10-29 20:38
    If you have 12V in from a regulated power supply then it is 12V +- a little (0.5V typical). If it is from a 12V battery then the input voltage can be as high as 13.8V (or even higher when charging). You need to keep that in mind when selecting the 9V and 5V regulator. Lets assume you are using a battery, the device it is powering is on while the battery is charging, and you want 0.25A at +9V, 0.5A at +5V, and you want to use linear regulators. You also have a charger that never lets the output voltage go over 13.8V.

    At 13.8V in and 9V out the 9V regulator has to drop 13.8V - 9.0V = 4.8V. The power dissipated would be 4.8V x 0.25A = 1.2W. It needs a heat sink to do that.

    The +5V regulator would drop 13.8V - 5.0V = 8.8V. Power dissipated would be 8.8V x 0.5A = 4.4W. Needs a bigger heat sink.

    You could use the 9V as input to the 5V supply so the 5V regulator would dissipate 4V x 0.5A = 2W. Problem is the 9V supply now has to provide 0.75A so it would dissipate 4.8V x 0.75A = 3.6W.

    The power dissipation across the regulators increases linearly with the input voltage and current. This is why I suggested a switching regulator if you were using higher input voltages and currents. They are much more efficient.

    You will need capacitors for the power supplies and you will need resistors if you use adjustable regulators. Fixed voltage regulators do not usually need resistors.

    You may want to consider separating the regulators from the power distribution board so you have some flexibility in where you place the regulators. V+in and V-in go to connector strips on the distribution board and from there are wired to the individual regulator boards. The Vout from the regulators each come back to their own connector strip that feeds the rest of the system. Makes for a smaller distribution board or allows space for things like fuses and indicator leds. Also makes it easier to swap power supplies.
  • idbruceidbruce Posts: 6,197
    edited 2012-10-30 06:03
    NWCCTV

    There is a very wide variety of power supplies, and each application that requires power, also requires some serious thought pertaining to the power supply. In other words, power supplies should be designed with the end application in mind. If you just want to experiment a little with low voltage and low amperage stuff, then I would suggest taking a peek at the suggested schematic for the Propeller DIP Plus Kit which is attached below and also available in Propeller Education Kit Labs, which can be found here:
    Additionally, most of the datasheets for voltage regulators, include a schematic for typlical applications. So pick a voltage and amperage that you want to experiment with and find a voltage regulator to match your criteria. The datasheet for that particular voltage regulator should tell you exactly how to hook it up for typical applications. You can also find an exhorbitant amount of information by googling "power supply" and "schematic". By doing so, you will find a very wide variety of power supplies that you can build and experiment with, in all kinds of voltages and amperages.

    Bruce
    regulators.jpg
    600 x 212 - 20K
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