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Thread: Power supply (need schematic)

  1. #1

    Default Power supply (need schematic)

    Hi everyone,


    I am about to start work on a MDP for my HSC however for this project I need a power supply with the following ratings;

    Input: 240V (AC) ~ 50Hz (Australian power outlet)
    Output: 24V, 12V, 5V and 3.3V DC
    (basically a computer power supply but with 24v as well)


    24v for solenoids
    12v and 5v for various electronics
    3.3v for propeller


    Does anyone have a schematic on hand or know of somewhere online that could help me with building such a powersupply.


    Thank you

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  2. #2
    Cluso99's Avatar
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    What current do you require at each voltage?
    Do you really need 24V solenoids?

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  3. #3

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    If I can find a 12v solenoid than yes.

    For the currents I am not sure but I can guess;

    12v - 1A
    5v - 1A
    3.3v 500ma

    I have included a diagram below to show what needs power.
    12v - valve, fan
    5v - PIR sensor, 3.3v reg at end of 10m cord for propeller
    3.3v propeller, valve control circuit




    Thank you

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  4. #4

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    12V solenoids are _fairly_ easy to obtain. (see Automationdirect.com.au, and check out their valves such as the N701). Even Jaycar/electus sell 12V Solenoids.

    Might cost you $20 for the solenoid, but IMHO you would save that by not having to build a power supply.


    Hope that helps...

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  5. #5

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    I could always just use an ATX power supply but I think that would be overkill for a single valve, a sensor and two props.

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  6. #6

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    An ATX power supply might be the least expensive way to go if the circuit draws enough power for the supply to operate. Most of these supplies have minimum current draw requirements on the 3.3 and/or 5V supplies.

    If the power requirement is low you may want to use a simple linear supply. I have attached a block diagram of what I use as a starting point for such a supply. This is not a complete schematic so you will need to add electrolytic capacitors on the outputs from the regulators and small (0.1uF) ceramic or similar caps to the input and output of the regulators.
    Last edited by ForumTools; 10-02-2010 at 03:12 PM. Reason: Forum Migration

  7. #7

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    There are a number of sites that show how to convert a computer power supply to a bench power supply. The general idea is to use a 10 ohm 10 watt resistor across the 5 volt wiring to keep it going. Do a web search on 'convert computer power supply' and you should find several leads. Here is the first I came up with http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply , but there were others. If you have a supply that puts out -12 volts, then you can get your 24 volts between the +12 and -12 volt connections.

    Ron
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  8. #8

    WBA Consulting's Avatar
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    It's overkill and a bit pricey, but I have a Condor GPC80PG Power Supply sitting on my desk that was scavenged from a JOT conveyor system that was wired for use in the UK. It would give you everything you need except the 3.3v (which can be done with an LDO off the 5v rail). Mouser lists it at $140 under part number 675-GPC80P-G.

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  9. #9

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    kwinn,

    Would a
    9V - 24V, 60VA, 5A Multi-tapped Transofmrer be alright for that curcuit if the 24v regulator was 12v?


    Thank you

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  10. #10
    Cluso99's Avatar
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    If you are not using a commercial power supply (as in PC) then wouldn't it be safer to use a power pack. Say 12-15V @2A and regulate from there. Saves all the legal and safety issues of 240V connection.

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    Home of the MultiBladeProps: TriBlade,RamBlade,SixBlade, website
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    Prop Tools under Development or Completed (Index)
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    Search the Propeller forums(uses advanced Google search)
    My cruising website is: www.bluemagic.biz MultiBladeProp is: www.bluemagic.biz/cluso.htm
    Last edited by ForumTools; 10-02-2010 at 03:12 PM. Reason: Forum Migration

  11. #11

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    I would have to strongly agree with Kwinn I get ads sent to me from surplus places I subscribed to, an AT Power supply with +12V +5 volts 240Watt is only $9.00 dollars I have one I took apart and converted to bench power as sailman has suggested and now have +5 +12
    and +24 I tapped off the circuit board . I also found found a negative 9V tap but have never used it other than measured with my meter. Also I am in the USA and feed it 110V
    Last edited by ForumTools; 10-02-2010 at 03:12 PM. Reason: Forum Migration

  12. #12

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    Regulating the 24V input down to 12V with a linear regulator would dissipate a lot of power, probably more than a 3 terminal chip could handle if the current was more than a few mA.

    Can you post a schematic of the transformer windings/taps?
    Last edited by ForumTools; 10-02-2010 at 03:12 PM. Reason: Forum Migration

  13. #13

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    @kwinn: (PS1.bmp) are you sure lm7812 is a 24v regulator?


    I also agree with Cluso99 legal/safety issues considerations.


    @ComputerGuy: Have also a look at www.recom-international.comor download the catalogue


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    Last edited by ForumTools; 10-02-2010 at 03:12 PM. Reason: Forum Migration

  14. #14

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    After reading everones comments I have decided to go with an ATX power supply, this will make case design a bit more challenging but will remove the stress of having to design my own power supply and is also cheaper.

    Thank you all for your comments and suggesttion.

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  15. #15

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    @computer guy

    Good choice. I use them quite often and they work well. Designing the case to fit the power supply and your circuit is probably less work than designing a power supply.

    @dMajo

    My apologies for the error. I have been doing this so long I sometimes forget that not everyone is familiar with these generic parts.
    An LM7812 is a 12V regulator. As mentioned in the post with the diagram, it is more of a generic circuit used as a starting point for a simple linear power supply. I will use different values of components (ie 24V ct xfmr, 7805, 7812, for +5 & +12V) for different output voltages. I am so familiar with this simple supply that I do not change values on the diagram and did not notice that the output from the LM7812 was marked as +24V.
    Last edited by ForumTools; 10-02-2010 at 03:12 PM. Reason: Forum Migration

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