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Power supply — Parallax Forums

Power supply

computer guycomputer guy Posts: 1,113
edited 2007-01-18 05:42 in General Discussion
I am looking at making a power supply for my robot with 24v in to it and 5x 5V out and 5x 12V out.

Is this ok or do you think it needs changes.

(Pictures attached)

Post Edited (computer guy) : 1/15/2007 6:32:34 AM GMT
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Comments

  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-01-15 01:50
    Hi computer guy, that is nicely laid out, is it not possible to use just 1 12V and 1 5V regulator?

    Jeff T.
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-15 01:54
    That's why i asked i was not sure if it could be done or not but thanks will change that.

    Will save on parts that's for sure.

    Thanks
  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-01-15 02:05
    It will make the PSU more compact too, I would probably fuse each regulator separately also. The damage may be done by the time the fuse pops but it would help localise a problem a little faster and reduce the total possible current flow to the circuit from the 24V.

    Jeff T.
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-15 02:08
    On the outputs of the regulators or the inputs.

    The leds on the psu where there to isolate a problem.

    Thanks
  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-01-15 02:23
    The way I was thinking is say each regulator is rated 5A I would rather have two 5A fuses on the input of each regulator·than one 10A fuse feeding both, with just the one fuse the possible fault current is doubled. Im no expert cg its just how I would do it.

    Jeff T.
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-15 02:28
    Is this what you mean.




    attachment.php?attachmentid=45009
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  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-01-15 02:36
    Yes that looks good to me so more compact, like I say I am not an expert at design but I would look into the regulators, some require aditional components, like caps and resistors and such. You quickly whipped up the design what software is that?

    Jeff T.
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-15 02:42
    Eagle 4.16r2 Light

    Realy easy to use.

    Thanks for your help.
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-15 04:51
    Should i be using 2 12v batteries in series or parallel to go to the psu?

    What fuses would i use (look at schematic above) with these batteries -

    www.jaycar.com.au/productView.asp?ID=SB2482

    and these regulators -

    www.jaycar.com.au/productView.asp?ID=ZV1505
    and
    www.jaycar.com.au/productView.asp?ID=ZV1512

    One last question

    What diode would i use all i want it to do is protect from reverse polarity.

    Thank you

    P.S I love electronics but only learn little bits on occasion so please if my questions are stupid it's my fault.

    Post Edited (computer guy) : 1/15/2007 5:16:20 AM GMT
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2007-01-15 06:07
    computer guy

    Here is what you are looking for this is an adj reglator 1.5 to 37 volt @ 5 amp case steel can T-03

    ·http://www.digikey.com/scripts/dksearch/dksus.dll?Detail?Ref=5399&Row=536647&Site=US

    Here is a 5 volt reglator @ 3 amps· T-03 can

    http://www.digikey.com/scripts/dksearch/dksus.dll?Detail?Ref=2236&Row=202312&Site=US

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    ··Thanks for any·idea.gif·that you may have and all of your time finding them

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    Sam

    Post Edited (sam_sam_sam) : 1/15/2007 6:24:51 AM GMT
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-15 06:21
    sam what is wrong with my regulators?
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2007-01-15 06:28
    The way I was thinking is say each regulator is rated 5A I would rather have two 5A fuses on the input of each regulator·than one 10A fuse feeding both, with just the one fuse the possible fault current is doubled. Im no expert cg its just how I would do it.

    Jeff T.


    ·

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    ··Thanks for any·idea.gif·that you may have and all of your time finding them

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    Sam

    Post Edited (sam_sam_sam) : 1/15/2007 6:36:53 AM GMT
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-15 06:30
    Thanks might look into getting those localy.

    I live in Australia and don't like paying postage if i don't have to.
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2007-01-15 06:37
    computer guy

    I just gave you those link for Data Sheets and Parts No

    If you use these REG make sure that you use a HEAT SINK with them or they will over HEAT

    If you have a load of more than 200 milamps on them then you will need a heat sink on them

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    ··Thanks for any·idea.gif·that you may have and all of your time finding them

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    Sam

    Post Edited (sam_sam_sam) : 1/15/2007 7:02:42 AM GMT
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-15 07:41
    Thanks will talk to the guys at Jaycar.

    Those links you gave me are to adjustable regulators not fixed and i don't have experience with adjustable regulators.
    So i will need to talk to them and see if they have a fixed regulator.

    Thanks still need the answers to my questions i asked in a previous reply.

    1. Should i be using 2 12v batteries in series or parallel to go to the psu?

    2. What fuses would i use (look at schematic above) with these batteries -

    www.jaycar.com.au/productView.asp?ID=SB2482

    and these regulators -

    www.jaycar.com.au/productView.asp?ID=ZV1505
    and
    www.jaycar.com.au/productView.asp?ID=ZV1512


    3. What diode would i use all i want it to do is protect from reverse polarity.


    Thank you
  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-01-15 18:49
    Hi computer guy, what are the 5V and 12V for and how much current are they expected to draw. If the 5V is for your controller·and sensor power then a 1A or·3A regulator will do. If the 12V is for motor power or relays you might not even need a regulator. If that was the case then you might get away with just one 12V battery.
    Answering the question on connecting the two 12V batteries, in series will give you a 24V battery in parallel will give you a 12V battery.
    The protection diode should be rated to withstand the maximum reverse voltage which would be the value of the battery supply and be able to carry·the maximum expected forward current which is the current on the 5V plus the current on the 12V lines, check the data sheets.
    Before you buy your parts you need to calculate the total current for each power rail, whether they need to be regulated or not and decide what configuration of battery will do the job best.

    Jeff T.
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-15 22:37
    So diode = 24v 17ma cause each regulators Quiescent Current is 8.5ma

    I need to regulate the 12 Volt lines for my motors cause my motor controllers need a regulated 12 Volt source.

    Would one 12 Volt battery be enough to power the PSU? Or do i need 2 in series (24V).

    Here is the data sheet.

    www.jaycar.com.au/products_uploaded/LM7512C.pdf

    Post Edited (computer guy) : 1/15/2007 11:17:04 PM GMT
  • stamptrolstamptrol Posts: 1,731
    edited 2007-01-16 17:50
    Hi gents,

    One thing that hasn't come up here is that if we're really talking in terms of several amps, the pcb trace widths will have to be seriously widened.

    As was mentioned, the motor regulators are going to be smoking hot ( say dropping 12volts at 5 amps = 60 watts !!) This is really a good case where the motors should be run off a battery voltage close to what they need.

    Cheers,

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    Tom Sisk

    http://www.siskconsult.com
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  • computer guycomputer guy Posts: 1,113
    edited 2007-01-16 23:04
    Thanks talked to the guys at Jaycar electronics they said that it can't be done the way i wanted to do it.
    I think i have worked out another idea will post soon.

    Thabk you
  • Paul BakerPaul Baker Posts: 6,351
    edited 2007-01-16 23:11
    Hello Computer Guy,

    What is the total (max) current you need for each rail (5V and 12V)? Is there always a minimum current draw on the 5V rail? Where Im going with these questions is using a computer switching supply may be your easiest route (assuming your application will be near an outlet).

    Im not comfortable with a couple elements of your design, first using 2 12V batteries does not fit well with you intended application. Wiring them in parallel will yeild 12V which isn't enough for the 12V regulators, wiring them in series will produce 24V which is _alot_ of voltage to be feeding to the 5V regulators, 19V will be bled off in the form of heat and is highly inefficient.

    Second it is always best to minimize your part count, it would be much better to use a 5A regulator than 5-1A regulators. I know your in OZ and it's not easy to find parts. Some regulators permit connecting them in parallel, but I saw no mention of this in the spec sheet so I wouldn't try it.

    Are you having the board fabbed or making it yourself? If you are having it fabbed, the decrease in fab cost may offset getting a couple 5A regulators shipped from the states.

    Ultimatley your board will probably work as you expect it to, it's not the most efficient (ie read more battery charges required) but that may not be a high priority for you.

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    Paul Baker
    Propeller Applications Engineer

    Parallax, Inc.

    Post Edited (Paul Baker (Parallax)) : 1/16/2007 11:15:18 PM GMT
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-18 04:09
    Thanks Paul

    I have decided to have 2 regulated 12v batteries (already regulated) one will go to my motor controllers and the other to a 5 volt switching regulator circuit i am getting from the states. The second one will power my sensors and thing.

    P.S can you run the BOE from 5 volts regulated or do i have to put another battery in this thing?

    Thank you all
  • Mike GreenMike Green Posts: 23,101
    edited 2007-01-18 04:54
    The BOE is not designed to run from a regulated 5V supply although it might work. It now uses low dropout regulators which might provide maybe 4.7V to the Stamp's internal circuitry. You could modify the board to power everything off a regulated 5V supply. Look at the schematic for the BOE. This isn't recommended since normally the Stamp uses its own regulator which provides some noise isolation from the rest of the BOE circuitry.

    If your Stamp isn't switching a bunch of LEDs or similar loads (just logic loads), you could run it off the 12V. The main reason for limiting the maximum Vin is the power dissipation in the Stamp's internal regulator (with a 7V drop to +5V times the current drain of the Stamp and it's I/O). You could also just put a couple of series diodes between the 12V supply and the Vin of the BOE. Each would drop 0.7V and take some of the power dissipation. 4 to 5 diodes in series (like 1N4001) would do the work nicely and are pretty cheap and readily available.
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-18 04:57
    Would it be easier to connect a ... resistor to the input on the BOE and notch the voltage down to 9V from 12V or would that not be efficient.
  • computer guycomputer guy Posts: 1,113
    edited 2007-01-18 05:42
    This page seams to suggest that is can be powered from 12V.

    www.parallax.com/html_pages/products/componentshop/power.asp

    Is that true? can the BOE be powered from 12V dc?

    Thanks

    Post Edited (computer guy) : 1/19/2007 6:47:56 AM GMT
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