Solderless Breadboard power supply

Discussion in 'The Projects Forum' started by Dr.killjoy, Jun 3, 2013.

  1. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
    1,190
    156
    I want to build a Power supply for my solderless breadboard and I know that they sell them on ebay but my is retarded and has one power rail ... I will be posting up my schematic later and would like some input for it because this will be my first circuit build ..

    My specs
    Input- 12V DC
    Output voltage -
    12V DC
    9V DC
    6v or 5v DC
    3.3V DC
    Amps- 1 amp or less
    Poly fuses used
     
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
    3,869
    1,393
    Are you planning one power supply that is switchable between these voltages, or that is capable of supplying all the voltages simultaneously?
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    My favorite is to just rescue a computer PSU from its journey to the landfill. Cheap or free, you can even be paid to take it away. Any PSU has ±12V, +5V and maybe other voltages available. Cord, fuses, enclosure, built-in protections. It's crazy to build your own.
     
  4. bance

    Member

    Aug 11, 2012
    315
    34
    Jason I'd probably make one for each voltage, they'll easily fit on about 1-1 1/2" square vero-board, you can use pin headers to plug them straight into your breadboard... you'll probably need heat sinks for the lower voltage regulators if they have to be run from 12 volts DC.

    All the best, Steve.
     
  5. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
    1,190
    156
    There is a pic below to show the breadboard I am talking about..
    Well the power will come from a wall wart and go to the board from there and the input voltage can be change too .. But I want to use some auto reset fuse and use header pins in order to choose what voltage I use so one circuit will be running instead of all of them .. I plan on using vero-board and hard mounting it to the plate of the breadboard...


    [​IMG]
     
  6. Shagas

    Active Member

    May 13, 2013
    802
    74
    What you could do is find a PSU that gives 14 volts or more (laptop power supplies or wall-warts)
    And use Voltage regulator Ic's to give you the voltages that you need. Or use a LM317 adjustable . I think you can put many of them if you want simultanious sources with diffrent voltages

    Just don't forget that if you are going to use voltage regulators then the input has to be at least a certain amount of voltage higher than the output (dropout voltage) . I don't know the exact numbers but some of the regulators have a 0.7 volts or 1 volt or 2 volts which means that if you want 12 volts with a regulator then the supply has to be preferably 14 volts (maybe the more experienced members can shed some light on that)
     
  7. bance

    Member

    Aug 11, 2012
    315
    34
    Here's the sort of thing I used before I got my bench supplies.

    An adjustable unregulated wall wart and various regulator boards.

    Maybe just try to make a 5 volt board to start, then you can get adventurous, adding in crowbar circuits or dual supplies, whatever!

    HTH Steve.

    PS. the coin is a 10 pence piece (about the same size as a US. quarter dollar)
     
    Last edited: Jun 3, 2013
  8. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
    1,190
    156
    Also can you stack Standard voltage regulators into limit the heat output ???



    That's kind of where I was going but has to fit on a small board with a bit of protection..


    I am starting with a lm 317 and working from there..

    I have a nice size mastech power supply at home but my problem is that my work bench is my kitchen table so the stuff has to go away when every I am done and I really hate hate dragging it out every time I need power up something..
     
    Last edited: Jun 4, 2013
  9. Shagas

    Active Member

    May 13, 2013
    802
    74
    Well size is going to depend on how much current you will be needing .
    I think that you can put several voltage regulators in series to ease the load , but how much current do you need?
    An LM317 provides up to 1amp I think but don't forget to put a nice heatsink on it with some paste in between
     
  10. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
    1,190
    156
    I am working with small circuits like 555 timer and leds and stuff like that ..
     
  11. Shagas

    Active Member

    May 13, 2013
    802
    74
    Well in that case one LM317 will be more than enough but still don't forget to slap on a heatsink .
    Just buy a transformer that will give you an output of 14volts (don't get more than that because then the LM317 will need to dissipate more heat )
    And use the regulator to give you the voltage you need.
    GOogle Lm317 circuit or something like that and you will find how to connect it so it gives you an adjustable voltage output.

    Also google : how to make a workbench or breadboard power supply . It's pretty simple.
    Transformer -> bridge rectifier (or make your own with diodes) -> Filter capacitors -> voltage regulator and voila!

    Just make sure that the transformer you are getting supplies at least 200mA , should be a relatively small transformer.
    Also check out torroidal transformers , they are abit smaller I think and more flat but more expensive
     
  12. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    A better approach would just be a fixed resistor rated to the proper heat dissipation. For instance if you need to drop a total of 10V at 1A to get to your regulated voltage, drop 6v across a 6Ω resistor and then let the regulator drop the remaining 4V. The resistor would be dissipating 6W in this scenario, so you'd want one rated to 10-15W or more to be safe.
     
  13. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
    1,190
    156
    Here is what I have so far
    But have to figure out how to lower voltage to 5 V for relay.. But my point to all this is to have basic but idiot proof power supply ..
     
  14. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    The 3 diodes on the right. 2 are backwards. The 3rd one, below the relay, what's that for? What does the relay accomplish that is not accomplished by the power switch on the left?
     
  15. Shagas

    Active Member

    May 13, 2013
    802
    74
    I can't understand what all those diodes are there for . I'm guessing you are putting them there with the notion that if you connect something backwards then it won't damage your regulator . Well you might damage your components but not the regulator. Also If you want to make it idiot proof then just put a current limiting fuse .

    I think connecting it like this is more than enough

    http://www.circuitstoday.com/few-lm317-voltage-regulator-circuits
     
  16. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    Well, the reverse polarity diode on the relay is valid - if the relay needs to be there at all, which I don't see - to absorb the emf pulse when the relay field collapses. And the one around the regulator protects it against a power outage which is almost guaranteed by having that power switch in there. That diode bleeds off the energy stored in the output capacitor. The LEDs are for show, which is valid. But that still leaves 2 diodes that I see no need for.
     
  17. Shagas

    Active Member

    May 13, 2013
    802
    74
    Ah yes the one across the regulator is for power outage, thx
     
  18. Dr.killjoy

    Thread Starter Well-Known Member

    Apr 28, 2013
    1,190
    156
    Sorry for any mistakes because my sons was rushed to the hospital and we are finding out my 3yrs old is a type 1 diabetic and still is in the hospital and my head is not in the game ..

    But anyways The relay is for reverse protection but the problem is that this is a adjustable voltage regulator not fixed voltage is I can figure out to make the relay work through out the voltages .... The diodes are for protections are as per the lm317 datasheet listed below..But the result for me was to delete the relay circuit and add a resettable fuse with a resister and led as a fault indicator ..


    http://www.onsemi.com/pub_link/Collateral/LM317-D.PDF
     
  19. wayneh

    Expert

    Sep 9, 2010
    12,103
    3,038
    Sorry to hear that, but if it's any consolation, there are few things as well understood and treatable. He's lucky to live in a time with so much hope for ever-better treatments and even a cure in the wings. My step-grandmother lived to a ripe old age with diabetes in the days when that was so very unlikely. A challenge, yes, but one that can be met. Good luck. ;)
     
  20. bance

    Member

    Aug 11, 2012
    315
    34
    Hey Jason,

    Sorry to here that your child is not well, but as wayneh say's, medicine has come on leaps and bounds. I hope all will be well with you and your family.

    Best wishes, Steve.
     
Loading...