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ULTRA clean 9VDC Power Supply Project

Discussion in 'Electronic Projects' started by Peter_wadley, Mar 25, 2007.

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  1. Peter_wadley

    Peter_wadley New Member

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    Hi all,

    PLEASE SEE BOTTOM OF PAGE FOR FINAL PROJECT PICTURES

    Here is a small power supply project that I would like to share with all the members of this forum.

    The project is centered on the LM317T regulation chip:

    http://www.national.com/pf/LM/LM317.html

    NOTE: The supply can be configured to any voltage between 1.2 to 37V.

    My reason for building this circuit: In need of a QUIET 9V power supply to power 3 guitar pedals.

    Each pedal is rated @ 250mA making a total load of .75A.

    The LM317t is rated at 1.5A w/ heat sink - making it an ideal choice!

    Please refer to the picture 1-13 as they are called: PIC #xx:

    Ok, Lets get started! :)

    NOTE: Please understand that I have only been practicing electronics for only one year and may do things that other, more knowledgeable, members may see as wrong. This project is for anyone – I have tried my best to make it as simple as possible.

    Please be SAFE!

    Pic#1: Here is the project schematic we will be referencing to

    Tools needed:

    -A ruler, pencil and paper
    -A black sharpie marker
    -Hammer
    -A small punch
    -A drill or DRILL PRESS
    -A set of metal drill bits 5/64 - 1/2"
    -A ziplock baggy or plastic dish
    -A Soldering iron < 35W

    PIC #2: Special Supplies

    -Ferric Chloride Etchant
    -Isopropanol (Rubbing Alcohol)
    - (1) 2 1/2" X 4" blank copper clad board
    -Iron Wool

    PIC#3 Components

    Component List:
    Resistors (1/4 watt rating)
    1 - 270
    2 - 2k
    1 - 6k8

    Capacitors (minimum rating 35 volts)
    2 - 0.1uF
    1 - 10uF
    1 - 470uF
    1 - 1000uF

    Regulator (As requested by Hero)
    1 - LM317

    Other
    1 - 120vac/12.6vac step down transformer

    http://www.radioshack.com/product/index.jsp?productId=2102702&cp=2032058.2032230.2032277&parentPage=family

    1 - power cord
    1 - on/off switch (optional) SPST rated at 3A or higher
    1 - Transistor socket (optional)
    1 - Full Wave 4A Bridge Rectifier
    2 - 1N4002 diodes
    1 - Heat sink for the LM317
    3 - coax power jacks
    22 gauge stranded wire
    Metal Enclosure

    Ok, so we've got all of our materials... lets begin!

    Printed Circuit Board Planning:

    I feel planning is one of the most important processes to consider when creating a circuit.. no matter how simple it may be.

    Using the schematic, visualize what the circuit will look like on the PCB. (Printed Circuit Board) Take into account the SIZE of every component especially larger components such as heat sinks and capacitors.

    Make a few rough drafts of the layout you want for the circuit.

    Something’s to consider:

    -Since the GND of most circuits is the most heavily populated - Border the PCB with the GND track.

    -Always draw to exact scale... even in the rough draft

    -Use the actual components when making the spacing on paper

    Ok, so we have our rough PCB design completed!

    PIC# 4 My Rough PCB Design Draft

    Transferring the rough design to the blank copper-clad board:

    First we MUST clean the board..

    Using the Iron Wool, scour each side of the board.. making the surface rough.
    (30 seconds per side)

    Next, using an all-purpose cleaner - such as comet - lather and rinse the board to ensure it is free of dust and grease.

    The purpose of cleaning the board is to ensure good contact between the ink of the anti-etchant sharpie marker and the copper of the board.

    Now we are going to actually hand draw our rough draft on to the copper board...

    If this is your first time attempting this I highly recommend you make your tracks as wide as possible to unsure no line breaks when etching (As you can see in MINE)

    Also, as pointed out by other members, you can use other, more costly, methods to transfer the design to the PCB.

    PIC# 5: Here is my board with the ink design.

    Now then! We can etch the board :eek:

    Be warned this can get VERY messy and you will most likely loath Ferric Chloride afterwards.

    PIC# 6 My preferred etching setup.

    My method: I place the designed and soon to be PCB into a ziplock bag. Then, using a hook I attach the bag to the wall and add approximately 200ml of Ferric Chloride. I then use tape to add pressure to the bag raising the Ferric Chloride over the highest point of the board.

    The reason I like to do this vertically is because - FOR ME - it is faster. It is faster because the copper sediment falls downwards once dissolved (Compared to horizontal laying in a tray). Please do this which ever way you prefer!

    PIC# 7: Here is my etched board

    You will now see that the black marker ink is still over the copper, don't worry that is a good thing!

    You will now need to use a small amount of rubbing alcohol to.. well RUB off the ink!

    PIC# 8: My cleaned board

    PIC# 9: Punch and Drill

    Now it is time to punch and drill the board. Punching is not required but it does make the drilling process MUCH easier, especially if you do not own a DRILL PRESS. Using your rough draft, punch the necessary holes.

    PIC# 10: Drill Press

    Using a 5/64" drill bit, drill each hole you have punched.

    Once you have drilled the holes you will notice that the exit hole of the drill bit has caused the plastic to protrude out. This can be smoothed out by taking a larger drill bit (I use a 1/4" bit) with your hand and simply turning the head of the bit over the protruding surface. The excess plastic will fall right off if done correctly.

    This is called deburring, thanks HERO.

    The PCB is now completely etched, drilled and ready to go... but first...

    Using my rough draft and a pencil, I like to label where each component goes on the PCB. These label go on the top side.. WHICH IS NOW THE SIDE WHICH HAS NO COPPER.. I say the side with no copper is the top because this is where the components will be sticking out. I use labels to decrease confusion since the PCB is now reversed (when looking at it from the top)

    PIC# 11: Here is my labeled PCB ready to be populated with components.

    Now for the best part! Populating the board!

    Gotta love the smell of solder :D

    When soldering I make the connections in this order:

    1) Resistors (Since they are smallest)
    2) Diodes (same reason)
    3) Bridge Rectifier
    4) LED wires
    6) Capacitors (Since they are so large and raise the board)
    7) LM317T (Transistors, ICs and regulators are not heat friendly! When soldering these always make the solders FAST and wait at least 20 seconds between solders! Use a heat sink if part is expensive)
    8)Transformer leads
    9) Using wire nuts attach a power cord to the PRIMARY 120VAC leads of the transformer.

    PIC# 12: Here is my populated board w/ LED and Transformer

    Before plugging the unit in for the first time:

    -120VAC is EXTREMELY dangerous! Make sure, at all times, you know where the wire nuts between the mains and the transformer are!

    -The wire nuts are for test purposes ONLY!

    -When I make the circuit pretty and assembly it into the metal enclosure I will be using shrink-wrap to ensure the transformer connections are safe!

    -I will also be using a grounded cord, OF COURSE.

    PIC# 13: Here is the power supply plugged in. The LED indicates the circuit is working. The voltage read out is 9.34V.. exactly as planned! The heat sink is also seen in this picture (Big Black Thing)

    - You will see that I have added a fuse on my board. This is not required because the LM317t is thermally protected.

    - LED ADDITION: I have added an ON/OFF green LED indicator which is not on the schematic provided. Simply add a 1000:eek:hm: resistor on the PCB for current limiting then use 22 gauge stranded wire to connect the LED.


    Thanks for reading through my project and I hope you try it out!

    What’s next?

    From here you can either add the coax DC jacks in the 3 open +9 and GND spaces and use the supply.

    OR

    place the circuit into a metal box and then add the coax Jacks

    I will finish this project later this week by assembling it into a metal case and making it pretty and such. I will update the thread when I am finished the project.


    Constructive feedback is always welcome.. no matter how MEAN it may be :D (as you can see by Hero's feedback :D)

    Peter W
    March 25, 2007
     

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  2. gramo

    gramo New Member

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    Way to much reading :p

    But great detail - guess thats what the "Projects" section is for
     
    Last edited by a moderator: Dec 18, 2011
  3. Hero999

    Hero999 Banned

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    The LM317 is not at transistor, it's an IC (Integrated Circuit) which has many transistors, resistors all on the same piece of silicone.

    25V is a bit overkill, I would go for a 12V transformer but you'll probably be alright with even a 9V transformer.

    The RMS input current is just under [Error: Restricted\ command\ found\ (output)] so for an output current of 1.5A it will need to be rated for 2A, for 0.75A it needs to be rated for 1A.

    Did you check the heatsink is capable of dissipating the power witout overheating the LM317?

    Why are there two fuse holders and only one fues?

    You only need one on the input to the transformer (the LM317 is short circuit proof) it should be slow blow and rated for at least:
    [Error: Restricted\ command\ found\ (output)]

    No offence but that doesn't look very professional at all, in fact it's quite messy and untidy.

    Did you know that you can transfer designs from your computer to the PCB by printing them out onto special paper using a laser printer, ironing them onto the board, washing the paper off them etching it? Its called the transfer process and is a lot more easier and accurate than messing around with etch resistant pens. You can buy special paper or you can experiment with magazine paper or photo glossy paper.

    There's also the photo method which involves printing the design on a transparency or tracing paper, putting on top of pre-sensitised board, exposing it to UV light, developing it using hydrogen peroxide then etching it. It's probably the most accurate but you need special sensitised board and a UV lamp box (don't worry you can make this using insect killer or blacklight tubes).

    With the transfer process tracks as thin as 0.5mm are not problem.


    That doesn't sound very safe to me. Are you sure that bag's completely waterproof? What if it falls? I normally use a plactic bowl, it also helps if the etchant is warm, about 50C or 120F is good, some members here have made their own etch tanks, you can also get better etchants than FeCl.

    I see, there is method in you madness, perhaps you should place a tray below the bag in case it spits.

    If you use SMT (Surface Mount Technology) components then you can save yourself a lot of drilling.

    This is known as deburring.

    Bah, 230V is far more dangerous, I've had a couple of shocks and it's never done me any harm.:D

    I'm joking of cours always be careful of AC voltages above 25V (yes you can also recieve a small shock from the secondary of the transformer) and DC voltages above 60V.

    So long as you're aware that this will limit the output current to 1A. You don't need a fuse anyway as the LM317 isn't harmed by short circuits, will shut down then sart working again if short circuited.

    Remember the voltage across the capacitor is
    so that 1000:mu:F capacitor needs to be rated for 40V (the off load transformer voltage is often significantyl higher) or it might explode.

    If you place the circuit in a metal box, always remember to earth/ground the metal enclosure, using star washers and ring tongue terminals.

    No problem, thanks for posting.

    Another thing is r1 needs to be <120:eek:hm: for an LM317, I know the datasheet shows 240:eek:hm:but that's for an LM217 or LM117; don't worry it confuses lots of people.
     
    Last edited by a moderator: Dec 18, 2011
  4. dave

    Dave New Member

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  5. gramo

    gramo New Member

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    critic.com :p

    must be a boring day over there hero999 :eek:
     
  6. Peter_wadley

    Peter_wadley New Member

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    Hero, I will make my reply later in the day... I must take a long nap first :p
     
  7. Peter_wadley

    Peter_wadley New Member

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    Ok nap time is over!

    I copy and pasted the bill of materials he he not my fault :rolleyes:

    RMS = Wah?

    Where are you getting these formulas! I want em! Hero, are you an electronic engineer?

    The LM317 IS getting HOT without the heatsink... do you think If I use the 12.6v (the transfomer is center tapped) secondary I will still get clean 9VDC but without this much heat on the LM317.

    Also instead of the 2K resistors I used 1.5Ks -- Could this potiential be the cause of the heat?

    Is there actually a formula??? I just picked the prettiest one I could find! If there is a formula or process Id like to know!

    Sorry, I meant 2 fuse CLIPS I guess they can be called holders.. one for each side of the fuse :p

    Yes, I know, I am no artist!!

    I know of the two methods you speak of.. but I wanted this project to be for begineers... plus its more fun drawing it out, and besides do the components care if they are sitting on an ugly board?

    No one will see it except me.. its going where the sun dont shine :D

    Better etchants.. Come on thats uncalled for!:eek: I just used the most common solution, seeing has how I see ALOT of people on this forum usually have smaller electronic shops that do not stock a wide variety of products.

    ;)


    What do you mean by this? Isnt SMT just components that can mount on PCBs? Everthing except the transformer? Wouldnt, by using a SMT transformer, you need to drill more holes for the stabilizing pins... plus I dont mind lots of drilling.. drill pressing is FUN.

    [Error: String\ is\ too\ long\ (687, limit 300)]
     
  8. Hero999

    Hero999 Banned

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    Root Mean Square.

    It's the peak AC voltage that does the same work as a DC votlage, 12VRMS will do generate 12W in a 1:eek:hm: resistor and so will 12VDC, the difference is the former will have a peak voltage of 17V while the latter will be continiously 12V. Transformers are always specified in RMS, the output across the capacitor will be equal the transformer voltage times root 2 take the rectifier losses (which you ignore when choosing the voltage rating for capacitors and pay attention to when considering the dropout voltage of the regulator).



    Yes, use the centre tap or use a lower voltage transformer.

    No, the fact that your regulator is disipating so much power is making it hot, reducing the voltage across it will solve the problem.

    This can get complected but it's fairly easy to keep it simple. Heatsinks are specified in temperature rise per watt, the units are normally °C/W. A heatsink with 1°C/W rating will heat up by 1°C for every watt of heat produced by the device, therefore if it produces 10W or heat it will be 10°C hotter than its surroundings.

    Then there's thermal resistance between the semiconductor junction and the package and the package to the heatsink, this is also measured in °C/W you simply add this all on to the °C/W rating ambient and the heatsink.

    Always size your heatsink so the semiconductor junction doesn't get hotter than the maximum temperature rating when it's dissipating the most power and is in the hottest environment you're designing it to work in.

    Lots of information can be found from Google.
    http://www.google.com/search?num=10...rls=en&hs=Eob&q=heatsink+tutorial&btnG=Search

    Well you've posted pleny of pictures of it here on the forum. ;)

    Fair enough SMT isn't for everyone. I often prefer it because not only does it save drilling and space, SMT components can also be cheaper.

    Well if the load pulls more than 1A it will limit the current by failing and stopping th current flow altogether.

    Going back to my point about RMS, this depends on the size of your filter capacitor but if it's large enought to reduce the ripple enough the RMS input current to the rectifier is just under root 2 times the output current.



    You don't need a fuse, the LM317 has built-in over current and short circuit protection for that too. Short circuit it, connect too many pedels and it will limit the current by first reducing the voltage, then shutting down. Disconnect the loads and it will start working again - no need to stock replacement fuses. Also there is a risk the fuse will blow when the power is turned on as a huge current is required to charge the capacitor.

    Not if you reduce the input voltage to something more sensible.

    Yes.

    There appear to be a few things you may have missed from my previous post, no offence intended but please read it again. I know there's a lot to take in and I did ramble on quite a bit.:D
     
    Last edited: Mar 26, 2007
  9. Peter_wadley

    Peter_wadley New Member

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    :p

    I have switched to the 12.6v center tap. The LM317 barely gets hot at all now. I have also, using heat sink compound, installed the the heat sink.

    Ok this circuit is almost done... last Q's

    1) Now that I have changed the to 12.6vAC the fuse blows after about 10 seconds (it is Fast Blow)

    also..

    The fuse is 1.5A did you write this thinking the fuse was 1A or will the 1.5A blow @ 1A because of RMS?

    2) I will be using a 3A 120vac SPST for power on and off.. with changing to 12.6v will this switch be OK to use?

    3) Last question:

    Can heatsinks be so large that they them selfs pull current? Do you mean make sure it is big enough for power dissipation or make sure the heatsink doesnt cause the LM317 to overheat by pulling current it self?

    Thanks again for helping me out Hero
     
  10. mneary

    mneary New Member

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    A suggestion: If the project is to go into an enclosure, you should begin there. It's easier to change the parts locations on the board before you etch it.
     
  11. Hero999

    Hero999 Banned

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    Good, you've solved your first problem.

    You don't need a fuse, please re-read my previous post, I've now highlighted the relevent parts in bold red text.

    No, it's to do with the capacitor drawing a huge current when the power is first applied.

    There shouldn't be a problem but I would put the fuse on the hot side of the mains connection as the lower current will make the switch last longer.

    Lol how can heatsink cause it to draw more current?:D

    All a heatsink does is help transfer the unwanted heat to the surrounding air.
     
  12. Peter_wadley

    Peter_wadley New Member

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    Thanks so much for all your help Hero!

    :) It is much appreciated :)

    I will now read through all the link you have posted as your probably getting sick of these questions :eek:

    Peter W
     
  13. Hero999

    Hero999 Banned

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    I'm glad it works for you.

    As you're using a centre tapped transformer why not make full use of it and try building a bipolar power supply which can be used to power things like op-amps.

    Check out the bipolar power supply I made for ideas. Note, please read the whole thread in detail before you start anything because it still needs a bit of tweakking. Also note that you won't be able to get +/-15V from your transformer, you'll be able to manage +/-12V on light loads and +/-10V at full load.
     
  14. Peter_wadley

    Peter_wadley New Member

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    Currently I have been using my modified computer PSU for bipolar circuits. Since I only have -12v, which is rated at only .3A, I will be looking into a more powerful bipolar supply.

    Thanks for the suggestion and I will check out your thread now.
     
  15. Peter_wadley

    Peter_wadley New Member

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    Enclosure Assembly

    I’ve finally got around to assembling the enclosure..

    Note: changed LED resistor to 1000k for a better green coloring.

    PIC# 1
    Here is the aluminum box I bought.

    PIC# 2
    Here is the box after I have drilled all the holes and painted it gloss black. (2 Coats)

    PIC# 3
    Top view

    PIC# 4
    Bottom half is on the left.. It contains the transformer and PCB.

    Top half is on the right.. as you can see 4 screws attach the fan, the red button will be used to turn the fan on and off.. will talk about the reasoning later..

    You can also see the SPST on/off toggle switched used to cut the mains when the PS is not in use.

    A small grommet is also seen which will house the green LED.

    PIC# 5
    Coaxial DC jacks mounted and wired up..

    PIC# 6
    Better View..

    PIC# 7
    In this blurry picture you can see how I have kept the PCB tracks from shorting out on the aluminum box.. (2 nuts used to raise the board)

    PIC# 8
    One Main wire connected to the SPST

    PIC# 9
    Other main is connected to transformer.. shrink wrap is used to insulate the solder points

    Before I get a back lash of hate messages.. I will be replacing the white extension cord with a grounded cord for safety..

    Sorry, I couldn’t wait any longer to play guitar!

    PIC# 10
    The perforated holes in the back is to supply air flow for the fan.

    PIC# 11
    Bye bye wires.


    PIC# 12
    Rubber feet.. to stop sliding and raise the transformer and PCB screw heads off the ground.

    PIC# 13
    Rubber feet ON!

    PIC# 14
    The finished back.. again the cord will be changed.

    PIC# 15
    The finished front.

    PIC# 16
    PS powering a guitar pedal..
    - LED working, check
    - Fan working, check
    - Fan toggle switch working, check
    - mains switch working, check
    - House does not blow up on power up, check :p

    PIC# 17
    By the way, for those wondering, this guitar pedal was my first electronic project... as for the name, what can I say.. Arnold is the man.

    PIC# 18
    It is an octave ringer.. sounds great.

    PIC# 19
    Power supply powering the three pedals:

    - My pedal
    - Boss metal zone
    - and CryBaby wah..

    Black paint turned out very sharp :)

    PIC# 20
    Paint matches my AXE

    You can always add labels if your feeling saucy... the dollar store usually has blank white sticker paper which bonds to metal very well.

    Things I learned making this project:

    - Don’t give your father the chance to say 'I told you so' by spray painting in the laundry room - big mess :eek:

    - For that matter don’t use spray paint at all.. I recommend liquid rust paint.

    - Experiment with different LED resistor values until you find one which gives a good color.. Originally I had used 330:eek:hm: for the green LED .. This made it an ugly yellow color

    The reason for adding the fan was to elminate the heatsink..

    &

    The reason for adding the fan on/off switch is because when my homemade guitar pedal, which does not have adequate filtering, is turned on you can slightly hear the oscillating of the fan.

    That’s all folks,
    Peter Wadley
     

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  16. gramo

    gramo New Member

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    Looks good!
     
  17. Peter_wadley

    Peter_wadley New Member

    Joined:
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    Total Cost for me: (CDN Funds)

    -Enclosure: $10.00
    -12v Fan: $7.00
    -Transformer: $12.00
    -2x SPST switches: $7.00
    -2x grommets: $1.00
    -3x DC coaxial jacks: $2.50 x 3: $7.50
    -3 Pairs of DC plugs: $3.00
    -Copper Board: $4.00
    -Gloss Black Paint $4.00
    -Nuts and screws: $1.00
    -Rubber Feet: $1.00

    Components:
    Resistors, Capacitors, diodes and LED: $5.00
    LM317: $1.50
    Bridge Rectifier: $2.50
    Fuse w/ holder (not needed): $3.00

    Total CDN: $69.50 :eek:
    Total USD: $60.00


    Originality comes at a hefty price.. Definately not economical.. but im sure if you look harder you will be able to find things alot cheaper..
     
  18. Zed

    Zed New Member

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    OK. The fan is deffo not needed for this project.
    In fact you could put a series regulator powering 3 guitar effect pedals in a domestic oven at 50 degrees centigrade and it will still power 3 pedals.
    A wall wart psu for 10 pedals and possibly more can be easily constructed.
    If you go down the SMPSU route you can get several amps of DC at 10 volts EASY.
     
  19. Peter_wadley

    Peter_wadley New Member

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    Yeah, I suppose the fan is a bit overkill.. o well it looks cool and I enjoy a nice gently breeze on my face when Im playing.

    Also it acts as a hand dryer.. much the same as those found on bowling turnstiles.

    This power supply could manage 10 pedals.. if I mounted 7 more coaxial jacks.

    Thanks for the feedback
    Peter Wadley
     
  20. Ambient

    Ambient New Member

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    The reason why the lm317 is getting so hot is that it has to dissipate the extra Watts. The regulator is reducing the output voltage to 9V, but if you have a 25V transformer it has to dissipate all the extra voltage and current. So it generates heat.

    Just thought I'd clear that up for you, I did not notice anyone tell you why to go with a lower voltage transformer.
     
  21. Zed

    Zed New Member

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    I was just thinking that an even better idea would be to use a fixed 9 volt regulator like a TS7809CZ as well as a lower secondary voltage transformer.
    You could ditch the fan which will prolly induce electrical noise into the DC output anyhow.
    It would reduce the component count and the cost too.

    http://www.maplin.co.uk/module.aspx?ITAG=SPEC&ModuleNo=46475&doy=9m4#spec
     
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