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5V Buck Regulator — Parallax Forums

5V Buck Regulator

SailerManSailerMan Posts: 337
edited 2009-01-23 18:53 in General Discussion
My robot is going to have a main 12v source, not uncommon I'm sure. [noparse]:)[/noparse] I currently use 7805 regulators to achieve 5V, I've been researching 5V buck DC-DC regulators and was wondering if anyone else has had success driving SX's and propellers from these types of regulators. Is the power savings that much better than a linear Regulator? Can I build these right on the PCB that the Micro is on or does it have to be better Isolated.

What ICs are you using to convert from 12V to 5V?

Any experience and advice would be welcome.

Regards,
Eric

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2007-10-09 16:34
    You can get pre-made buck regulator modules with a 7805 pinout from DigiKey. A typical part number would be PT78ST105V. They also carry the National "Simple Switcher" line of control ICs. The LM2594 is an example. With just a few external components, you can build your own buck regulator.

    -Phil
  • SailerManSailerMan Posts: 337
    edited 2007-10-09 16:49
    Have you ever built and used one?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2007-10-09 18:05
    Not yet. I'm planning to, though. I've used the TI 7805-like modules, though, and they work fine. But they're much too pricy to design into a product.

    -Phil
  • Sparks-R-FunSparks-R-Fun Posts: 388
    edited 2007-10-12 04:42
    Eric,

    You may want to check out Astrodyne’s product line. I have used their part #DU1P0-24S05 to power SX based devices from a 24V industrial supply that was already in the enclosure where the SX was being mounted. They have worked very well for me. The equivalent part number for you would be DU1P0-12S05 to convert 12V to 5V. These are 1 watt UNREGULATED converters. My application did not require regulated power, just something within the operating range for the SX and some attached peripheral chips. You might want to purchase a regulated converter or perhaps one with a higher power rating.

    Having said that, if someone is going to design or locate a more inexpensive 12V to 5V DC converter I would like to participate or at least hear what you uncover. I do not claim that the Astrodyne parts are the best or the cheapest, only that they have worked well for me in a few applications where my main concern was dropping the voltage while reducing heat buildup.

    - Sparks
  • SailerManSailerMan Posts: 337
    edited 2007-10-25 00:38
    Here is the First incarnation of·The 5V / 3.3 Volt Buck Regulator... So Far So Good.. Thanks for the Tips. It's basically a duplicate of the Data Sheet. [noparse]:)[/noparse] With a few additions.

    I'm using LM2595 Switching Regulators. One Side is 3.3 Volts and The other is 5V Both from·a 12V Input.

    Sorry about the crappy photo, I still have not managed to take good PCB Photos. I made this with 90% SMD parts.




    Post Edited (SailerMan) : 10/25/2007 12:54:23 AM GMT
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    Image 2.jpg
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  • DgswanerDgswaner Posts: 795
    edited 2007-10-25 01:35
    sweet! this is exactly what I was needing for one of my projects... any chance of getting a through hole version? I still haven't dared to do surface mount PCB's yet. or a schematic at least.

    about taking pictures of PCB's try stand back about 3 ft' +/- then zoom in. doesn't always work but usually better than trying to do a close up shot.

    Nice Project!

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    A complex design is the sign of an inferior designer. - Jamie Hyneman, Myth Buster
  • SailerManSailerMan Posts: 337
    edited 2007-10-25 02:25
    I can upload a schematic, Will that help? I'm not sure what you mean by , "any chance of getting a through hole version" Are you looking to buy one or make one?

    Thanks for your positive comments. [noparse]:)[/noparse]
  • DgswanerDgswaner Posts: 795
    edited 2007-10-25 16:12
    I need to get a 3.3 and 5 volt power supply of some kind, so I need to make one or buy one, are you selling them? if your selling them I of course don't care if it's surface mount to through hole. If I make one I would need to make a through hole PCB. A schematic would be helpful.

    Thanks

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    A complex design is the sign of an inferior designer. - Jamie Hyneman, Myth Buster
  • SailerManSailerMan Posts: 337
    edited 2007-10-25 17:17
    Oh.. ok.. Well let me play around with it a while and make sure it performs up to expectations and I'll PM you to see if you want to buy it, cool? Just parts and shipping.

    I know this unit runs perfectly from a 12 volt power supply, but I am not sure if it runs from a 12 volt battery.. If you only need this for a BenchTop unit this small unit already performs well.

    I'll Post the schematic when I get home later.

    OK it's later so I'm uploading a quick snap shot of the Basic Layout that I'm Using.



    Post Edited (SailerMan) : 10/25/2007 11:25:24 PM GMT
    Buck Schematic.jpg
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  • Paul HopkinsPaul Hopkins Posts: 1
    edited 2007-10-29 02:47
    I've used the switching regulators from Dimension Engineering (http://www.dimensionengineering.com). They're about the same size as the 7805.
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2007-11-28 23:03
    SailerMan

    Do you have any of these boards and parts for sale

    Can you Please let me the cost of them you can PM

    Thank you for your time in this matter

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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
  • SailerManSailerMan Posts: 337
    edited 2007-11-28 23:33
    Sam,

    I have not concidered selling these yet, I was trying it make it better and smaller. When that happens I can certainly let you know.

    Eric
  • Steve JoblinSteve Joblin Posts: 784
    edited 2007-11-29 01:04
    I'm thinking about incorporating an XBee in my next robot, so I will need both 5v and 3.3v supplies... this my be a perfect solution! SailorMan - If you could let me know price as well, that would be great!

    Steve
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2007-11-29 01:14
    SailerMan

    Thank You Eric

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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
  • SailerManSailerMan Posts: 337
    edited 2007-11-29 02:06
    I have got the board upgraded and sent to Batch PCB for a inexpensive proto-type.

    It has the ability to monitor the input voltage of the battery and give visual feedback as well as a serial data stream. I know it's overkill but lots of fun.

    I will build a basic twin power supply but I will need time to get this together as I wasn't planning on selling anything.. I will work up a price for the basic unit and let you both know. (Can you solder SMD ?)

    Remember it is designed for 12V input. I have not tried a 9 volt input... But I will find out if it will function that way.



    Here is a photo

    Post Edited (SailerMan) : 11/29/2007 1:17:50 PM GMT
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  • Steve JoblinSteve Joblin Posts: 784
    edited 2007-11-29 13:52
    I haven't soldered SMD's yet, but there is always a first time for everything... I would like to know if it works with a 7.2V supply before I buy though... (my robots tend to be small)
  • pwillardpwillard Posts: 321
    edited 2007-11-29 20:13
    I've had really good luck with a soldering iron and SMD's. A while back I posted my results of laser toner process with a ssop ( you can get an SX in this format in the SX proto board).

    Based in my very limited experience... SMD's are not worthy of generating so much fear. They are actually easier than imagined... but as I said in the past... using a good "F L U X" was the key to my success.· In my case I used a highly active water soluable flux for very fast wetting action which resulted in a· quick two step soldering process (once across the lands on the board and then a quick reflow by passing the iron across the part and the copper lands).· This may not alsways work... but the flux I used acted so fast I had zero solder bridges.· Something ROSIN flux would never accomplish.


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    There's nothing like a new idea and a warm soldering iron.

    Post Edited (pwillard) : 11/29/2007 8:20:58 PM GMT
  • Steve JoblinSteve Joblin Posts: 784
    edited 2007-11-29 20:17
    pwillard... can you direct me to the posting you made about the results of your laser toner process... I'm just starting to get into making my own boards... I purchased a laserjet printer, but haven't tried it out yet.
  • pwillardpwillard Posts: 321
    edited 2007-11-29 20:24
    Sure.· http://forums.parallax.com/showthread.php?p=667416

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

    There's nothing like a new idea and a warm soldering iron.
  • DgswanerDgswaner Posts: 795
    edited 2007-11-29 20:43
    Steve, the switching regulators are rated for 4.75v-40V on the input. so you should be covered. If your talking about 7.5 on the output it will not work. you'll have to switch to the Adjustable voltage version which isn't a drop in replacement for the preset regulators.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

    DGSwaner
  • SailerManSailerMan Posts: 337
    edited 2009-01-23 18:53
    A long time later and I've decided to resurrect this project. I never did get the board made but I'm thinking maybe I should... Has anyone else created a dual switching power supply?

    I've been using my prototype above for about 1.5 years and it is still going strong.. I've been away from electronics for almost a year of that time so I have to catch back up. It's amazing how alien a project can seem after only a short time.
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