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DC/DC buck & boost converter

  1. Jul 9, 2017 #1
    Hello,

    I am trying to understand DC/DC converters because I want to use some with my solar panel system and I want to understand exactly how to use them in general. The videos I've looked up are confusing and I can't seem to find something to read that will help me understand.
    Is there some prerequisite knowledge anyone can point me in the direction of or an easy way of explaining it?
    I haven't memorized schematic symbols yet and I'm slowly getting into what different components do.

    Sorry if this topic is broad or vague. Thanks in advance
     
  2. jcsd
  3. Jul 9, 2017 #2

    jim mcnamara

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    Do you have any experience with PV installation? Youtube is not always the best choice when attempting to learn about something with a hazard potential.

    What exactly are you going to build? A small installation with a prebuilt kit? - in the US, Harbor Freight handles solar panels and premade kits, for very little cost.

    I would suggest you not try to go from scratch.
     
  4. Jul 9, 2017 #3
    I've built my own solar panel system and posted a thread.
    https://www.physicsforums.com/threads/diy-solar-power-system.918484/
    It's low voltage. I want to understand how to use DC/DC converters for the solar panels and eventually use these converters on small batteries to power peltier, fans, lights, actuators, etc.
     
  5. Jul 9, 2017 #4
    It is really a complete field of study. Have you reviewed the Wikipedia for Buck and Boost?

    But in a system - how they work is really not all that important. The next level - is how to control them, and then how to control a system using them... etc.

    If you could provide a more specific question, and are you just asking how to do something, vs how something works... that are quite different questions.
     
  6. Jul 9, 2017 #5
    I guess I don't necessarily need to know how they work, I just need to know enough to be able to buy and use them. Right now I don't feel comfortable enough to order them. I have checked Wikipedia and I'll look at it again and see if it helps. Thank you
     
  7. Jul 9, 2017 #6

    berkeman

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    It does seem like it would be good to get a little more up to speed on basic electronics, so you are comfortable working with the low-voltage circuits. What resources are you using to learn about basic circuits and components? A book like this one is a pretty good introduction to basic electronics -- if you can find a used copy somewhere, it may not be too expensive:

    https://www.amazon.com/Art-Electron...627406&sr=1-1&keywords=the+art+of+electronics
    51oDPY4SbfL._SX380_BO1,204,203,200_.jpg
     
  8. Jul 9, 2017 #7
    Looking at your previous post - you have a charge / inverter controller. -- the challenge may be that it probably uses a MMMT algorithm on the solar input - mixing different types of inputs may confuse it, and /or the output of the boost converters will not behave like a solar panel.

    There are solar boost converters for a few bucks, I would apply on to each panel, that way all of the outputs are the same type, but getting them to "share" the load may still be difficult - kind of like paralleling batteries of different types. But at < $10 each -- may be worth just trying it.

    IN general the circuits are the easy part - the controls will be more difficult.

    (As for the diodes - "axial" really is just a mechanical description - you may want to check what they are. Ideally they will be of Schottky type.)
     
  9. Jul 9, 2017 #8
    I've been reading:
    Uglys electrical references
    Make: Getting started with Arduino
    Make: Electronics
    Besides that I search on this forum, google, and YouTube (I watch multiple videos sometimes just to be sure)

    Thank you for telling me that, it's helpful to know!
     
  10. Jul 9, 2017 #9

    anorlunda

    Staff: Mentor

    A better question is why do you want a buck boost converter. If you already have a MPPT charge controller it optimizes voltages and currents. You should have followed the controller's manual instructions for how to connect multiple panels in series/parallel.

    Adding a buck boost converter won't create more power. In fact, there will always be losses in any circuit, so you will have less total power. It if did, then it would be built in to the charge controller.
     
  11. Jul 9, 2017 #10
    I knew there would be a loss in power when converting it, I wanted to use it to control amps and volts when powering different devices.
    Honestly it's to best option I could find to make a specific amount of volts and amps for an electronic device.
    For example, I ordered linear actuators from Amazon that operate on 12v and .8A - 3A (max) and I need to figure out how to lower the amps and volts to 12V 3A to operate it.
     
  12. Jul 9, 2017 #11
    Getting the voltage right for whatever devices you want to use is the main consideration.
    You don't need to worry about current, that's determined by the power requirements of your devices, your converter is either strong enough or it isn't.
    DC->DC converters work by turning the DC in to AC, then using a transformer to step the voltage up or down, and then reconverting that AC to back to DC.
     
    Last edited: Jul 9, 2017
  13. Jul 9, 2017 #12

    davenn

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  14. Jul 10, 2017 #13

    anorlunda

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    Oh no. You should study elementary circuit analysis. You're making things more difficult than necessary. As @rootone said, just find devices compatible with the voltage (like 12 v nominal which typically means anything from 10 to 14 volts) and the current takes care of itself. So to attach the 12v sensor to the 12v charge controller, you don't need a DC converter at all.

    The current rating of the converter (say 40 amps), is a maximum. The current draw of the sensor is typical. You need only make sure that the current draw of all loads combined do not exceed the maximum current from the controller.
     
  15. Jul 10, 2017 #14

    Merlin3189

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    There seems to be a lot of unnecessary talk about solar panels. It seems to me that you've got solar panels, you've got some control/management circuitry and probably some 12V batteries. Net result you have a 12V DC power supply and it doesn't matter where it came from.
    Your problem (or not a problem) is powering devices from a 12V DC supply. If you have or buy devices to operate from 12V DC, no problem. Otherwise you get a converter for the device so that it can operate on 12V. The device will decide the converter properties.
    If you are going to have several devices on one voltage, say 110V or 220V, then you might think about having an inverter create a general supply at that voltage, but it's probably simpler to have an adapter for each device.
     
  16. Jul 10, 2017 #15
    Thank you all, I don't know why but I couldn't find out if amperage would be an issue if it was too high.
    So if I got this correct, if I want to operate a DC device that's 12V 3A, I can connect it straight to a 12V car battery and it will just draw what it needs? Sounds too simple.
     
  17. Jul 10, 2017 #16
    It is that simple, the current drawn is determined by resistance of the device (in this scenario often referred to as 'load'
    Some devices will have a variable load, but will have a maximum rating which will not by exceeded if they are working properly
    So long as voltage is right it will draw whatever current it requires, however your supply must be strong enough to provide the required current.
    If isn't that will effectively cause the voltage to drop so the device won't work as designed.
     
    Last edited: Jul 10, 2017
  18. Jul 10, 2017 #17
    This makes things so much easier!
     
  19. Jul 21, 2017 #18
    Actually, a transformer is not needed for dc-dc converters. A simple inductor is used for buck, boost, & buck-boost networks. As long as isolation is not required, transformers are not needed.

    Claude
     
  20. Jul 21, 2017 #19

    davenn

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    thanks for the backup :smile:
     
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