How to choose the right connecting wires?

Discussion in 'General Electronics Chat' started by Devika B S, Mar 14, 2017.

  1. Devika B S

    Thread Starter Member

    Mar 8, 2017
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    I made a boost converter yesterday night and it worked fine with a 9V 500 mAh battery. However as soon as I connected my 12V 1.2 Ah battery, I smelled something burn at the positive terminal of the battery connected to the breadboard. I disconnected it immediately. To my utter disgust the converter is acting as a buck converter now! :confused: I checked the batteries and resistors, they are undamaged. Tomorrow I will check the switch, diode, inductors and capacitors. But I think that the wires are damaged. It began to develop I2R heat and burn. Can anyone suggest a solution? What wires should I use to withstand upto 2A? Can the breadboard withstand this? Plus, the online electronics store where i order stuff doesn't have any spec for wires. It just says connecting wires. Also when does a boost converter act like a buck converter? (Earlier with 9V, I got 18V output. 12 V battery- burns- immediately disconnected. Again connected the 9V battery getting just getting1.5V output :(). All batteries remain undamaged.
     
  2. AlbertHall

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    Jun 4, 2014
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    Schematic please.
    What is the voltage rating of the capacitors?
    Any 'normal' plastic insulated wire you buy will cope with 2A comfortably. The wire isn't the problem. What sort of breadboard is it? The kid with solderless plug-in connections are not really intended for power circuits.
     
  3. Devika B S

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    Mar 8, 2017
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    Yes its an ordinary breadboard with solder less plug in connections. Capacitor is rated 33 uF, 60V. The schematic is that of a normal (1 stage) Superlift Luo Converter. How much current can this bread board withstand? What should I do to implement this circuit? The my circuit draws 1.05A from the battery. Since its a boost converter, output is low - just 0.23A (But output voltage is 48 volts).
     
  4. AlbertHall

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    As I understand this is the basic circuit of this converter:
    upload_2017-3-14_12-16-20.png
    If this is what you are using, then if you are getting 1.5V output with 9V input it follows that one or both diodes are open circuit.
    Please post the actual schematic you are using.
     
  5. Devika B S

    Thread Starter Member

    Mar 8, 2017
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    I have attached the circuit diagram (It is a screen shot from digikey). An input LC filter is used to reduce inout current ripple. Else the circuit is same as you sent. I have also a screenshot of the circuit as simulated in MATLAB. Tf.png Simd.png
     
  6. Devika B S

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    Mar 8, 2017
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    You mean that the diodes are damaged (when burning occurred)? But when I remove the gate pulse from MOSFET (a logic level MOSFET triggered by Arduino with 150 kHz frequency, 67% duty cycle), I still get 9V output. When the gate pulse is there, I get 1.5V output. That's why I said it is behaving like a buck converter.
     
  7. AlbertHall

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    To understand what is going on I need to see the schematic.
    [Edit] Just seen you have posted a schematic. I'll get back shortly.
     
  8. Devika B S

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    Mar 8, 2017
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    This is the schematic Schematic diagram .png
     
  9. AlbertHall

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    Can you give values for the inductors and capacitors please.
     
  10. Devika B S

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    Mar 8, 2017
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    Lin = 25 uH
    Cin = 10 uF, 16V
    Above two are for filter
    L1 = 100 uH (hardware is the inductors that look like resistor meaning not a choke or coil)
    C1,C2 = 33 uF, 60V
    R =1300 ohms (But multimeter reads 1700 ohms when connected)
     
  11. AlbertHall

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  12. Devika B S

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    Mar 8, 2017
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    Yes. Its the same inductor. But the online shopping website did not have the current ratings :(. Now, will a choke inductor have 1A current rating?
    Choke inductor.png
    Will this do? It has a current rating of 1.4A and I am planning to connect two inductors in series so as get 94uH which is close to 100. (This is the only inductor available in online stores with a current rating, 100uH not available)
     
    Last edited: Mar 14, 2017
  13. AlbertHall

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  14. AlbertHall

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    But as it used to work and now doesn't something has changed/broken.
    The inductor and C1 are prime suspects.
    Do you have an oscilloscope?
    DMMs are generally not much use at 150kHz.
     
  15. Devika B S

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    Mar 8, 2017
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  16. AlbertHall

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    It's a bit weird but I don't see why it shouldn't work.
     
  17. Devika B S

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    Mar 8, 2017
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    I don't have an oscilloscope at home right now. But I can use one at college tomorrow. So you mean to say that the choke inductors are not very useful at 100 KHz ? (Sorry its 100 kHz, not 150 as I mentioned before)
     
  18. AlbertHall

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    The inductors should be fine. The difficulty is getting useful diagnostic measurements at 100kHz without a 'scope.
    Connect the scope to the three diode connections and the MOSFET drain. Record the maximum and minimum voltages of the waveform at each of those four points.
     
  19. Devika B S

    Thread Starter Member

    Mar 8, 2017
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    OK. I am purchasing five 22uH choke inductors immediately (the 27uH inductor just went out of stock a few seconds back. People are buying so much chokes I suppose). I will use a DSO at college research lab specifically meant for measuring very high frequency waveforms.
     
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