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  1. HellasTechn

    Advice about MC34063 based buck converter diagram

    It looks like that i am not able to measure the ripple with the Oscope. I have builded the circuit on a PCB and things are alot different now. I will show pictures.
  2. HellasTechn

    The simplest definition of VOLTAGE you can come up with

    Maybe this picture will help you a bit to "get the picture".
  3. HellasTechn

    Help select suitable Mosfet for driving relay.

    I agree. I do have a Tektronix 3012B at work but i can not afford to buy one, i have a wife and two kids :) I had no time to investigate what happened with the BC337. I replaced them with the IRL520 and works fine so far. I am focused on the Power supply i wanted to make. By the way i wanted...
  4. HellasTechn

    Help select suitable Mosfet for driving relay.

    I do not have one at the moment but i will. Thats right. I also use a pull down resistor on the irl520 in order to keep it open during boot period of the arduino. Other than that i do not think it is needed for logic level mosfets.
  5. HellasTechn

    Help select suitable Mosfet for driving relay.

    so does this resistor have to be close to the relay or it does not matter ? . What would be the best resistor value for that ? 120Ohm like suggested by Bluejets ?
  6. HellasTechn

    Help select suitable Mosfet for driving relay.

    Should i add a gate resistor to make sure that no current will go back to the microcontroller in case the mosfet fails ?
  7. HellasTechn

    Advice about MC34063 based buck converter diagram

    I should probably make a new thread about this question but anyway. I see that the buck converter is noisy no matter what so im thinking that since my project is of big importance and i need tie microcontroller to be as reliable as possible. i could try feeding the 12V to an 7809 Vreg which in...
  8. HellasTechn

    Advice about MC34063 based buck converter diagram

    I wonder how the capacitor i placed between pin 1 and pin 2 affects the circuit and reduces ripple. I saw it in a car USB charger that i have...
  9. HellasTechn

    Advice about MC34063 based buck converter diagram

    i think it is 40Khz. since Vin=12V Vout=5V and Ct=470pF. The problem is that i do not have good quality low ESR capacitors...
  10. HellasTechn

    Advice about MC34063 based buck converter diagram

    Okay. i used the diagram as in the datasheet with slight modifications as shown below and i got it working. now i will try adding the optional output filter to see what happens.
  11. HellasTechn

    Advice about MC34063 based buck converter diagram

    Adding a 100nf ceramic capacitor between pin 1 and pin 2 seems to help alot but still after adding load (the actual arduino board with an LCD) things get really ugly. all pictures are with the load attached. picture 0 shows the output with a 220uf output capacitor. picture 1 shows the output...
  12. HellasTechn

    Advice about MC34063 based buck converter diagram

    Yes i can get pictures. It looks ripply to me. At the moment i am going through my connections again to make sure that i have everything okay on the breadboard. I do suspect the breadboard itself causing this though.
  13. HellasTechn

    Advice about MC34063 based buck converter diagram

    I received the 34063 today and started experimenting on the breadboard. I used the values recommended by the design tool. I gave it the following parameters: Vin=12V Vout=5V Iout=500ma Vripple=60mv So it gave me the following values: Ct=947 pF Ipk=1000 mA Rsc=0.3 Ohm Lmin=142 uH Co=104 uF R1=1k...
  14. HellasTechn

    Help select suitable Mosfet for driving relay.

    I understand your thinking but no. not really. Unless there is something i am not aware of like a pcb defect. Again dont think so since all readings are good. Come to think about it i can buy a few BC337's from my local electronics shop and run them for a few days to see what happens. I know...
  15. HellasTechn

    Help select suitable Mosfet for driving relay.

    Actually i was too lazy to look for the DPDT symbol in the drawing software :p Again like you said it the same thing, only in my case i want to drive two DPDT's with the same MOSFET from one arduino output. The cause is probably ebay-china... What else could it be huh ?
  16. HellasTechn

    Help select suitable Mosfet for driving relay.

    OOOPS, my bad !!! It is VCE = 11.97V that was a typographical error. SORRY.
  17. HellasTechn

    Help select suitable Mosfet for driving relay.

    I have one other question. if i use the mosfet to drive the relay then i suppose i can add one more relay in parallel. there should be no problem right ? Like in the attached diagram.
  18. HellasTechn

    Help select suitable Mosfet for driving relay.

    Ok, here are the readings. The supply voltage is 11.97V and the readings on the transistor (emitter to ground) with the relay engaged AND A 1K base resistor are as follows: VCE = 0.09V (positive terminal to collector) VBE = 0.75V (positive terminal to base) VBC = 0.66V (positive terminal to...
  19. HellasTechn

    Help select suitable Mosfet for driving relay.

    No. The transistors do not run hot at all. i will measure voltages and let you know.
  20. HellasTechn

    Dehumidifer - Does not Power On. Faulty Power Supply Board.

    The black 470uf capacitor also looks bad. I would just replace them all to be on the safe side.
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