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RubicK

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About RubicK

  • Birthday 11/30/1987

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  1. Hi again! I have a problem with supply for my digital meters connected to this PSU. I have made a supply circuit for this meters. There is a diode bridge, capacitors (2x 100n + 100uF) and 78L09 stabilizator. This circuit is connected to output pins on transformer, where is 24V AC. Voltage on output of circuit is exactly 9V, but when i connect it to meters, they show absurd values and the numbers are blinking. But when I connect them to a 9V battery, everything is OK. In the meters manual there is NOT written that supply voltage must be absolutely indepedent on voltage being measured. Is there any way how to modify this circuit to make digital meters work? Thanks
  2. Hi audioguru, I tryed it with DC motor and 100n across inputs of voltmeter - when motor is rotating slowly everything is well, but when rotations raise, voltmeter shows absurd numbers (It is a 3V DC motor. Bellow 2V everything is well but then voltmeter starts to show that voltage is about 8V and it is still changing beetween 2 and 8 volts. i measured it with multimeter and it showed 2.7V, so in that multimeter must be some shielding.). This happens only with motor, when i connect another aplience like bulb or radio receiver, everythung is OK. Do you thing that it will help to add one more 100n capacitor accross input of voltmeter? thanks
  3. Thanks for you fast answer, audioguru. I have one more problem with my digital voltmeter. I think it is very sensitive. The range is 200mV and it is increased to 200V by a voltage divider. Sometimes it shows various numbers. For example when i touch with an unconected piece of wire on one output pin the display will show absurd values for a second and then will return to normal value, but somethimes it stay confused displaying absurd values or displaying a zero value still. But when i touch with my finger somewhere on the meter's PCB, it returns to "normal mode". I used exactly same voltmeter as an ammeter, but i didn't noticed this problem there. Can it be caused of using a transformator soldering gun? thanks Modified on 30th December 6:35 AM I have also tryed to connect a DC motor, but when it starts to rotate, various numbers blink on both voltmeter and ammeter. I have tryed to add a 100n capacitor paraller to output pins. It is better, but when nuber of rotations increases it starts to do it again. Is there any way to supress disturbing? thanks
  4. Sorry, i have made a mistake :-//. This is not valid. Led doesnt light when no load is connected (so thats good).
  5. Hi all. I have just made this PSU. Everything works fine, but the current pot is regulating from about 0,02A to about 4,4A, but i want only 3A. Also when no load is connected and current pot is set to minimal current LED lights. I have some modifications on it. There are 2 paraller 2N3055 (0,33ohm resistor on each emmiter), increased power of resistors and digital meters. Ampermeter is coonected to the negative output of PCB. Can you help me? thanks
  6. I cannot download that image, it always downloads a 0 byte file.
  7. I founded next 2 errors: R2 must be 82Ohms instead of 82k, and R17 must be 33Ohm instead of 33k!!! I hope that this errors couldn't damage any part on PCB...
  8. Oh thats unbelievable! I have been bulding this supply according translated article: http://www.hw.cz/Teorie-a-praxe/Konstrukce/ART1438-Napajeci-zdroj-0-30V-s-regulovatelnym-proudem-2mA--3A.html Author of this text made a mistake in part list, he wrote that R3 is 220kOhm instead of 220 Ohm, could this be that mistake? i measured voltage in front of R3 and it was about 6,1V then i measured it behind and it was about 0,6V
  9. I have checked parts you have written, but i have nothing found. I am a beginner in electronics, so it is hard form me to find a mistake. I tryed to disconnect Q1 from the PCB. Voltage on output was about 30V but i couldn't regulate it. Can you also tell me what parts makes that 5,6V negative Voltage? Thanks
  10. Hello, i have made this power supply and it doesn't work. When i turn it on, U2 is heating very much, current is around 100mA, potensiometers doesn't do anything, voltage on output is abou 0,2V. I have checked PCB and connection of each part, but i didn't found a mistake, please help i realy don't know what to do. Thank you, RubicK, Czech Republic
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