Search results

  1. audioguru2

    6V Ultra-Bright Chaser

    I nearly got arrested for having a blue ultra-bright LED blinking on my dashboard. It was in summer but the law reserves blue flashing lights only for snow plows. He, he. ;D ;D
  2. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Maksar, Those torroid transformers probably have ferrite for cores, not iron, and they have very few turns in the coil. They look like high frequency switching transformers to me and cannot be used as mains transformers. I have never used 3.3V except for the 486/100 in my old computer. I...
  3. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Maksar, Thanks for the compliment. ;D Your English is fine. ;D Each meter will need a power supply that is completely separate from each other and separate from the power supply project. You can't connect a switching transformer to the mains without a complicated switching circuit driving...
  4. audioguru2

    Convert 12 VDC batteries to 8.4VDC

    Hi Even, It makes a big difference that your camcorder doesn't need a 7.5A power supply circuit. ;D An LM317 is rated between 1A and 1.5A so might not be enough. An LM350 is rated at 3A and will work fine. It will dissipate about 9W so will need a medium-size heatsink.
  5. audioguru2

    Speed-limit Alert PLEASE HELP!!!!!!!!

    Hi Pieter, I didn't check the design nor your pcb for the maze of parts around IC3B. Maybe it is normal for it to give a repeating 1 second pulse without an input due to the high gain front-end amplifying its own noise. Maybe with a strong input signal it will be fine. When you attach the...
  6. audioguru2

    Speed-limit Alert PLEASE HELP!!!!!!!!

    Hi Pieter, Yeah, pots work better when they are wired as pots. ;D I checked everything OK up to the 2nd half of the 4098. Does the 1st LED flicker OK with the sparks?
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Divljo, You have lots of dead parts. I don't know what happened to Q2, C3 and D7. I don't understand why the voltage at pin 4 of U3 and at D7 aren't the same. Good luck with rebuilding it or making it again. ;D
  8. audioguru2

    6V Ultra-Bright Chaser

    Hi Ante, I don't need one in my bathroom. They are bright enough to shine all the way across my livingroom, down the the hall and around the corner. They even shine under the closed door. I can make my whole neighbourhood glow when it is foggy at night. ;D
  9. audioguru2

    Speed-limit Alert PLEASE HELP!!!!!!!!

    Hi Pieter, Welcome to our forum. ;D I found our project here: http://www.electronics-lab.com/projects/automotive/004/index.html Did you sustitute any parts? Which opamp did you use? Please post your pcb layout and component mounting layout. The schematic is here:
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Divljo, Don't install Q1 without fixing your negative supply. The function of Q1 is to short the output of U2 to ground when the negative supply disappears when you turn-off the supply. You've been there and done that, with the power turned-on. Your LED DVM circuit must have strained and...
  11. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Divljo, There, you see? Your -5.6V supply doesn't work and therefore the U3 current regulator comparator doesn't work either because it needs the -5.6V supply. Check its 7 parts and replace U2 or U3 if they are hot. Your voltage across the 5.6V zener diode D8 is low because you probably used...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Divljo, I think your current regulator and Q1 should work with the 7805 and 7905 regulators and R23 and R24 removed. The fairly high DVM display current is overloading the negative 5.6V supply. You can power the DVM regulators with a separate transformer, rectifiers and filters. The current...
  13. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Divljo, Great! It works! ;D ;D ;D  ;D ;D ;D  ;D ;D ;D                ;D ;D ;D  ;D ;D ;D  ;D ;D ;D                ;D ;D ;D  ;D ;D ;D  ;D ;D ;D I think the voltage adjust pot has a mechanical short inside where its slider touches one end of its track at a certain position. Also it doesn't go...
  14. audioguru2

    boost converter

    A single turn of wire doesn't make much magnetism or pickup much in the core unless it is carrying many hundreds or thousands of amps, or unless it is used for low impedance, low level very high frequency circuits like the tiny balun transformer in a 75 ohm TV cable splitter box. Ferrite is good...
  15. audioguru2

    Convert 12 VDC batteries to 8.4VDC

    Hi Alun, 1) We don't know if the camcorder has enough filtering to be used with a switching supply. 2) This will take care of your comments:
  16. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Divljo, R14 is fine as 1.5k with your transformer. Maybe the 7805 and 7905 regulators were shorting the negative supply. ??? Maybe one of the negative supply's parts failed. ??? Maybe D5, D6 or D7 is mounted backwards. ??? Without a negative supply, U2's output will go as high as it can, but...
  17. audioguru2

    Convert 12 VDC batteries to 8.4VDC

    Hi Alun, The MJ3055 has a max leakage current of only 0.7mA with 30V across it, lower leakage with this application and the LM317 has plenty of output current through the 120 ohm resistor and pot. Why does the circuit need more minimum load current? ??? Hi Ante, I don't think the video and...
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Thomas, R23 and R24 are added to make what looks like a psuedo 0V for the 7805 and 7905 regulators. Then maybe the 7805 will have an input voltage within its 35V absolute max rating and the 7905 will have an input voltage higher than -7V or -8V so that it doesn't drop-out. I think that R23...
  19. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Divljo, Welcome to our forum. ;D I think your U2 gets very hot and its output measures 0V because either the pcb is shorting its output to 0V, or the TL081 has failed because the total of 35.7V positive supply plus the 5.6V negative supply (when it first worked) far exceeded its absolute max...
  20. audioguru2

    Convert 12 VDC batteries to 8.4VDC

    Hi Even, Are you sure that your camcorder has a powerful bright light so draws 7.5A? I thought that you wanted 8.4V for it. Your circuit with a 2N3055 emitter-follower boosting the current of a 7808 will have an output voltage of only about 6V, because the base-emitter voltage of a 2N3055 could...
Top