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  1. KrisBlueNZ

    Laptop Backlight problem, Inverter works

    Hi and welcome to Electronics Point :-) The ADJ signal is probably just a variable DC voltage that sets the brightness of the backlight. Instead of making a circuit to feed a voltage into the ADJ input, how about measuring the ADJ and ON voltages on your machine and your friend's machine. Is it...
  2. KrisBlueNZ

    AVR ISP Simple Programmer

    That adapter will only work with a "real" parallel port - not a USB parallel adapter. The parallel port may need to be configured as "SPP" ("standard parallel port") in the BIOS Setup of the computer. What type of computer are you using? What operating system are you running on it?
  3. KrisBlueNZ

    (Electro)Magnetic Levitation

    LOL :-) Where did you connect the resistor? In series with the power input to the Hall sensor? What will drop a lot of voltage and prevent the sensor from working properly. As long as it's connected correctly, and is not damaged, it will not get hot. According to the data sheet, it draws a...
  4. KrisBlueNZ

    Component questions (transistor, capacitor)

    Right. That's a good idea, because for any given current limiting resistor value, the LED current depends on the voltage across the current limiting resistor, and this depends on how much of the supply voltage is left after you subtract the LED's forward voltage (and the collector-emitter...
  5. KrisBlueNZ

    Car audio problems: MP3 player into CD changer socket

    Bummer. Yeah, it's a lesson that many have learned.
  6. KrisBlueNZ

    Component questions (transistor, capacitor)

    At that current, you would probably be OK to drive them directly from the device's pins. But the buffer approach is tidier. Right. That's it exactly. Your schematic is right too, except you haven't added the base-emitter resistors. But of course you could replace each BC547 and pair of...
  7. KrisBlueNZ

    (Electro)Magnetic Levitation

    Pin 2 should be at about 2.5V if the trimpot is set at mid-position. If there is 0V on pin 3 of the LM348, there is definitely a problem. Double-check the connections to the Hall sensor. Holding the device so you're looking at the part number marking on the smaller side, and the leads pointing...
  8. KrisBlueNZ

    Component questions (transistor, capacitor)

    (MOSFETs) I guess you could say that. MOSFETs are three-terminal devices, like BJTs (bipolar junction transistors, aka "transistors"). Like transistors, they have a "control" pin that controls the current flow between the other two pins, but unlike transistors, they respond to the VOLTAGE...
  9. KrisBlueNZ

    12V Battery Charger Schematic

    It's R6. Efficient? Right, it will only save a few watts. If you want to leave the thing plugged in all the time, you might find it worthwhile to put a relay contact in series with the AC mains supply to the power supply that powers the charger circuit. Put a "START" pushbutton across the...
  10. KrisBlueNZ

    (Electro)Magnetic Levitation

    So pin 3 has 0V on it? This is the voltage from the Hall sensor. It should be +2.5V when the Hall sensor has no magnetic field applied, and it moves upwards or downwards (according to the direction of the field) by an amount proportional to the strength of the field. It should never be 0V...
  11. KrisBlueNZ

    Panasonic SA-200HE receiver not turning on

    Hi bookel and welcome to the Electronics Point forums :-) Yeah, sure! That sounds like a worthwhile repair. And you've given all the important information in your initial question, and used a good thread title. This gets you high marks in my opinion. And you have a multimeter. Good! I...
  12. KrisBlueNZ

    (Electro)Magnetic Levitation

    I guess you forgot to mention that you're using an LM348 instead of the 741 that's specified on the schematic. In that case, yes it's those pins you listed. Re the physical diagram, sorry, I didn't need to see the circuit board, only the electromagnet, the Hall sensor, and the location of the...
  13. KrisBlueNZ

    Driving an SSR input from a DC power adapter

    Yes, the power supply does have a capacitor. As BobK says, you can switch the output - i.e. connect an SSR or relay contact between the 24V DC output of the power supply and the 0.5A solenoid valve, but not that SSR - it's only designed to switch AC. You can get SSRs that are rated for DC. And...
  14. KrisBlueNZ

    Emergency Power Supply Schematic Diagram

    I think we are going to give up on the designs in this thread and continue on the other, related thread. I have replied to post #18 in the other thread: https://www.electronicspoint.com/12v-battery-charger-schematic-t267632.html#post1601944
  15. KrisBlueNZ

    12V Battery Charger Schematic

    This message is in reply to guitarnoob123's post on a related thread: https://www.electronicspoint.com/emergency-power-supply-schematic-diagram-t267497.html#post1601931 I think we are going to abandon the designs in that thread and continue with this thread. OK but how do you determine when a...
  16. KrisBlueNZ

    do you know these resistors?

    Of course Bob. I'm sure we can contain our excitement until the 20th :-) Yes, I would assume D3 is also a 1N4006. It doesn't matter if Circuit Wizard doesn't know about the BCxxxL versions, does it? As long as you know what the pinouts of the actual transistors are, so you can draw them...
  17. KrisBlueNZ

    Variable DC supply circuit - any critiques?

    I don't think that latest circuit will work either. The triac circuit needs AC across it to work, and the diode will block current flow during the negative half-cycles. Actually I'm not sure that the phase control method in conjunction with a smoothing capacitor is workable, no matter how you...
  18. KrisBlueNZ

    Emergency Power Supply Schematic Diagram

    Yes, I think you can abandon this design and go with something like the circuit in the other thread. As I said over in that thread, that circuit will over-charge the battery because its maximum output voltage is too high - 16.3V. But changing the resistor values as I described will fix that...
  19. KrisBlueNZ

    12V Battery Charger Schematic

    AFAIK you can omit it. Leave it open. Right.
  20. KrisBlueNZ

    Component questions (transistor, capacitor)

    (transistors with base resistors built-in) Cool! So you will be using SMT versions? There are LOTS of options. Yes. You should also consider using MOSFETs. MOSFETs are voltage-driven and don't require any drive current (except for a short burst when the control signal changes, to charge and...
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