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  1. KrisBlueNZ

    Split Rail Power Supply

    Q5 must be at the same temperature as the heatsink with the output transistors on it. Since Q5 is in a TO-92 package, which is a cylinder with a flat on it, it's common to press the flat face against the heatsink, using some kind of spring clip. Alternatively you can drill a hole in the heatsink...
  2. KrisBlueNZ

    Voltage controlled thru opamp playing up?

    The MCP6004 looks suitable. You should tie the non-inverting inputs of the unused amplifiers to something. For example, VSS. The smallest sized text on that schematic is barely readable. Can you give component values. Can you give a link to the transducer/sensor. How have you built up the...
  3. KrisBlueNZ

    Tesla coil-Will this circuit work?

    You could start by Googling make a Tesla coil. I found quite a few hits.
  4. KrisBlueNZ

    LM7805CT Heating up

    Another really good answer kpatz! I'm glad we have you on board :-)
  5. KrisBlueNZ

    Split Rail Power Supply

    Yeah, it's easy to forget to put the little triangle in there, and every time I do, I get errors. I'm a bit surprised that it needs it really. I guess you could connect the triangle to any point in the circuit and the simulation should still work. Maybe connecting it to a reference point makes...
  6. KrisBlueNZ

    A Canadian says Hi

    Welcome to Electronics Point :-)
  7. KrisBlueNZ

    VOX DA5 Amplifier repair help - no power when plugged in

    OK. I would definitely recommend that you resolder the socket to the PCB. All you need is a soldering iron (called a "soddering iron" over there), and some solder (or if you can't find that, some sodder will do). For the iron, pretty much any cheapo piece of crap that's rated for 30~50 watts...
  8. KrisBlueNZ

    mV voltage reference for a comparator

    Comparator outputs can be clean, yes, but without hysteresis, a noisy input can cause multiple transitions on the output as it passes through the comparison voltage. A comparator with [a small amount of] positive feedback = a comparator with hysteresis = a Schmitt trigger.
  9. KrisBlueNZ

    Split Rail Power Supply

    Dave's answers are right except: It's needed by the simulation software. It tells the software that this is the "0V" rail, i.e. the rail that all voltages are (by default) measured relative to. It doesn't have to correspond to anything in reality. If I didn't have one there, when I tried to...
  10. KrisBlueNZ

    Voltage controlled thru opamp playing up?

    Hi Mike, and welcome to the Electronics Point forums :-) Can you start by uploading a schematic please. Edit: Also, can you give us a link to the data sheet for the sensor please.
  11. KrisBlueNZ

    Tesla coil-Will this circuit work?

    Hi Kari and welcome to the Electronics Point forums :-) What frequency is the oscillator supposed to be operating at? What type of transformers do you plan to use for each stage? Can you upload pictures of them? To attach images to your post, click Go Advanced and click the paper clip icon in...
  12. KrisBlueNZ

    Pic and JTAG Programmer

    The restaurant menu thing was supposed to be a joke!
  13. KrisBlueNZ

    Transistors heating up when sinking from motor

    Yeah, what Steve said. MOSFETs are the answer to this problem. Or you can get an H-bridge IC with everything inside it. But that's no fun eh! I think you should try to figure out the situation with the bag of 2N3904s that you have. If they're faulty, you should throw them out to avoid...
  14. KrisBlueNZ

    Hello, Welcome! (Introduce yourself)

    Hi Tom :-) Welcome to Electronics Point! I'm sure we can help with the amplifier. I see you posted a video of it! That's a great idea.
  15. KrisBlueNZ

    Pic and JTAG Programmer

    Great :-/ It's probably a menu from his favourite restaurant! Well, he should know that's no use to you. What you do is up to you, I guess. You could try demanding English documentation and threatening to post bad feedback - I think you would be justified in doing that. Or you could try to find...
  16. KrisBlueNZ

    Half Bridge Converter Question

    No, they don't "supply energy"; they block DC. They function just like a series capacitor. The voltage at the middle node will stabilise at roughly half the supply voltage, but that's not because the capacitors "create a half supply" voltage; it's because the duty cycle of the signal from the...
  17. KrisBlueNZ

    How do I build a Metal Detector?

    Yes Chris, we "crossed paths" :-) You raised an important point, and reminded me that the search coil needs to be stable as well as the capacitor.
  18. KrisBlueNZ

    How do I build a Metal Detector?

    Yes, the changes in frequency (or period) are small, short-term frequency variations. The microcontroller needs to establish the baseline frequency, which is presumably the frequency set by the inductor with no metal nearby, then detect and report increases and decreases in the oscillator...
  19. KrisBlueNZ

    How do I build a Metal Detector?

    No. An oscillator produces a continuous alternating signal. It doesn't use pulses generated by a microcontroller. An LC oscillator oscillates at the resonant frequency of the inductance and the capacitance. Well, the waveform across the tank circuit will be close to a sinewave, but you're only...
  20. KrisBlueNZ

    Half Bridge Converter Question

    The two capacitors across the power supply provide DC blocking to prevent flux walking. Huh? In both cases, both devices need to be rated for the full supply voltage, and in both cases, the peak-to-peak voltage seen by the primary is equal to the supply voltage. Connecting two capacitors in...
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