Search results

Search Forums New Posts
  1. KrisBlueNZ

    linear mode 10A MOSFET current source

    OK, if you don't have a part number, at least tell us the specifications. Also, a photo of it, and any markings on it, would be very helpful. A "simple generic 10A current source" doesn't really exist. At that level of current, there are extra factors you need to consider in the design - heat...
  2. KrisBlueNZ

    need help with simple 3v to 34v transistor relay/switch

    You can calculate the bell current by measuring its resistance with your multimeter. Use Ohm's Law: I = V / R. So if you measure 100 ohms, for example, and you're going to be feeding 34V into it, V=34 and R=100 so I=0.34 amps. Make sure that your DC-DC converter is rated to supply that much...
  3. KrisBlueNZ

    Function Generator

    Ah, I wondered what that was all about. He probably chose not to use Number2 for obvious reasons... The toilet scene from one of the Austin Powers movies come to mind... "Number Two, who is your boss?" etc :-)
  4. KrisBlueNZ

    3D pov display Full Design

    Where are the schematics? I can help you with your spelling and punctuation if you want. I can't be bothered with a lot of mark-up but you can send me your source document, I'll fix the errors I can find and send it back to you, and you can do a document comparison to see what I've changed. PM...
  5. KrisBlueNZ

    Understanding NPN

    Hi Phil and welcome to electronics point :-) Yes, those three points do descend in voltage. (They are all the same polarity - positive with respect to the 0V rail, which is represented by the earth symbols.) R1 is a bit of a red herring. It's not needed as part of the circuit, and won't be...
  6. KrisBlueNZ

    4 Channel Diversity Controller

    Another question. Why do you want this function? Are the transmitters all on different frequencies so they suffer from fading under different circumstances? Or are the receivers at different locations? I can't think of any other reason why you would need four independent radio paths from the...
  7. KrisBlueNZ

    need help with simple 3v to 34v transistor relay/switch

    You may find that connecting the diode across the bell coil will interfere with the bell's operation. It may be better to use a transistor (or better, a MOSFET - but you'll need one with a low Vgs threshold voltage, unless you make a gate driver circuit that runs from a higher voltage) with a...
  8. KrisBlueNZ

    Building a battery-powered charger: feasible project for a beginner?

    As Steve says, the charge current (and therefore the charge time) is determined by the charger inside the device. You can't slow down the charging process by reducing the amount of current you provide; if you try to do that, the device will think the adapter is faulty, and will stop charging...
  9. KrisBlueNZ

    Alternatives to LDR for audio signal.

    To the OP. As I said, you will need four VCAs (voltage controlled amplifiers). Google up some schematics. I would recommend using operational transconductance amplifiers for these, as it's fairly simple. They would all be driven from the same signal source, and each one would drive a different...
  10. KrisBlueNZ

    linear mode 10A MOSFET current source

    Can you post the part number for the LED? And preferably a link to a data sheet for it?
  11. KrisBlueNZ

    Function Generator

    Has 'Number' changed his username, or has CluQu hijacked this thread without mentioning that he has just joined it?
  12. KrisBlueNZ

    Alternatives to LDR for audio signal.

    You need something that is (a) resistive, not a simple semiconductor, so it doesn't make a huge distorted mess of the audio signal, and (b) smoothly and continuously variable over a fairly wide range of resistance, so the attenuation can be smoothly controlled. Using an LED and a LDR, the LDR...
  13. KrisBlueNZ

    Modification of anti-bark control circuit - help please!

    Yes, I'd concluded that too.
  14. KrisBlueNZ

    Alternatives to LDR for audio signal.

    You can't use an optocoupler for variable audio attenuation.
  15. KrisBlueNZ

    rain warning device

    Good advice, eKretz.
  16. KrisBlueNZ

    Modification of anti-bark control circuit - help please!

    True, but even if the human-audible frequency is 12.5 kHz, say, and the dog signal is 25 kHz, that's only one octave difference; you will need a fairly steep filter - at least 12 dB per octave, perhaps twice that - if you want to reduce the human-audible signal significantly without affecting...
  17. KrisBlueNZ

    Modification of anti-bark control circuit - help please!

    OK. No, I don't think there's much point in tracing the signal with an oscilloscope. An oscilloscope would be useful, but first we need to know a lot more about the circuit. The pictures you posted are good, but I really need something better to work from. I need both sides shown looking...
  18. KrisBlueNZ

    Car Immobilizer

    Yes, lots of possible explanations. Weak battery, corrosion or dirt on the battery terminals or other contacts in the transmitter, dry joints in the transmitter or receiver... Pretty much any kind of intermittent problem. There's no need to be paranoid... unless they reallly ARE out to get you...
  19. KrisBlueNZ

    fet multimeter

    Do you have a schematic diagram for the multimeter? Can you post it?
  20. KrisBlueNZ

    linear mode 10A MOSFET current source

    Hi and welcome to the forums. Your post is very short on information. For a start, how about answering these questions. 1. WHY do you want the main dissipating component to be a resistor? 2. Do you just want to reduce the power dissipation in the MOSFET? 3. Why do you want to use a P-channel...
Top