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  1. KrisBlueNZ

    voltage divider with diode

    And to answer your question specifically, no, you never connect a diode in a speaker circuit. That will cause distortion (more or less, depending how you connect it). A diode will not compensate for the speaker resistance changing with frequency. You may have misunderstood what you heard. If you...
  2. KrisBlueNZ

    Re-wiring a powered Subwoofer

    I think you were right the first time. That signal is used as a power source. It goes to several places - it controls a front panel LED, it goes into the mute circuit, and it goes into the protection circuit - but none of those circuits use it in any clever way. I think it's just a standard +12V...
  3. KrisBlueNZ

    Voltage conditioning circuit

    Hello and welcome to Electronics Point :-) What are you doing with the signal after it's been linearised? If you're converting it to digital, it would be better to do the linearising in the digital domain. You said that the mapping is "more like a log curve". So it isn't actually a log curve...
  4. KrisBlueNZ

    Voltage Regulator Heatsink

    Nice explanations Merlin :-) BTW the data sheet says: "Power Dissipation ..................................... Internally Limited" and "Thermal shutdown disables the device when the die temperature exceeds the 125°C maximum safe operating temperature."
  5. KrisBlueNZ

    home made digital speedometer

    Hi there and welcome to Electronics Point :-) You should be able to get a bicycle speedometer pretty cheaply. That's my first thought. If you really want to do it yourself, you'll need a microcontroller such as an 8-bit PIC or AVR. These can be programmed in C or assembly language...
  6. KrisBlueNZ

    substitute 4558 op amp for guitar compressor?

    They're not the same. The main difference is the GBP (gain-bandwidth product) but this varies significantly between manufacturers. A clear example is STMicroelectronics, who manufacture both types. Their 4558 has a GBP three times higher than their 1458. I think, from memory, that the 1458 is a...
  7. KrisBlueNZ

    Need Help with Clapper Circuit

    Hi Elliot and welcome to Electronics Point :-) That's a horrible clap detector design. Both the hardware and the firmware are really awful. I think you should be able to find a much better design. But to answer your question, yes it's pretty easy to change the firmware so that it pulses the...
  8. KrisBlueNZ

    Trouble with tribbles.. erm, timers.

    You intend to have 20 different brightness levels for each LED, right? I guess you will be using PWM, as well as multiplexed drive? Have you considered the speed requirements? It may impact your choice of language and/or micro! So you have 107 tri-colour LEDs, right? That's 321 control signals...
  9. KrisBlueNZ

    help with a 4017

    No. For various reasons. Not the least of which is that it won't work! A CD4017 might be able to provide 24 mA (I'm doubtful) but only at a reduced output voltage. CD4000 devices have typical output resistances of over 100 ohms. At 24 mA that's a drop of at least 2.4V, probably a lot more...
  10. KrisBlueNZ

    Wireless Headphones

    It might be worth a quick look inside. But if you value your time, it's almost certain to be more economical to replace it. Have you found a suitable replacement power supply?
  11. KrisBlueNZ

    Wireless Headphones

    It sounds like the power supply is starting up, then detecting a problem and going into a lock-out state. Have you changed anything about the AC supply into the power supply? It could be the optocoupler in the power supply, but it could be a lot of other things too. You could open it up and...
  12. KrisBlueNZ

    light automatic on off using pic 16f870

    Adding hysteresis is pretty easy. #define HYSTERESIS 10 // Distance from centre to each threshold #define CENTRE 80 // Centre value (half way between thresholds) unsigned char adcvalue; void main() org 0x10 { adcon0 = 0x85; adcon1 = 0x01; // ADC gets its reference voltage...
  13. KrisBlueNZ

    light automatic on off using pic 16f870

    You are setting ADCON1 to 0x01. This sets the PCFG bits to 0001. If you do this, you must provide a positive reference voltage into RA3. If you're using VDD as the positive reference for the ADC, you should set the PCFG bits to 0000, i.e. ADCON1 = 0x00. The ADC will use VDD as its positive...
  14. KrisBlueNZ

    Ring Modulator (dalek emulator)

    Yes, but not what you think. I lost interest in sci-fi (and most fantasy, really) in my teens. But I remember helping a friend with a circuit called the "Cylon Voice". It was a project in a magazine, Electronics Australia I think, based on an XR2206 used as a ring modulator, with a carrier...
  15. KrisBlueNZ

    Hello, Welcome! (Introduce yourself)

    Hi kpatz I wish we could send you some of our heat! Not just because it's so cold there... it's too hot down here! It's great to have you on board here. All of your posts have been accurate and helpful. And you can spell, and write clearly. I hope you stick around!
  16. KrisBlueNZ

    Emergency Power Supply Schematic Diagram

    Exactly. In both the boost and flyback converters, energy is delivered to the load when the switch turns off and the polarity of the voltage(s) across the winding(s) reverses. In the flyback converter, the output voltage is supplied entirely from the flyback voltage, whereas in the boost...
  17. KrisBlueNZ

    How to get a strong signal over a long distance

    Are you trolling us? Steve was pretty clear (emphasis mine):
  18. KrisBlueNZ

    Emergency Power Supply Schematic Diagram

    Functionally, yes, but a BJT has a better-defined input voltage threshold. You would be best to use a shunt regulator such as a TL431. These have a very accurately controlled input threshold voltage. Feed it from the battery voltage via an adjustable voltage divider (e.g. a multi-turn trimpot)...
  19. KrisBlueNZ

    adc temperature problem

    Great answer kpatz. Did you get the PM I sent you? Just below the Electronics Point banner at the top of any page, at the right side, click on Private Messages.
  20. KrisBlueNZ

    Emergency Power Supply Schematic Diagram

    Nope. Q3's source voltage is about 10.6V higher than Q2's source voltage! And Q3's source cannot supply more than about 7~8V (the 12V input voltage minus its gate-source voltage) even if Q2 wasn't pulling its gate voltage down.
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