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  1. KrisBlueNZ

    Power supply

    If you're working with a wide voltage range, you may find it worthwhile to use a current controlled driver for the LEDs rather than current limiting resistors. Calculate the LED current at minimum and maximum battery voltages using your chosen current limiting resistors. You'll find the...
  2. KrisBlueNZ

    Hissing in ATX power supply.

    quantumtangles, a power supply that sounds like a tractor probably has a fan problem. Poke an ice block stick through the fan when it's making the noise, to stop it from turning. If the noise stops, get a new fan. This thread is about a hissing or sizzling noise that comes from the power supply...
  3. KrisBlueNZ

    Choosing a uC

    No, the code isn't identical at all. The source code for a program in a compiled language is probably the same. Is that what you mean? I assume you're comparing an 8-bit AVR to a 32-bit ARM? The major differences are that in an 8-bit device, all the resources are very limited. Typically...
  4. KrisBlueNZ

    Arduino 5V pin supply

    mach7 you've probably figured out the main reason for the warning. Regulators are not designed to be back-fed. That is, you're not supposed to put voltage on the output of a regulator if its input is not powered. What happens depends on the regulator's design. A traditional approach is to put...
  5. KrisBlueNZ

    Mysterious diode identification help!

    Thanks Dave, I've already asked him about those insulating collars. I was hoping someone might have ideas for how to diagnose a problem with the oscillator. It's difficult because you can't test it independently of the load. The load is required for the oscillator to oscillate, and it also sets...
  6. KrisBlueNZ

    How UC3845 Control Pin work?

    Pin 3 on the UC3845 is not an overcurrent sense input. It is intended to monitor the MOSFET current and should be connected to the source of the switching MOSFET (which must be returned to 0V via a current sense resistor) via an R-C delay circuit as shown in some of the diagrams posted. Without...
  7. KrisBlueNZ

    Mysterious diode identification help!

    Hmm. OK, well you've confirmed that C1~6 and the bridge rectifier diodes are OK. Have you screwed the board fully to the chassis? There's a connection on the common of C1 and C2 that looks like it's supposed to be earthed to chassis. If C1 or C2 are faulty, the fuse will blow if that connection...
  8. KrisBlueNZ

    Stepper/sequencing relay circuit

    OK. I'm tending away from using latching relays; I think it will be better to use a few transistors in the control circuit. So RS will have plenty of suitable relays. Each seat has three options - OFF, LOW and HIGH, right? So you can't use just a single relay for each seat. You'll need two -...
  9. KrisBlueNZ

    Power supply

    As some crazy Scottish guy said, "Ye cannae change the laws o' physics, Cap'n". You can't increase the mAh capacity of a battery. Some battery types have higher capacity per unit volume, or per kg of weight. They are also more expensive. You might benefit slightly from using a step-up...
  10. KrisBlueNZ

    Stepper/sequencing relay circuit

    Hi Rich, I don't know if there's anything off-the-shelf that will do what you want. I wouldn't use the word "stepper" in your descriptions or your google searches. In the electronics field, "stepper" is a type of motor that rotates in small angular increments. It's not too difficult to design...
  11. KrisBlueNZ

    Hissing in ATX power supply.

    tweakjunkie, that's a great attitude. I often spend much more than an "economical" amount of time trying to fix things. As well as learning about electronic products, learning about how components fail and which brands and types fail often and in what way, the reward of diagnosing a problem...
  12. KrisBlueNZ

    Component help

    It certainly would be simpler if you had a PWM on-chip but if pushbutton monitoring and LED control is all the micro is doing, it's pretty trivial to do it all in firmware. Both the pushbutton monitoring/debouncing and the LED control require decision-making and I/O on a timed basis, and...
  13. KrisBlueNZ

    Vizio 42" model #: M420NV - HDMI

    By "the same thing" I meant was it always the same device plugged into the HDMI ports when they failed, but you've answered that - there are three different devices. The ports that have failed have varied, yes, but has any HDMI port ever failed when there was nothing plugged into it? Also, was...
  14. KrisBlueNZ

    Confusing waveform driving PC speaker.

    Thanks for the link. You should have included that with your first post. You should also have told us what you are trying to achieve. So far, all I've been able to tell is that you're just experimenting and seeing what the oscillator module is capable of. Is that right? There's nothing wrong...
  15. KrisBlueNZ

    Audio Modulator Noise

    Perhaps you would save the attitude until after you've responded to all the questions I asked you in my previous post on this thread?
  16. KrisBlueNZ

    Confusing waveform driving PC speaker.

    You changed the DC blocking capacitor from 0.1 uF to 100 uF without making any other changes, and still got the same waveform across the speaker? What are the characteristics of the frequency generator? It may have a coupling capacitor in it as well. At the least, we need to see the schematic...
  17. KrisBlueNZ

    Chat_Ghosty's PSU

    You're right that you don't need 1000 uF on the input if you're powering it from a source that's already DC. The actual value is not that important. You could just as easily use a 0.1 uF, the same as the capacitor on the output. Those capacitors are needed by the regulator, to ensure stability...
  18. KrisBlueNZ

    Confusing waveform driving PC speaker.

    You haven't answered my main question: what is the purpose of all of this? I'm not trying to be nosey. Knowing more about what you want to do may help us give you better advice. I don't know what the specified input voltage for the Aux inputs is. It might be listed among the specifications in...
  19. KrisBlueNZ

    Chat_Ghosty's PSU

    You can learn a lot from failing when part of your circuit doesn't work as you expected. But you won't learn anything from a circuit that doesn't work at all because a small fault completely prevents all of it from doing anything useful, or which blows MOSFETs constantly. You also need to learn...
  20. KrisBlueNZ

    Chat_Ghosty's PSU

    Are you trying to design a mains-powered switching power supply? I've re-read this thread and it seems you were talking about a problem with a small power supply with just 5V and 12V outputs. Now you want to design a new one from scratch? I don't want to sound insulting, but you're way out of...
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