Search results

Search Forums New Posts
  1. KrisBlueNZ

    Simple Circuit using transistors

    That's good! You're getting close now. Where is the output of that circuit taken from? Why is your input pulse described as being 1 ms wide? It is just a transition from 0V to +3.3V with no duration. The C-R circuit is what generates the timed pulse. There is one component missing from that...
  2. KrisBlueNZ

    Small Circuit needed for New Product Design - Help!

    Debouncing can be done by firmware inside the micro. There are several important differences between LCD and LED displays. LED: They glow, so they can be read in darkness They have a wide viewing angle They are available in 7-segment and "star" styles They draw significant power (probably at...
  3. KrisBlueNZ

    Which voltage transformer for a laser printer

    Great! You might want to place feedback about the transformer having a fault, so other prospective buyers can get an idea of its quality!
  4. KrisBlueNZ

    Where to Purchase Transformers

    Also you can get transformers with multiple secondaries; you could use one secondary as the input and another as the output. Or you could get an over-rated transformer with a 100VAC or 110VAC primary and say a 48V secondary, and under-drive it and use it in reverse.
  5. KrisBlueNZ

    driving analog frequency through a digital component

    Apart from the problem of feeding an analogue signal into a clock input, the general answer is that digital inputs have a threshold voltage. When the applied voltage is above the threshold, it is regarded as high; when it's below the threshold voltage, it's regarded as low. The threshold is...
  6. KrisBlueNZ

    Simple Circuit using transistors

    OK, there are quite a few problems with that circuit. 1. You have connected a voltage source directly across the base-emitter junction of the first transistor. A base-emitter junction behaves like a diode. Look at the current vs. voltage curve of a diode: (That diagram comes from...
  7. KrisBlueNZ

    Simple Circuit using transistors

    Yes that's right. Can you draw up a circuit? Remember that the base-emitter junction of the transistor will clamp its voltage to about 0.7V. If you connect the output of the C-R circuit straight to it, this clamping behaviour will affect the C-R circuit. What would you put between them so the...
  8. KrisBlueNZ

    Small Circuit needed for New Product Design - Help!

    Are you sure a 0.5" display will be big enough to be readable? Can you provide a link to the display you intend to use? It may not be practical to drive it from a 3V battery. As for low power mode, the microcontroller can turn off the displays in the right circumstances. For example, if both...
  9. KrisBlueNZ

    Simple Circuit using transistors

    OK. Start with a C-R "differentiator": (That image is from http://www.electronics-tutorials.ws/rc/rc_3.html) See what happens at the output in response to the input going from low to high? There is a positive pulse whose length is determined by the values of R and C. How can you use one or...
  10. KrisBlueNZ

    Simple Circuit using transistors

    A simple way to convert a step input change into a pulse is with a capacitor-resistor "differentiator" or pulse generator. Feed the input signal through a capacitor, with a resistor to 0V. To calculate the values, choose a convenient resistance, say 10k, and calculate C by rearranging the...
  11. KrisBlueNZ

    Small Circuit needed for New Product Design - Help!

    It would really help if you defined your requirements. But I will describe one way to do what you want, for you to consider. All the logic you need can be easily implemented in a 14-pin microcontroller such as a PIC16F610 (surface-mount version...
  12. KrisBlueNZ

    Need help determining components for a circuit.

    I Googled that part number, SFD106. It's clear that it's a germanium diode. Two sites say it's a UHF/Microwave detector diode; one says it's a "Germanium point contact diode intended as AM demodulator." I haven't been able to find a data sheet, or even the name of any manufacturer. Most likely...
  13. KrisBlueNZ

    Promote a post!

    A really good thread on suppliers for small quantities of PCBs: https://www.electronicspoint.com/threads/custom-pcb.268761/
  14. KrisBlueNZ

    Where to get this object?

    Can you show us pictures of the other parts? The glass bulb and the place where that cylindrical part screws into?
  15. KrisBlueNZ

    PSU Repair - Tevion DVD Recorder

    Good work!
  16. KrisBlueNZ

    Problems with SMPS with TL494, again :)

    OK, the pin 3 voltage is too high. One of the error amps is pulling it upwards. The first error amp has the right voltages going into it, so it must be the second one, on pins 15 and 16 as you suspected. Since you're not using that error amp, you have to disable it by tying pin 16 to 0V and...
  17. KrisBlueNZ

    Alarm reset timer

    The specifications (further down the auction page) say that the leakage current is 16.45 µA, which is three times higher than the Nichicon one that I recommended. In other words, no.
  18. KrisBlueNZ

    Problems with SMPS with TL494, again :)

    The only problems I can see immediately are: 1. The diodes across the main MOSFETs should be rated for more than 1A. 2. The current "limit" is actually an overcurrent trip. 3. The overcurrent detector may not act quickly enough to protect the main MOSFETs if a direct short is placed on the...
  19. KrisBlueNZ

    aduino uno and siemens gsm serial modem

    Hi Ron and welcome to Electronics Point :-) I can't help with the modem but I can suggest you use something better than Hyperterminal (i.e. anything other than Hyperterminal). In my experience, Hyperterminal causes its own problems, as well as being nasty to use. One thing that's worse than...
  20. KrisBlueNZ

    Fluke 8375A is not too stable

    Wow, that's an old meter! How many digits? Please keep us informed Steve.
Top