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  1. KrisBlueNZ

    Shorted DC drive transformer

    Jerry, that was a rather rude reply to tryppyr. We are all volunteers and just trying to help. The Tamura 3FD-224 is a very small mains transformer with 24V and 12V secondaries, rated at 1.1 VA. Presumably it is used to power the controller circuitry. If you got a decent spark from it, you...
  2. KrisBlueNZ

    advice for device repair

    It depends on the device. A stereo amplifier is a simple example. These will typically have a power supply, a preamplifier stage, and a power amplifier stage, and these sections can be tested independently to some extent. You can measure the power supply output voltages with a multimeter, and...
  3. KrisBlueNZ

    5 second time delay pulse

    If you need more guidance, have a look at the design I posted in post #5 on this thread: https://www.electronicspoint.com/want-build-2-event-delay-timer-controller-t256873.html The design uses a 556, which is a dual 555. The first half is used for the initial delay, and the second half...
  4. KrisBlueNZ

    Help on circuit

    I understand and agree with your description of how the LED drive circuit works. And I agree that it's a buck converter, even though it doesn't immediately look like one. And I'm sure it works fine. I'm just raising a concern about limiting the maximum current and avoiding saturation in the...
  5. KrisBlueNZ

    Mux/Dmux

    The nine diodes make a crude encoder. If one of the six inputs is active (positive voltage), the circuit generates a three-bit binary number that corresponds to the number of the input that's active. If no inputs are active, the resulting binary number is 0. This arrangement, where the three...
  6. KrisBlueNZ

    Accelerometer HELP!

    Yes, I was being facetious when I said "Piece of cake", hence the :-/ emoticon! I agree with davenn. You would have to approach a large microelectronics organisation and wave a BIG wad of cash under their noses.
  7. KrisBlueNZ

    Mux/Dmux

    Well, you could save a lot of outputs if you used a CD4017 (see http://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/CD4017BC,%20CD4022BC.pdf) to drive one end of the cable. It has up to ten outputs, but can be configured to use any number of them, with one output active at a time. It...
  8. KrisBlueNZ

    Main chip to use?

    Yes, this sounds like a job for a Microchip PIC or an Atmel AVR. Both are well-supported with development systems, and if you choose an AVR you can develop your hardware and software with an Arduino platform. I assume you want an LED display? And you will want at least one pushbutton, and a...
  9. KrisBlueNZ

    Mux/Dmux

    Do you have a PLC? Can it do the automatic testing? Will your test jig have connectors for both ends of the cable? Or do you need one jig at one end, and a separate jig at the other end? If it's possible, your simplest test setup would be to have six PLC outputs driving the six cables at one...
  10. KrisBlueNZ

    HELP: Need circuit for high current control based on analogue voltage

    I should have suggested: you may find it a lot easier to keep the magnet stationary and move the coil around. Much less mass to accelerate.
  11. KrisBlueNZ

    Help on circuit

    I think I see what you're doing there. I guess those sinewaves labelled L1 and L2 are supposed to be inductors? So you turn the MOSFET ON, current builds in the inductor, then you turn it OFF, and the current falls back to zero. You just need to make sure that (a) the inductor doesn't saturate -...
  12. KrisBlueNZ

    Triangulate

    As Dave says, the problem with measuring distance using radio waves is that they travel extremely quickly, so your receiver would need to measure extremely small timing differences. GPS receivers do this, but there is a lot of high-tech design involved. Location services for cellphones, as far...
  13. KrisBlueNZ

    HELP: Need circuit for high current control based on analogue voltage

    Hi Tim and welcome to Electronics Point :-) You can control the current through a load (instead of the voltage across it) using an amplifier whose feedback is taken across a resistor that's connected in series with the load. The problem is that you cannot simply apply a current to an inductor...
  14. KrisBlueNZ

    Accelerometer HELP!

    Android wristwatch phones are available with accelerometers. You can write your data logging software as an Android app and transfer the data using Bluetooth or WiFi. Piece of cake! :-/ http://www.alibaba.com/product-gs/1408468153/Latest_wrist_Android_smart_watch_mobile.html?s=p I DO NOT...
  15. KrisBlueNZ

    Interesting Circuit

    The MAX307 (not MAXDG307) is not suitable for this application. It is designed for signal multiplexing, not switching significant currents. The ON-resistance of each switch is typically 60 ohms, maximum 100 ohms at room temperature. That circuit has two switches in series for pulse to the relay...
  16. KrisBlueNZ

    Automated Sliding Door

    See 1. http://www.powerstream.com/Wire_Size.htm 2. http://www.amplepower.com/primer/gauge/ 3. http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html The maximum expected current is 5A. In this case I would design for at least twice that. According to (1), 20 AWG can carry 11A but based on...
  17. KrisBlueNZ

    What The Heck Is He Talking About??

    Right. I don't agree with the idea of relying on the input capacitance of the pin itself. I would always use an explicit external capacitor.
  18. KrisBlueNZ

    What The Heck Is He Talking About??

    Yes, this method will work. It's designed to detect the position of a three-position switch (e.g. an ON-OFF-ON switch) where the changeover contact is connected to one of the end pins in the end positions, or nothing in the centre position. If the end pins are connected to VCC and 0V, then the...
  19. KrisBlueNZ

    Help on circuit

    Even with PWM you need SOME form of current limiting. For example if your PWM is running at 50%, what is your average (mean) LED current? 50% of what? I think your schematic in post #43 relies on the inductor for current limiting, but I guess you've changed the schematic since then. Could you...
  20. KrisBlueNZ

    Help on circuit

    Nice to hear from you again Fish :-) I don't know of any reason not to mix LEDs with different forward voltages in a series string, if you want the same current through them. It could work out quite well, for example if you have an equal number of red and green LEDs that all need to be driven...
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