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  1. flippineck

    Can this be repaired by a complete novice please? Basic circuit repair?

    Really anything'll do to practice on. Even just small bits of old copper, bits of wire, whatever.. just to get the feel of it. First joint you ever try teaches you 50% of soldering, 2nd try gives you the next 25%, 3rd try the next 12.5% etc sort of like the law of diminishing returns.. any...
  2. flippineck

    Low power bistable latch arrangement

    The J3Y transistor will switch states twice a day, let's say 'off' 9am & 'on' 5pm. So if the relay coil on the timer module is replaced with a suitably high fixed resistance, I should be able to get a suitable signal off the J3Y's collector to drive the mp3 player trigger when it falls to near...
  3. flippineck

    Can this be repaired by a complete novice please? Basic circuit repair?

    Find an old junk transistor radio or something & have a go desoldering / resoldering parts first - doesn't matter what to what - just for practice. Really helps at first. If you've really no experience at all you'll burn some pads right off the board the first few times and fry some...
  4. flippineck

    Can this be repaired by a complete novice please? Basic circuit repair?

    Have you got a very fine hand held drill, like a 'Dremel' or similar? Those tiny (1mm and less) drill bits, burrs, and soft, fine rotary wire cup brushes would be very helpful for very carefully tidying up the board and removing corrosion before resoldering. Careful not to detach any copper...
  5. flippineck

    Low power bistable latch arrangement

    Good point.. it would depend upon the state at power on as to whether the timer ended up opening the door in the morning and shutting it at night, or the other way round.. I could include a momentary push button to manually feed a pulse to the bistable, so I could flip the state independently...
  6. flippineck

    Low power bistable latch arrangement

    I have a timeswitch module that provides a TTL voltage signal to the 70Ω coil of a SPDT relay. One end of the relay coil is fed with +5V from a buck converter chip, which in turn gets it's power from a 6V battery. The other side of the relay coil is connected to 0V (common to battery and buck...
  7. flippineck

    Supercapacitors anyone?

    Been working on a mini digger recently, electrics have been a nightmare, all became clear eventually - several leads despite being visually perfect & checking out at below 1 ohm on the multimeter, were going up to high resistance but only when larger currents were applied. Worth checking for...
  8. flippineck

    What thermal fuse do I need.

    Looks like the outer case will remain live after operation if connected one way, but not if connected the other way round. Always wondered what was inside these.
  9. flippineck

    Current transformer

    Bertus - as far as I can figure it out, if your annotation uses ordinary diodes then whatever is coming out of the coil and burden resistor, is clamped to no more than 0.7V above or below the supply, so the Arduino will never see lower than -0.7V or higher than 5.7V on it's input pin - I *think*...
  10. flippineck

    Power switching relay

    The 2kW inverter should be ably to supply up to, just over 8A whilst there are only a few small appliances connected. For instance a couple of LED light fittings switched on and a mobile phone charger or two, maybe a refrigerator, dare I mention a TV. That would generally be the state the system...
  11. flippineck

    Power switching relay

    The load is a small workshop power supply incorporating a few lighting circuits and power ring with a few 13A UK switched mains power outlets fed by a 2-breaker consumer unit, so the load would vary according to what people plugged in & switched on at any given time. I could limit the current...
  12. flippineck

    Power switching relay

    Rough idea attached. As shown, the diesel generator 'hoists itself' onto the main ring by supplying the coil with it's own 240V when it comes on line. I'd also considered controlling the coil fully from the Arduino. The smaller inverter power supply is left running to handle small loads and act...
  13. flippineck

    Power switching relay

    I've been discounting automotive relays because I was worried they would mostly be designed with 12 or 24 V DC in mind, and putting mains voltage on the contacts would be using the device out of spec. I notice the phrase "N.C. mirror contacts" mentioned in Whonoes' link - sounds like it's a...
  14. flippineck

    Power switching relay

    I used to come across contactors a lot many years ago, working in a panel builders shop.. more substantial yes, but they always seemed to come in 2-terminal NC or NO types, never dual throw, & that's something I need for my current project. I'm using it to choose between two different supplies...
  15. flippineck

    Power switching relay

    Trying to find a DPDT non-latching relay with contacts rated 250 V AC / 40A and ideally a coil able to operate at either 5V DC, or else around 240 V AC Closest I have found so far is the 20844-85 at: https://deltrol-controls.com/sites/default/files/pdf/data-sheet/270-275 Series Data Sheet.pdf...
  16. flippineck

    Current transformer

  17. flippineck

    Current transformer

    Is that suppression of noise from, and stabilization of potential variations on, the power supply, so that the choice of value of the capacitor would depend only on the characteristics of the reference power supply? I can't decide whether to use 100 nF as you suggest, or 10 μF as in the Emon...
  18. flippineck

    Current transformer

    Thanks for your patience Harald, I've gone over it all a few times & I think I now better appreciate post #10 One thing that for some reason wasn't clear to me at first was that the current in the burden loop depends entirely on the size of the primary current and the turns ratio, the...
  19. flippineck

    Current transformer

    Sorry it was the two 100Ω burden resistors, and the 171Ω internal resistance I was wondering about all 3 being in parallel. Yes those potential divider resistors are very fat! No other reason than I liked the look of the ebay seller & the price was fine. I was planning on running the CT &...
  20. flippineck

    Automatic bicycle hub gear changer using servo

    I recall having these type of gears on a kids bike years ago. There was a dinky little chain that snaked out of the end of the axle, turned 90 degress to face forward, sliding over the bevelled bore of the axle, and then connected via a tiny turnbuckle to a cable pull which went to a thumb...
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