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  1. KrisBlueNZ

    Battery charger gismo

    Cool Trevor :-) Yeah, polyswitches aka polyfuses etc have been around for over a decade now. They're good for reducing service call-outs - once the fault is fixed, everything returns to normal. I know what you mean about forgetting something every day! I used these things extensively in my job...
  2. KrisBlueNZ

    digital measuring wheel with two independent readouts

    Hi there and welcome to Electronics Point :-) I think that's probably workable. You may need to match the polarity of the two counter inputs. Also, how short are the segments you want to measure and how many pulses per revolution do you get from the wheel? If the answers are "short" and "not...
  3. KrisBlueNZ

    Help with Magnetek Model 6415 Power Converter

    The battery is not connected to the output of the rectifier. The power supply is not intended to float charge a battery - it just has a transformer with a centre-tapped secondary and two diodes (see the schematic linked in post #1). There is no regulation. To the OP: Can you put your location...
  4. KrisBlueNZ

    preamp led driver help

    Why did you do that? We've said that the op-amp circuit might work, and I've given you some alternative ideas. So you tried something different. And it didn't work. Why are you telling us this? With wire and solder. Connect one wire to the middle tag, and the other wire to either of the end tags.
  5. KrisBlueNZ

    Battery charger gismo

    They can take a while to open, depending on the ratio between the actual current and the trip current. If the actual current is only slightly higher than the trip current, they can take minutes to open. If it's several times the trip current, they open in a few seconds. They're specified with a...
  6. KrisBlueNZ

    preamp led driver help

    The 10k one
  7. KrisBlueNZ

    Z80 Computer

    In case you're interested, here's the usage summary for a monitor I wrote a loooong time ago for a "utility card" I made for the Apple IIe. Commands: . Adr Display double-byte at Adr as a pointer ? Value Base conversion. Prefixes are: No prefix = Hexadecimal input...
  8. KrisBlueNZ

    Z80 Computer

    Your schematic looks reasonable at first glance. Just a few random comments. I think you've got your reset polarity backwards. Probably should drive the UART's reset from a logic output, not from the RC circuit. What kind of Z80 can be clocked at 10 MHz? Not the original one... You'll have...
  9. KrisBlueNZ

    Help with Magnetek Model 6415 Power Converter

    Hi there and welcome to Electronics Point :-) That "converter" is a full-wave rectified power supply without smoothing. It's "DC, Captain, but not as we know it". The output voltage consists of a line of camels' humps, not a flat DC voltage, as shown on the right in this picture. As the manual...
  10. KrisBlueNZ

    I'm back - a new circuit for the mini-golf course

    There's no problem with detecting a short pulse. You can use any kind of latch or flip-flop. You can make one from two transistors (Google bistable multivibrator), logic gates (Google SR latch or SR flip-flop) or an IC such as the CD4013, CD4027, or 74(HC)74. The voltage on your white wire...
  11. KrisBlueNZ

    Battery charger gismo

    Is it a PTC resettable fuse? Something like http://www.digikey.com/product-detail/en/RHE1500/RHE1500-ND/467783 ? Can you post a photo?
  12. KrisBlueNZ

    preamp led driver help

    No, the resistors should be 100k and 10k. Roughly. You want around 0.5V on pin 3. How do you know your phone only outputs 1V p-p? What else can you tell us now that would help us to help you and avoid wasting time?
  13. KrisBlueNZ

    preamp led driver help

    No, it needs to be set near the bottom of its range. Pin 3 should sit at about 0.5V for best sensitivity. You could replace the pot with two fixed resistors, e.g. 100k and 10k, if your supply voltage is stable at 5V. My circuit in post #7 is all you need, provided that the iPod can generate at...
  14. KrisBlueNZ

    Potentiometer to control motor speed

    Say you have a 10k linear pot set to mid-position. The two resistors in your diagram will be about 5k each. The motor will be in parallel with the bottom one. Say the motor draws 0.5A when connected directly across the battery. (You can measure this with a multimeter.) And let's pretend that...
  15. KrisBlueNZ

    Clock failure

    I'm not sure if this will help, but the Linear Technology LT3012 (http://www.linear.com/product/LT3012), available from Digikey (http://www.digikey.com/product-detail/en/LT3012EFE%23PBF/LT3012EFE%23PBF-ND/1620147) is ideal for this application, apart from its tiny, fiddly package. It's rated...
  16. KrisBlueNZ

    preamp led driver help

    Hmm. I don't know. It would be interesting to know for sure though. It's not hard to create a ~0dBm waveform and transfer it to an iPod, and test it (probably into a 33 ohm resistor - these headphones and ear buds are usually 32 ohms I think). I don't have an iPod myself. I have a Samsung...
  17. KrisBlueNZ

    preamp led driver help

    OK, cool. With the emitter follower and biasing removed, the simplified circuit will need about 2V peak-to-peak to saturate the transistor properly, I estimate. If the iPod can put out over 2V (whether you meant 2V peak-to-peak, 2V peak, or 2V RMS), that will be enough. Thanks for your input :)
  18. KrisBlueNZ

    preamp led driver help

    What distance are you hoping to achieve between the phone LED and the ATtiny? Without a tuned circuit, the receiver will be very susceptible to other light sources. That's why IR remote controls use a carrier frequency.
  19. KrisBlueNZ

    preamp led driver help

    Nice work Adam :-) I wasn't expecting anyone to simulate it! Actually my main concern was the input signal voltage. You've used 1V RMS, have you? I'm not sure that an iPod can produce that much signal. I expected the first transistor's base voltage to be closer to 1V than that. What voltage do...
  20. KrisBlueNZ

    Intermittent Operation!

    Hello and welcome to Electronics Point :-) Usually when semiconductors fail, it's permanent. It's possible, but unlikely, for modern semiconductors to become intermittent. Your problem sounds like a mechanical problem such as dry joints. Please let us know what you find. Feel free to upload...
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