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  1. KrisBlueNZ

    New Member here

    Hi James and welcome to Electronics Point :-)
  2. KrisBlueNZ

    2g to 3G?

    Not necessarily a silly question, but one with almost no information. Are you talking about modifying a cellphone? A cellular modem? Something else? I very much doubt that any upgrade kit would be available. Have you tried a Google search?
  3. KrisBlueNZ

    LED switch wiring

    The specifications on the auction page give the "light voltage" as 220V. So if it's an LED, it will have a large-value resistor in series with it. It might also be an incandescent lamp or a neon, but the auction title does mention "LED".
  4. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    Steve, are you sure Schottky diodes have lower capacitance than fast recovery diodes? I suggested back in post #14 that abuhafss use a UF4002 or higher because the 1N5819 has a maximum reverse voltage of 40V which is uncomfortably close to the output voltage. Of course you can get Schottky...
  5. KrisBlueNZ

    Divide by n, where n is selectable

    Great suggestion from Laplace. I assume you want to use CMOS 4000-series devices. Check out these data sheets. Some of them aren't suitable, but some of them definitely are. CD4029: http://www.ti.com/lit/ds/symlink/cd4029b.pdf CD4022: http://www.ti.com/lit/ds/symlink/cd4017b.pdf CD4018...
  6. KrisBlueNZ

    Divide by n, where n is selectable

    Hi there and welcome to Electronics Point :-) How about a binary counter and a magnitude comparator? Feed the divisor into one side of the magnitude comparator and reset the counter when the count matches the divisor and the magnitude comparator output goes true. Detect wraparound by NORing the...
  7. KrisBlueNZ

    Need Tech Brains!

    Hi there and welcome to Electronics Point :-) That's a very interesting idea. It wouldn't be easy, and it wouldn't be cheap, but it would be very cool. I was going to offer a lot of suggestions on how to detect the pieces, and which parts of your suggestions would be less difficult, more...
  8. KrisBlueNZ

    Adding Aux input to older car stereo

    Whether they're glued or not depends on how the board was assembled. If it was flow-soldered, which is what it looks like (I think - I'm no expert on this), then they should be glued, but don't assume that they are. Just make connections quickly, and if you need to connect to both ends (you...
  9. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    Why do you say the output diode "has to be" Schottky? What happens if it isn't? Can you repeat the first and third graphs from post #47 but add the waveforms for: Voltage on the drain of the MOSFET (Q1), and Current through the inductor.
  10. KrisBlueNZ

    Adding Aux input to older car stereo

    OK, here's what I suggest. Cut the two tracks between PA51 and R507 and R508, at the points marked with the red Xes. A good way to do this is using a pair of sharp side cutters, held vertically, with one point anchored to the board in the area indicated by the "A" and the arrow. You can...
  11. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    I don't know why there's so much noise when you use a polarised COUT. What ESR have you specified for the capacitor? Also you could temporarily try a 1N5819 for the output diode to see whether it makes any difference. The red trace is just upside down. See it varies from about 0 µA to about...
  12. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    Yes, the UC3843 will work. There are lots of designs around. http://www.google.com/search?q=UC3843+boost+converter&tbm=isch I couldn't say which one is best. Avoid any designs that have the MOSFET's source grounded. It should go through a current sensing resistor. The ON Semiconductor data...
  13. KrisBlueNZ

    Component suppliers

    Thanks guys. I've updated the resource.
  14. KrisBlueNZ

    Cleaning pots in old analog meters

    I would check for corrosion on the battery holder and battery contacts, and dry joints on the circuit board. Also check that the sockets for the meter probes are clean and tight. Clean the selector switch contacts with isopropyl alcohol and a cotton swab. Clean both the stationary and moving...
  15. KrisBlueNZ

    Whats this please?

    The "varnish" is probably conformal coating. It's put there to protect the board and circuitry from moisture, corrosive atmosphere, etc. There's no obvious problem visible in either of your photos, and the "board stops if I touch the crystal" is not a fault. I can't find any data on the...
  16. KrisBlueNZ

    Component suppliers

    Thanks Steve, Adam and Dan. I've added all of your suggestions. Can you guys provide comments about any of the suppliers you've used? For example, the type of components the specialise in (if any), the size of their range, or anything else relevant to people deciding who to use? Adam, what's...
  17. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    It's mostly affected by the zener. The supply voltage only comes into it because it affects the falling voltage threshold at the 555's input, which is 1/3 VCC. That's why for every 1V change in input voltage, you get a 0.333V change in the output voltage. Unless you add the zener on pin 5...
  18. KrisBlueNZ

    Adding Aux input to older car stereo

    Thanks for the pointer to All Electronics; I've added it to the resource. Can't help with the disassembly question though.
  19. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    The 555 won't switch back ON again until the voltage drops below the lower trigger voltage, which is about 4V. Also, there's a 1N914 in series with the zener, which would make the trigger voltage about 4.6V. The voltage in the simulation, 3.8V, is probably lower than 4.8V because of the...
  20. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    I just graphed the efficiency using the formula shown in red at the top of the graph. You'll see that it's low during startup but levels off around 85%. I had to increase CIN from 100 µF to 1000 µF otherwise there was too much "wiggle" in the efficiency trace. This is also why it takes about 10...
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