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  1. KrisBlueNZ

    6v SLA charger

    In addition to what Steve said, I recommend adding a diode (e.g. 1N400x or 1N540x) across the LM317 to protect it from damage if the input supply is removed - connect the anode to the output pin and the cathode to the input pin - and a low-value resistor e.g. 100Ω in series with the base of the...
  2. KrisBlueNZ

    Chicken Coop Door Opener

    Thanks Adam :-) Re powering, how about a 5V wall wart? http://www.radioshack.com/product/index.jsp?productId=21779286 Re the limit switch. I would try to hack into the existing one in the controller, but I can see why that might be unwise. It's just that mounting and adjusting them can be...
  3. KrisBlueNZ

    Chicken Coop Door Opener

    Yes, you should be able to work around that limitation, but you need to change the structure of the program so it can do other things while the timer is running. For example, responding to the manual control button. The details of the timer handling should, if possible, be invisible to the main...
  4. KrisBlueNZ

    Voltage to current converter circuit

    I don't think so, but I'm getting out of my depth here. I'm waiting for the answers to my questions before I know how deep the water is!
  5. KrisBlueNZ

    Voltage to current converter circuit

    XL = 2 pi f L = 2 × pi × 20,000 × 135 × 10-6 = 17Ω Getting 1A RMS into a 17Ω inductive reactance would require an amplifier with a fairly agile output, I think. It's certainly outside my experience. And I don't think a hard drive servo chip would do it, although it might be a good idea for you...
  6. KrisBlueNZ

    Want to know more applications of step-up DC to DC converter

    You want to make a high-power DC-to-DC converter with an output of 120V at 8A but you don't have an application for it? I wouldn't do that! The usual way is to have the requirement first, then find something that fits that requirement. In answer to your question, there are many useful...
  7. KrisBlueNZ

    Voltage to current converter circuit

    Perhaps he means he wants to feed a 20 kHz sinewave into each inductor, with an amplitude of between 200 mA peak and 1A peak? What is the inductance? The DC resistance? How closely coupled are the other inductors? How much energy will an inductor receive from the inductor opposite it? Will...
  8. KrisBlueNZ

    Broken SMD - need suggestion for replacement

    Hello there and welcome to Electronics Point :-) As you've discovered, capacitance values are not marked on MLCCs (multi-layer ceramic capacitors). You may be able to fix it though... Is it possible to measure the capacitance of the old one? Have you searched the Internet for a service manual...
  9. KrisBlueNZ

    LED problem... Need help!!

    Hi Remater and welcome to Electronics Point :-) I would use a buck switching regulator with output current regulation. For the brake LEDs, at least. You can make these from standard buck converters like these...
  10. KrisBlueNZ

    Designing a Time Delayed Relay

    OK, here are my initial thoughts. These points correspond to these markings on the diagram. 1. The highlighted tracks are at mains voltage relative to the rest of the board so you need to have clearances between the tracks (and all connected component pins) and any adjacent copper and...
  11. KrisBlueNZ

    How do you disconnect these type of ribbon cables?

    I don't know about the first one. It looks like a plug/socket arrangement. I think the second cable is soldered directly into the board. The plastic bits are only there to stop the wires from being bent sharply where they join the board and eventually breaking. If that's the case, you will need...
  12. KrisBlueNZ

    Smoke detector mystery

    Wow, that's a pretty deep mystery alright! I agree that the inductance and/or resistance of the wires would be the reason why the smoke detector reports battery low. I've had problems with smoke detectors being very fussy about the condition of the battery myself. I don't know why the...
  13. KrisBlueNZ

    Sensitive photodiode circuit help

    Then you could either scan it, or take a photo of it.
  14. KrisBlueNZ

    Sensitive photodiode circuit help

    Hello and welcome to Electronics Point :-) You could start by posting the schematic diagram of your circuit.
  15. KrisBlueNZ

    Multimeter resistance measuring not working

    The current measurement problem is probably caused by a blown fuse. Yes, even cheap nasty multimeters have fuses on the current ranges! Have a look inside the multimeter for a cylindrical glass (or possibly ceramic) fuse and see whether you can see the wire inside, and whether it's broken or...
  16. KrisBlueNZ

    I am new here

    Hi Chris and welcome to Electronics Point :-) That's a good question. It could probably go in General Electronics Chat or Electronic Projects. Since it's a project you're working on, probably Electronic Projects would be best.
  17. KrisBlueNZ

    a circuit that will indicate when a contact is broken?

    Yes, all agreed. The Darlington has two characteristics I can see that are advantages in some situations: The Darlington connection forces all of the current through the load path, so no current is "wasted"; The alternative circuit doesn't limit the base current into Q2. This current is...
  18. KrisBlueNZ

    a circuit that will indicate when a contact is broken?

    Yes, although you can't completely eliminate the drain on the battery. You need some current flowing through the plate and foot. Here is a circuit that has a very low current consumption in the OFF state. This circuit uses two transistors connected as a Darlington pair. This configuration has...
  19. KrisBlueNZ

    Using OP484 as Comparator

    Thanks for the pointer Laplace! Good information there. Here's a direct link: http://www.analog.com/static/imported-files/application_notes/AN-849.pdf
  20. KrisBlueNZ

    Aiwa NSX 3500 CD Tray problem

    Is the eject button broken? Does it click normally when you press it? What happens if you push the tray in slightly? Normally this will make a CD player close the tray.
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