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  1. KrisBlueNZ

    Basic 555 timer

    He mentioned a relay; I assume that's on the 555 board between the 555 and the output that drives the door latch solenoid.
  2. KrisBlueNZ

    capacitor help

    Hi there and welcome to Electronics Point :-) Yes. They need to be low-ESR types, with a high ripple current rating. They need to have the same or slightly higher capacitance, voltage rating, and temperature rating. They need to fit physically. You should get good quality capacitors, which...
  3. KrisBlueNZ

    "Has it got the Cobalt?" (story)

    I think certain languages are suited to certain types of programming. Back in the day, COBOL was suited to business programming and Fortran was suited to mathematics. In the embedded environment there's assembly language and C, and sometimes Pascal, C++ and Java. And custom languages like PICAXE...
  4. KrisBlueNZ

    Basic 555 timer

    Hi and welcome to Electronics Point :-) Is the door latch circuit powered from the same power supply that is powering the 555 board? Is the power supply properly rated? If the power supply is under-rated, when the relay closes and connects the power supply to the door latch, the extra current...
  5. KrisBlueNZ

    Reverb installation

    Post some photos too.
  6. KrisBlueNZ

    Help with Varactor Diode

    Yes, and yes.
  7. KrisBlueNZ

    Transmit and receive parallel data through radio link

    What do you want to do? You need to describe the project.
  8. KrisBlueNZ

    Help with Varactor Diode

    Now you have the resistor connected to the wrong place. Connect the resistor to the top of the 0.1 µF capacitor.
  9. KrisBlueNZ

    Converting ATX PSU to Bench DC Power Supply

    It's a cheap and popular hack. That guy did a nice job of it too. He added a variable voltage section, which I think is separate from the ATX power supply.
  10. KrisBlueNZ

    Transmit and receive parallel data through radio link

    Sounds like you want a CD4051B. It's a 1:8 design with three control bits. It uses bilateral switches so you can use it as a multiplexer and a demultiplexer. No matches on Maplin but Farnell have it. I don't know what their shipping charges are like though...
  11. KrisBlueNZ

    Chicken Coop Door Opener

    Not that I know of. When you get to the end of the travel, they make a little click sound on each rotation, but they don't stop turning. I don't think the setting will be very critical in this application. A single-turn trimpot should be OK. You could ask the guy you're making this for; he...
  12. KrisBlueNZ

    Help with Varactor Diode

    Not quite. Move the cathode of the varicap to the other end of the inductor, then it's right.
  13. KrisBlueNZ

    Chicken Coop Door Opener

    Hi Dan :-) Well, they both contain a resistive track and a wiper, but they're two different things. A potentiometer has a shaft for fitting a knob, and is designed to be adjusted from outside the case. They are available with logarithmic and linear "law" (logarithmic is used for volume...
  14. KrisBlueNZ

    Help with Varactor Diode

    Yeah, a simple option would be to break the connection from the bottom of the inductor to the 0V rail, put a capacitor (e.g. 0.1 µF) across the break, and apply the control voltage across that capacitor.
  15. KrisBlueNZ

    "Has it got the Cobalt?" (story)

    A post on another thread brought to mind this little story that Lester, the MD of the company I worked for for 20+ years, used to like to tell. Back in the late 1970s, Lester and two partners had formed the company to design, program and manufacture embedded microprocessor-based products for...
  16. KrisBlueNZ

    Re-wiring a powered Subwoofer

    If you want your sound to come out the front left and front right speakers, then I think your connections are all good. If you want the sound to come out of the subwoofer, you need to feed the signal into pin 6, and you should mix both channels together using a 1k resistor from each channel...
  17. KrisBlueNZ

    power supply current match to load

    That should work, but the power supply is a bit under-rated for current or power. The power supply has an output voltage of 18V and can supply up to 1.3A. Power is voltage multiplied by current, so 18 × 1.3 is 23.4 watts. That is the maximum power your power supply is rated to supply, according...
  18. KrisBlueNZ

    Chicken Coop Door Opener

    Keep the pullup resistor (R2, R6, R1) connected to the pushbutton/Hall sensor/LDR at the point where it comes into the board. Then insert a 33k resistor between that point and the PIC pin. Add a 10 nF capacitor from the PIC pin to 0V. In the case of the LDR, you can use C3, 100 nF, as this...
  19. KrisBlueNZ

    Buying ICs off of ebay - I think I finally learned my lesson

    As Bob said in post #2, the problem could be that the voltages you're feeding into the inputs are outside the allowable range. This range is 0V to (VCC - 1.5V) at 25°C, and 0V to (VCC - 2V) over the full temperature range. So at VCC = 5V, if either (or both) of the inputs are higher than 3V, the...
  20. KrisBlueNZ

    Chicken Coop Door Opener

    That schematic looks good Dan. Are the LDR, the Hall sensor, and the manual pushbutton going to be near the circuit board and connected with short leads? If so, fine. If the leads are going to be longer than a metre or so, you should include some components to protect the PIC from noise and...
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