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  1. KrisBlueNZ

    Chicken Coop Door Opener

    Any fuseholder that holds a 5x20 mm fuse will do the job. It depends what style you want and how safe you want it to be. You can use two simple clips soldered into the circuit board, or a block, or a full holder. Some holders can be mounted in a panel for easy fuse replacement. It's up to you...
  2. KrisBlueNZ

    LDR controlled Lamp from a 220VAC

    Yep. You can use my design that I linked to in post #3. Just replace the motor with the relay coil. You need to leave the diode in place because the relay coil is inductive and generates a "back EMF" voltage that could damage the MOSFET if it's not clamped using the diode. You can use a much...
  3. KrisBlueNZ

    does this seem right?

    You can find schematics in the data sheets. You just need to know where to look. I've listed some devices that look suitable further down in this post. But I want you to understand what you need, so you can be sure these devices will do what you want. You have a requirement to be able to drive...
  4. KrisBlueNZ

    instrumentation amplifier

    Why don't you check your diagram carefully against the correct schematic for a three-op-amp instrumentation amplifier. You will see where you went wrong. If you had done this when I pointed out your first error, you would have saved a lot of time. Do a Google search for instrumentation...
  5. KrisBlueNZ

    instrumentation amplifier

    Oops I spoke too soon. You have the inputs on the rightmost op-amp reversed.
  6. KrisBlueNZ

    Sense sound and fade LED

    OK, here's the circuit I've come up with so far. I'm posting it here in case you're still interested, so you can get an idea of what would be involved. If you want to go any further, answer my questions in post #6.
  7. KrisBlueNZ

    instrumentation amplifier

    Yay! You've got the circuit right. Now does it do what you expect?
  8. KrisBlueNZ

    ADN8831 no cooling mode

    OK, try again. This time, post the schematic with the TEC in it!
  9. KrisBlueNZ

    instrumentation amplifier

    You haven't corrected the circuit error on the inverting input of the bottom op-amp. You haven't identified VREF; you have just marked some voltages on the diagram. Look at the LM324 data sheet. In the specification table there's a line called VOH. It gives the guaranteed minimum high output...
  10. KrisBlueNZ

    Dynex DX-L42-10A Intermittent Issues

    OK, that's fine. There's no need to measure R502. I've found a Powerpoint-type document on the Sanken SSC9500 (N502) but I can't find a full data sheet for it. There's also an error in the schematic which is causing a little confusion. I think it might be worthwhile simply replacing N502 on...
  11. KrisBlueNZ

    instrumentation amplifier

    There is no reference voltage marked in the diagram. Please add a marking for it, and update your diagram with the correction you made for the inverting input of the bottom op-amp. As long as you use a higher positive supply voltage, your amplifier will accept voltages in the range 0~5V at both...
  12. KrisBlueNZ

    Traffic Lights Circuit Help

    OK, so you can actually do most of the control very simply. Can you define the control signal for the green LED in terms of the input signal? And can you define the amber and red LED control signals in terms of the input signal, along with a timer? It's pretty clear that a five second delay is...
  13. KrisBlueNZ

    Basic beginner questions (voltage reading/resistors)

    P.S. The formula for current vs. R for that current regulator is not exact; the 0.7V is just a nominal voltage. Using that formula, R = 0.7 / I, gives a result of 20 ohms. I recommend you use a 15Ω resistor in series with a 10Ω preset potentiometer ("trimpot") in that position. Initially, set...
  14. KrisBlueNZ

    Basic beginner questions (voltage reading/resistors)

    Hi Les and welcome to Electronics Point :) Your calculations in point 1 are good. You have calculated the voltage that must be dropped by the resistor, and divided that by the current in amps, to come up with a value of 43 ohms for the resistor. But the data sheet says that the forward voltage...
  15. KrisBlueNZ

    instrumentation amplifier

    That circuit is wrong. Check where you have connected the inverting input of the bottom op-amp. Also as Harald says, you will need a higher VCC rail if you want to support 0~5V at your input.
  16. KrisBlueNZ

    Traffic Lights Circuit Help

    This sounds like a homework question so I've moved it to the homework forum. If it isn't, let me know and I'll move it back. Let me clarify what you want. Your circuit has one input, and three outputs - that drive the green, amber and red LEDs in a single traffic light. Is that right? When the...
  17. KrisBlueNZ

    Meg ohm resistors , are opens circuits?

    Yes, in the focus and A1 circuits. We used those chunky blue resistors for all that high-voltage stuff, and I never saw a failure. Those were high-quality high-voltage Philips metal film resistors, and you could use two or three in series to drop several kV IIRC. It's funny that lesser-quality...
  18. KrisBlueNZ

    Dynex DX-L42-10A Intermittent Issues

    OK. That 0V reading on pin 9 is wrong. But I didn't explain how pins are numbered. I've marked up the pin numbers on your picture: Can you confirm that there's 0V on pin 9? Also you said that the pin 1 voltage is 2V. Can you measure it again on a lower voltage range so we get more digits? If...
  19. KrisBlueNZ

    Meg ohm resistors , are opens circuits?

    Connecting resistors in parallel reduces the resistance as Steve just described. Connecting resistors in series increases the resistance by simple addition. A 10M resistor in series with a 4M7 resistor has a total resistance of 14.7 MΩ. Resistors above 10 MΩ are not available in standard...
  20. KrisBlueNZ

    In rush chokes on op amp inputs

    It could do. That would be the reason for the inductors and the tiny capacitor. They won't have any effect at all on the signals you're trying to measure. I think they're just there to reject RF and other high-frequency noise.
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