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  1. KrisBlueNZ

    Highest sensor read question

    In case you're interested... That's a design that I came up with for someone on a different thread who wanted to compare the received signal strength indication (RSSI) voltages from four radio receivers and choose the highest one. The op-amps used with small MOSFETs as separate voltage...
  2. KrisBlueNZ

    Chicken Coop Door Opener

    The timer itself is a "variable". You can read and write the count register of the timer, but it is special in that it increments by itself 3906.25 times per second; normal variables only change when the program code changes them. It's called a "volatile" variable. But that's not important...
  3. KrisBlueNZ

    The whole reason I am here... :)

    The "transformer" in the line filter area is a "common-mode choke"; it's part of the filtering circuit that protects the circuit from incoming disturbances on the AC mains and reduces the noise injected onto the AC mains due to the switching action of the circuit. It doesn't provide any...
  4. KrisBlueNZ

    Chicken Coop Door Opener

    The schematic looks good. OK. You understand that a microcontroller follows instructions, one by one, in sequence. Any program is a sequence of steps and branches. The micro's processing core can't literally be doing two different things at once. But there are techniques you can use to make it...
  5. KrisBlueNZ

    Chicken Coop Door Opener

    Yes, those are good reasons. Convenience, and immunity to disturbances caused by high currents (e.g. ground bounce) in conjunction with the asymmetrical TTL logic thresholds. Another minor reason could be the ease of diode-ORing active low signals. I don't see any reason to assume that...
  6. KrisBlueNZ

    LED driver without IC and Transformer

    Look inside a commercially manufactured LED lamp! That will answer that question.
  7. KrisBlueNZ

    LED driver without IC and Transformer

    OK Arshid. Now, the photograph?
  8. KrisBlueNZ

    LED driver without IC and Transformer

    Sorry, I meant to say the AC voltage across R2 and the DC voltage across R3.
  9. KrisBlueNZ

    LED driver without IC and Transformer

    Arshid, can you measure the AC voltage across R3 and the DC voltage across R4? Also, upload a photo of your circuit.
  10. KrisBlueNZ

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

    I think that inductor is too small. What information do you have on the core you used? Ferrite materials have widely varying permeability figures. 80 turns could produce anything from 10 µH to 100 mH depending on the characteristics of the core.
  11. KrisBlueNZ

    LED driver without IC and Transformer

    And your hovercraft is full of eels. Steve, WHAT have you been smoking? LOL
  12. KrisBlueNZ

    Chicken Coop Door Opener

    Where do you get that from? Reference please. No it isn't!
  13. KrisBlueNZ

    Chicken Coop Door Opener

    The delay doesn't delay the closing or opening of the door. Think about what happens in the evening. As it gets darker, the ADC voltage increases (assuming the LDR is at the bottom of the voltage divider, as I suggested). So the value you read from the ADC represents "darkness", if you like...
  14. KrisBlueNZ

    The whole reason I am here... :)

    Hmm. That's a funny looking design. There's no transformer. It must have a non-isolated (half-live) output. It's likely that the switching device has failed. That's the three-legged thing mounted against the small vertical heatsink. Test for continuity, or measure resistance, between the middle...
  15. KrisBlueNZ

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

    No, the zener he left out is for regulation against input voltage variations. D3 is the output voltage regulation zener. But it's odd that the unloaded output voltage is 39V. With a 27V zener, the output voltage shouldn't go above about 32V. I think it would be a good idea to buy a known...
  16. KrisBlueNZ

    Chicken Coop Door Opener

    Yeah the schematic looks good. Re the pushbutton input being active low instead of active high, there's no technical reason for it. Doing it that way is slightly more common; the only reasons I can think of is having 0V on the pushbutton is a bit more convenient - you may be able to avoid an...
  17. KrisBlueNZ

    questionable RS-232

    It looks like there's some serious low-pass filtering occurring somewhere! Excessive cable capacitance maybe? Slew-rate-limited driver trying to transmit a high data rate?
  18. KrisBlueNZ

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

    That regulation is terrible! Can you capture some oscilloscope traces? The voltage at the right end of RS with no load and with load would be an interesting start.
  19. KrisBlueNZ

    The whole reason I am here... :)

    Assuming this is a switching converter, there's something else faulty in there. Usually it's the switching transistor or MOSFET - a 3-pin device on the heatsink towards the AC mains side of the board. Could also be the bridge rectifier - four-terminal device. Switching power supplies are...
  20. KrisBlueNZ

    What could be the failure cause of a circuit when it works 18 times over 20 times

    Psychic healing and "remote viewing" were not part of my education. How about posting a schematic and the definition of the logic in the ASIC so we have some idea where to start!
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