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  1. KrisBlueNZ

    xor gate only use diodes

    Hi palahasan and welcome to Electronics Point. I've moved this thread to the homework help forum. Please post homework questions there. Do you understand the basic principle behind the circuit above? Do you know how it produces a voltage across the output terminals only when the input...
  2. KrisBlueNZ

    Help identify a Diode -

    Those diodes on the left really don't look like they're damaged. They just look very dirty. There isn't much solder on them, but there isn't much on the others either. That's normal for SMT (surface-mount technology) assembly. You said that the two diodes on the left (D4 and the other one) read...
  3. KrisBlueNZ

    PIC16F877A With GSM Modem SIM900A

    You could try linking the end pin, marked RTS, on JP2, to the 0V/GND rail. That will assert the RTS signal on pin 7 of the 9-pin D-sub connector. But the modem may also expect active flow control on DTR, on pin 4 of the 9-pin D-sub connector. I found a schematic for that board (attached to this...
  4. KrisBlueNZ

    Pioneer H-R100 8 track player

    I get some hits Googling for H-R100 but they're Pioneer not Hitachi...
  5. KrisBlueNZ

    Help Identifying Component

    How did you measure it? You need to set your meter to resistance range - if it has several, choose the lowest one, usually the 200Ω range - and connect the probes across the component. The meter will then tell you the resistance. If it's a digital meter, it can give you several indications: An...
  6. KrisBlueNZ

    Help identify a Diode -

    Hi there and welcome to Electronic Point :-) Thanks for the good explanation. I don't see anything obviously wrong with those diodes; they just look very dirty. I think you should start by cleaning the muck off the board and posting another photo. Use a toothbrush then cotton swabs, with a...
  7. KrisBlueNZ

    PIC16F877A With GSM Modem SIM900A

    I just realised the most likely problem - flow control signals. The modem is probably expecting active flow control signals on the other pins of the connector. There may be an AT command that you can send from the PC to the modem to disable hardware flow control. Alternatively, you can force...
  8. KrisBlueNZ

    PIC16F877A With GSM Modem SIM900A

    Good work! Thanks for those responses. I can't check your stripboard circuit because the connections aren't visible, but you certainly seem to know what you're doing, and your schematic looks OK, so I'm going to assume you've probably built it up correctly. I think it would be a good idea to...
  9. KrisBlueNZ

    Stage Line 500W amp repair project

    OK, as well as fuses, you should get some fusible resistors that you can use instead of fuses during power-up and adjustment. I suggest around 33~47Ω fusible resistors rated at 1/2W or 1W. Here's a suitable one: http://www.digikey.com/product-detail/en/FRM50SJR-52-47R/47DVCT-ND/2813217 and...
  10. KrisBlueNZ

    I need to power my Halloween costume

    Hi there and welcome to Electronics Point :-) You could try connecting thirteen 9V PP3-type batteries in series, and connecting all the strings across them. It won't last very long - maybe an hour - but it will work and it will be portable. Yes I'm serious. If you do this, keep everything...
  11. KrisBlueNZ

    PIC16F877A With GSM Modem SIM900A

    Your circuit looks right. You may have made a wiring error. There are various checks you can make. Try these, in this order. Power up your PIC circuit, with the USB RS-232 device disconnected. Measure the voltage on pins 3 and 2 at the modem connector with the modem powered OFF, and again with...
  12. KrisBlueNZ

    Hello

    Hi there and welcome to Electronics Point :) It's good to have you aboard! Edit: How about "Resistance is futile but inductance is kinda cool"? Or "Resistance is futile but capacitance has potential"?
  13. KrisBlueNZ

    Problem faced in generating more i/o's through AVR

    Yes it can, but you can't modify it by accessing the PINx register. You need to use the PORTx register.
  14. KrisBlueNZ

    Large array of 5mm LEDs (555 timer,LED flasher)

    Hi again and sorry for the long delay. I have been reconsidering my advice on protecting circuits from the automotive electrical environment. I've discovered that automotive load dump is not a normal occurrence; it only happens if the battery becomes disconnected while the engine is running -...
  15. KrisBlueNZ

    Stage Line 500W amp repair project

    Let's hope you've just made some mistake in the reassembly, not blown all of the semiconductors in the output stage. Now do you want to do a proper, careful job as I suggested in post #9? This involves dismantling the heatsinks, measuring all of the semiconductors (on-board and off-board)...
  16. KrisBlueNZ

    Members location

    I agree with you Daniel - at least that entering a location should be encouraged, perhaps with a dialogue box that appears during new user registration if the user doesn't enter a location, to remind them of the good reasons for entering it - it tells us their mains voltage and frequency, and...
  17. KrisBlueNZ

    Dynex DX-L42-10A Intermittent Issues

    Cool.
  18. KrisBlueNZ

    Problem faced in generating more i/o's through AVR

    Why did you repost your question? Did you see my response in post #11?
  19. KrisBlueNZ

    Rain Sensor Status

    Yes... But forget ground. The AC voltage appears between Phase and Neutral. Ground happens to be connected to Neutral, but it is not used for anything other than safety. Because Neutral is grounded, it makes sense to use it as the reference point when you're describing the voltage on Phase...
  20. KrisBlueNZ

    Problem faced in generating more i/o's through AVR

    It looks like you're trying to control the I/O port pins by modifying the PINC register. This is a read-only register that yields the states of the port pins. Writing to it has no effect. You should be manipulating PORTC instead.
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