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  1. gorgon

    Why is relay latching? :(

    I think I would have tried the big capacitor on the 5V supply, to make the supply stiffer. Both the bell and the buzzer draw a lot of current when starting, due to the magnetic build up. You don't say how often the bells are used over a week, but I suspect you get some sort of magnetic...
  2. gorgon

    Why is relay latching? :(

    nWhat exactly happens when the bell/buzzer stops working? Does the magnet pull the banger and holds it in, or does it not pull it enough to break the interrupter contact? Have you measured the 5V when it is working/ stops working? Is it still 5V or has it collapsed to a lower voltage? What is...
  3. gorgon

    Why is relay latching? :(

    You should add a diode on each relay coil to reduce the reverse peak voltage that may ruin the switches on the first relay, and make them stick. It may also be a good idea to add some sort of snubber circuit over the bell switch(es) if they are coil based. 47 ohms in series with 100nF should...
  4. gorgon

    refresh rate for dot matrix

    You should also include the clock speed you are running the pic on. A schematic would be the first step for us to see what you are working with, the next would be a listing of your code.
  5. gorgon

    refresh rate for dot matrix

    Why don't you explain what is completely wrong about this? I was answering the 8x8 matrix described in post #10, so this is not an answer for a 16x128 matrix. @OP Regarding the 16x128 matrix. this is a big matrx for a first time designer, and the requirement for the high speed SPI or serial...
  6. gorgon

    refresh rate for dot matrix

    The 'normal' lower limit for a frame rate is >50Hz, preferable higher. For a small matrix like 8x8 you may choose 100Hz. This mean that all diodes are scanned 100 times/ second. For a display of 8 lines by 8 columns, each column has 1/100*8 or 1.25ms of display time. This is not very fast and...
  7. gorgon

    ID Please

    Could it be a glass gas discharge device for overvoltage protection?
  8. gorgon

    Assembly statements

    PICs has never been a favorite for me, but I've made several projects using the smaller variants in my job. I've also used the Atmel AVR variants in some projects, and I prefer them to PICs. I suppose I may do more hobby related programming in the future, beeing made redundant, and having...
  9. gorgon

    Assembly statements

    Ok, that is a new angle. Just out of curiosity, how do you do that with a PIC? The only way I can see is using a sort of index variable resulting in a conditional goto after processing in the 'called routine'. I then suppose you use a normal goto to get there.
  10. gorgon

    Assembly statements

    Of course, but I was refering to the macro vs call discussion above. You can of course write all instructions every time, copy and paste, or whatever..
  11. gorgon

    Where can i buy this zener Diode or what is that?Please i need help

    If this zener is used in the backlight circuit, it may be interesting to know the type of display that is used. Have you got a part number on your display?
  12. gorgon

    "Has it got the Cobalt?" (story)

    When i started working as a young service engineer back in -75, the serious programmers in the company wrote all their cobol programs on punched card programming sheets by hand. Those were then transferred to punched cards by them, or a secretary, and read by the big IBM computers we had. Many...
  13. gorgon

    Assembly statements

    One thing to be aware of, working with the smaller PIC microcontrollers, are the sometimes very limited stack capacity. If you use nested calls, you will eventually most certainly cut off the limb you are sitting on, and not return to where you want. In these cases macros with code repeats has...
  14. gorgon

    Help with RS-232 connectivity

    You could use a 10lead(9) ribbon cable and a 9pin dsub with ribbon press connection. The other end of the ribbon cable can be pressed into a 10p female connector, or soldered to whatever you need to connect to. Another way to do it is to solder wires to a standard pitch header from the Dsub, and...
  15. gorgon

    questionable RS-232

    The reason for the rounding is a combination of capacitivity in the cable, a small resistance in the cable, and last but not least the 300 ohm serial resistance in the RS232 driver output. Together this will make a lowpass filtering effect on the signal, and the max frequency of the transmission...
  16. gorgon

    questionable RS-232

    For me it looks like this is a normal RS232 +/- 12V signal, with some cable RC included. From the pictures I would assume you are running 115200 baud, and that is speedy if you have som cable length involved. RS232 is defined with max cable length vs max speed, due to the design of the...
  17. gorgon

    Lead-Acid temperature compensation in charging

    Depending on the local ambient temperature it may be very important to have the temperature compensation installed correctly. When the ambient temperture is increasing, the nominal charge voltage is decreasing. Geting an over voltage charge over time, will increase the internal temperature ov...
  18. gorgon

    My MCU circuit can't start by itself

    The oscillator circuit in the PIC already has a parallel resistor inbuilt. Are you sure the capacitors are 22pF? For the 16MHz crystal, the rated capacitor range is 15-33pF. As said, you should use HS mode for this frequency. Try some different values of the load capacitors to try out. In the...
  19. gorgon

    Switch Type

    Looks like a set of conducting rubber switches. 2 steps each direction. The main question is how the pressure pads in the mechanical part is aligned.
  20. gorgon

    If the source voltage is the same as LED voltage, is a resistor necessary?

    Any LED will have a defined voltage range, not an exact voltage value. The 20 mA is only certain if you feed the LED 20mA, then you may have 3.6V over it. You can't do the reverse assumption. As said before the temperature is the main factor for what the Vf is at any moment. The 20mA in the...
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