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  1. HellasTechn

    Disable backlight of LCD monitor

    That is exactly what he did. he is using the LCD without its case or the reflectors on its back. Removing the LED backlight should not affect the LCD display. In other words picture should be displayed on the LCD no matter if the backlight is connected or not. Ofcource you could always leave...
  2. HellasTechn

    Have I bricked my Arduino Uno? Problems with uploading to board

    Hello. It would be much better to provide more information about the version of your board, your project and what exactly you did before you realize that the Micro controller is "bricked". I am not familiar with Arduino but i do know about Picaxe. It is not the same but might have similar...
  3. HellasTechn

    Regulator question.

    Tag (metal back of the regulator) is always connected to the center pin. for the 78xx series is ground and for the 79xx series is input.
  4. HellasTechn

    Regulator question.

    Yes that i fully understand besides current does not really have polarity, it is just movement of electrons. What defines polarity is the direction of the electrons movement.
  5. HellasTechn

    Regulator question.

    Yes i meant the negative lead. My mistake. I was testing an 7915 regulator.
  6. HellasTechn

    Regulator question.

    No theese are genuine. i just bought a new one and checks out ok the way i mentioned in post 1. I guess that answers my question about the parts being bad. It is true though that capacitors are required when used on circuit. Thank you Audioguru !
  7. HellasTechn

    Regulator question.

    Hello ! I have a few 78xx and & 79xx Vregulators. I suspect some of them are bad. The 78xx i test with my DMM and bench psu by connection the positive of the PSU to pin 1 , the negative to pin 2 and read output with my DMM from pin 2 to pin 3. I have an 7915 Vreg that i connect as follows ...
  8. HellasTechn

    USB to UART serial converter.

    No... i also had output scopings.
  9. HellasTechn

    Serial communication problem.

    You are correct sir ! its a hardware rs-232 serial port.
  10. HellasTechn

    Serial communication problem.

    Could you please take a look at my post #27 ? so my scopings of the max232 output should not be +4V at idle state but actually +5V...
  11. HellasTechn

    Serial communication problem.

    That's what i was planning to do anyway. Yes, your help is highly appreciated! I unfortunately i have difficulties understanding the math. Ho well, i am pretty sure i need to read the PDF files on post #39 throughly before we can continue this tutorial. P.S. Shouldn't we move it to a...
  12. HellasTechn

    Serial communication problem.

    I will work on it... I am going to breadboard the circuit with a 2n2222 that i have. For Vcc i will use a 9V battery and an 7805Vreg. For input signal i am going to use my bench psu so Vbe will be a dc voltage from my psu. forward bias would be negative of psu to emitter and positive to base and...
  13. HellasTechn

    Serial communication problem.

    Funny this topic started as communication problem and is ending as transistor tutorial. Maybe we should move theese posts to an other topic probably called Transistor lessons ? This is really very interesting and i thank you all for helping me out this way !
  14. HellasTechn

    Serial communication problem.

    I am not sure... if its large enough it should be off because BE will be reverse biased and output should be Vcc
  15. HellasTechn

    Serial communication problem.

    Why would that happen ? because of the transistor properties ? is it not driven directly to saturation and cutoff areas ? The way i see it in post #24 picture 1 the voltage range is from -9V to +9V RMS so i dont think i will have such problem. Why do i have to connect emitter to "gnd" and...
  16. HellasTechn

    Serial communication problem.

    True, only in my case the TTL board use active high signals (logic 1 = +5V). What if i use a PNP transistor to make an rs232 to ttl converter that will not invert the signal ? something like the diagram pictured below. My thinking is that when the rs232 signal will be positive it will be...
  17. HellasTechn

    Serial communication problem.

    It's clear to me that TTL has purely to do with voltage levels. The way a system preceives theese voltages is a different story. I will get back with a new diagram so you can all advice me further ! Its just that i am short on time theese days thats why its taking me long to write back. Thank...
  18. HellasTechn

    Serial communication problem.

    Correct. with open base there is no bias at all. Still the same outcome though. Yes. 5V logic 1 and 0V logic 0. I think i got it now. The circuit actually works as i thought but it's just that TTL signals are "active low" (logic 1=0V and logic 0=5V) so it's only natural that while VBE is >-3...
  19. HellasTechn

    Serial communication problem.

    I have tested the max3232 that i have on breadboard with 0.4uf caps and different test with 1uf caps (could not get 0.1 electrolytic) and i got the same 5V cd on the input of the rs232 but 0 volt on the output of ttl.
  20. HellasTechn

    Serial communication problem.

    Because BE junction is reverse biased. What i dont get now is this : ttl signal is idle 0V and high 5V the rs232 signal is >-3V (idle state), with the ec open the output will read 5volts and when rs323 pulses high >+3V then ec is closed affectively grounding vcc through the resistor so the...
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