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  1. HellasTechn

    Serial communication problem.

    I will breadboard the circuit and let you know. Boy i have such a tiny knowledge on electronics that i dont even understand how the transistor works. I am not able to understand the circuit alone. i wonder how i could change that ? for example i have read about transistors that explain how they...
  2. HellasTechn

    Tank water level sensor.

    I know but it is their price that is keeping me off !
  3. HellasTechn

    Tank water level sensor.

    the depth is about 1 meter. The reed sw will have the same moisture problem as the ultrasonic sensor. The problem is that there is very little space inside the tank so installing a float switch does not strike me as the easyest thing to do. I think a simple pressure sensor is the easyest way to...
  4. HellasTechn

    Tank water level sensor.

    float switch can do the job, a pressure sensor is not a bad idea. Do they give analog signal based on measured pressure at the bottom of the tank ? could you suggest me one ? the tank holds about 250 US gallons (1000 liters of water.) About the ultrasonic , i am not sure.
  5. HellasTechn

    Tank water level sensor.

    Hello friends ! Here i am today, thinking about my new project which is a water level sensor for a tank. I think it would not be that hard to write a code on a picaxe for such project but what sensor should i use ? On the web i have seen ultrasonic sensors for arduino used as water level...
  6. HellasTechn

    Serial communication problem.

    It's just that from e-bay i bought 10 for 3-4 USD while from mouser for example 10pcs cost almost 50 USD...
  7. HellasTechn

    Serial communication problem.

    Yes. Again some chips gave me the same while other did not. Ebay/China. I have placed a new order for Maxim MAX3232EPE+ from mouser.
  8. HellasTechn

    Serial communication problem.

    Here are the scope images. 1. The RS232 source without anything connected on it. 2.The RS232 source connected on the max chip with power on. 3.The RS232 line connected on the input of the powered on max chip but with RS232 source disconnected. 4. The RS232 source connected on the of the powered...
  9. HellasTechn

    Serial communication problem.

    The lenght if the lines would not exceed 5-6 inches. the GND is as shown in the pic below. Scopings are on the way !
  10. HellasTechn

    Serial communication problem.

    I actually have both MAX232 and MAX3232EPE chips. The one i use is a MAX3232EPE... As far as i remember the only difference they have is that the max3232epe do not have internal 400K pullup resistors on TTL inputs. Hmmm i will try to switch the 3232 with a 232 chip to see what happens. I doubt...
  11. HellasTechn

    Serial communication problem.

    Dear dorke generally speaking, you are right but i disagree with your opinion about leaving unused inputs "floating". here i explain in more detail: Well on my project i use two wire communication (TX and GND from source RX and GND to receivers) but the block diagram you made is correct. You...
  12. HellasTechn

    Help designing a 5V UPS circuit.

    I see... You have a point there. I am not sure about the diode method though but its not a bad idea. any other suggestion ? maybe use of other battery ? There are many, cheap 18650 or 14500 batteries that i could use in series but again how could i charge them ? Are there chargers that can...
  13. HellasTechn

    Help designing a 5V UPS circuit.

    Hello Friends. Here is my idea: i have a circuit that runs on 5Vdc and a 12V supply with an 7805Vreg feeding it. My idea is to make a "ups" with a 9V Nimh (200ma rechargeable) battery so that when the 12V are gone the circuit will be running from the 9V battery again through the 7805Vreg. My...
  14. HellasTechn

    Serial communication problem.

    Well... Im not sure what a tri-state buffer is... I dont think a "switch chip" is what i need because i need it to keep the RS323 input hooked on the PC when there is no DC voltage present. I guess a buffer would be the way to go since it would isolate the rs232 input from the max chip thus...
  15. HellasTechn

    Serial communication problem.

    Thats right... The systems i have seen so far only use TX,RX and GND pins :)
  16. HellasTechn

    Serial communication problem.

    The way i see it is that the RS232 is a fairly simple protocol. In my case though the way the rest of the system is designd(not by me), it can accept nothing else but RS232 and RS422. The RS232 suits my needs better. In other words, i had no option about the comm protocol :) .
  17. HellasTechn

    Serial communication problem.

    True, i have seen that ! I tried that and did not help.
  18. HellasTechn

    YAMAHA AST-C10 no audio

    The problem lies right there ! Thako you so much Harald.
  19. HellasTechn

    GPS NMEA, Failover Circuit upgrade attempt.

    Now this is what i have noticed about theese fusess.... THey do not break the circuit in case of over current but they tend to keep current at the same level... Example i short my psu through a 50ma fuse at 2 volts and it restricts current to 50ma when i turn voltage up it keeps current at 50ma...
  20. HellasTechn

    Serial communication problem.

    Can you suggest me such chip ?
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