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Recent content by hm_fa_da

  1. hm_fa_da

    Questions on C programming for STM32

    Hello, I have a question on C programming for STM32 by Keil compiler: If I define a variable on top of my code, (before main() ) like: /* USER CODE BEGIN PV */ uint8_t Var_x = 5; /* USER CODE END PV */ int main(void) { program code .... HAL_NVIC_SystemReset(); // **Software reset...
  2. hm_fa_da

    Strange problem using printf in C with STM32F407VE

    Thanks for your reply, as I wrote in my last post, I found the problem, In the last version of STMCubeMX (which I recently updated to) it doesn't check "Use MicroLIB" in the output project by default and it makes the problem, when I manually check it, code size decreases and works fine. I...
  3. hm_fa_da

    Strange problem using printf in C with STM32F407VE

    The printf function works well, the only problem is when I use it in code, startup problem occurs as I described. I just tried different settings in compiler and found when I check "Use MicroLIB" the startup problem doesn't occur ! and code size also decreases ... here is a screenshot: I...
  4. hm_fa_da

    Strange problem using printf in C with STM32F407VE

    Hello, I've used printf function in many of my older projects without any problem, i.e stm32f103 or stm32L071 MCUs and ... (all Keil compiler). but just got a strange problem running a simple code on STM32F407VET6. The problem is that when I program the code on the MCU, after restart, it...
  5. hm_fa_da

    Floating base pin of optocoupler output transistor ?

    Hello, I am going to use 4N26 vishay optocoupler for a project, it is a 6pin optocoupler as you see in this picture: the output of the optocoupler - (photo transistor) has 3pins, first I used a 10K resistor between B (pin6) and E (pin4) but didn't function well, means when I turned on the...
  6. hm_fa_da

    How to limit the maximum output power in this circuit ?

    Thanks for your reply, I was just looking for this formula "Po = (Vo/2)²/R" which you mentioned, so for 9V Vin, R would be 67.5 ohms. However, there is a point, the current when calculating maximum Po can't exceed Fuse Amperage, in the schematic i sent, considering 67.5ohms for R, the maximum...
  7. hm_fa_da

    How to limit the maximum output power in this circuit ?

    Thanks for your reply, I sent the corrected schematic here: Assume Vin is 9V (Zener was just a protection for higher voltages - so in my question it has no role) , The schematic input is in left side, output right side. I mean by MAX Po: I want to set a value for R so that any load connected...
  8. hm_fa_da

    How to limit the maximum output power in this circuit ?

    Hi, How do you calculate the minimum R value if you want to limit output power to i.e 0.3W ? assume Zener and Fuse work at their nominal values.
  9. hm_fa_da

    How to calculate Zener diode power according to intrinsically safe (ATEX) standard ?

    Thanks for your reply, In fact it's not matter of only science calculations here, i.e according to ATEX rules we should use at least 2 or 3 parallel zener diodes for ib and ia levels in which the power calculations should be passed on each of them alone. or according to the standard, for other...
  10. hm_fa_da

    How to calculate Zener diode power according to intrinsically safe (ATEX) standard ?

    Hi, I'm little confused by calculation method of a Zener diode power according to IEC60079-11 (intrinsically safe devices) ! To simplify my question, I just sent a sample schematic here : I know in how to calculate the power of the zener in normal conditions, but in ATEX world, many things...
  11. hm_fa_da

    Active Precision Current Limiting circuit needed

    Thank you all for replies, I need a constant Max 7.5V output with max 100mA Current limiter. I already have 7.5V constant voltage regulator. About what you guys suggested, FPF2700 is not good because the current limit starts from 0.4A and has tolerance of 20% ... AL5809 Can be good choice...
  12. hm_fa_da

    Active Precision Current Limiting circuit needed

    Thanks, Maximum input voltage is 7.5V. I currently found LT3092 , very suitable as respect of size and technical parameters but it's little expensive for mass production purposes. I'm still searching more to find a better choice ... - - - Updated - - - As precise as general active op-amp...
  13. hm_fa_da

    Active Precision Current Limiting circuit needed

    Hi all, I'm trying to design a precision active current limiter circuit to limit output current down to 100mA. I saw many different circuits in net, some made by BJT transistors which are not precision enough. I don't have much space on my PCB, so priority of the design is being simple and low...
  14. hm_fa_da

    Power Supply for M95 GSM module to be compatible with ATEX limitations.

    Thanks all for replies, Did you get a lab certification for your design ? As I know active current limiters are allowed but it should be used like double current limiter circuits for ib at least. the way you regulated the voltage by an LDO is not voltage guaranteed, maybe the circuit be IS, but...
  15. hm_fa_da

    Power Supply for M95 GSM module to be compatible with ATEX limitations.

    Thanks, There is nothing about IS considerations in the Module Datasheet, neither design note. In fact my question is that if i do not limit the current to the module to a value lower than 2.1A, then according to that certificate, the module would not be IS (intrinsically safe) ? If i have to...
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