[SOLVED] 16f877a power on problem

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You can only able to increase the output voltage by this method and normally the output will be 5.01 or 5.03V some thing likes that and you are only increasing it... so once look at the output voltage and what are the other devices connected in the circuuit?.
 


i have adjusted the supply to exactly 5V , the circuit includes opamp, controller and 3 digit 7 segment......
what should be done............
 

are you new to 877a or you ever bfr programmed this chip and worked fine for you? If you are a newbie check the programming procedure and configurations bits very well bcs everybody facing the problem in it.
else
what is the series resistor value of 7 segment and your power source ability...
 

cheetha said:
yes i am varying output voltage as output of most 7805 is not exactly 5V so to adjust it to 5V i have used this circuit ...
Click to expand...


Output voltage tolerance :

Fairchild LM7805CT 1A is 4% (0,2V) @ -40°C to +125°C
Fairchild LM7805ACT 1A is 2% (0,1V) @ 0°C to +125°C
https://www.fairchildsemi.com/ds/LM/LM7805.pdf

It will be very interested to see output voltage on different (usually higher) temperatures.

Is there is some special reason for 5,00V ?



Best regards,
Peter

:wink:
 


I am sure i have set the config bits correctly
i have used 330ohm resistors in series

Is there is some special reason for 5,00V ?
Click to expand...

it is necessary for accuracy of ADC measurement

????any suggestions
 

cheetha said:
it is necessary for accuracy of ADC measurement

????any suggestions
Click to expand...


You didnt mention that before, in thread question you mention only power problem or maybe you mentioned that but I missed.


Using Fixed Voltage Reference (FVR) for A/D conversion in enhanced mid-range PIC microcontrollers
https://embedded-lab.com/blog/?p=3045


A stable reference voltage is required in A/D conversion systems for accurate and repeatable data conversion. While this can be achieved externally by using precision voltage regulators or zener diodes, the enhanced mid-range 8-bit PIC microcontrollers facilitate this feature internally through the FVR module, thus avoiding the use of any external components. The use of internal FVR module also frees the external Vref pin, which means an extra GPIO pin. The microcontroller’s power supply voltage (typically +5V) itself can be used as the reference voltage for A/D conversion. While this allows the maximum range for A/D conversion, it could possible introduce errors in the conversion if the supply voltage is not stable (usually the supply voltage drifts with load conditions). Besides, if the range of the analog signal is much lesser than the supply voltage, it is always good to use a lower reference voltage for achieving higher resolution. The FVR module inside the 8-bit PIC microcontrollers of the enhanced mid-range family provides three stable and configurable reference voltages internally, which makes the design of data conversion systems more flexible and easier.


But you use PIC16F877...


Best regards,
Peter

;-)
 
Using Fixed Voltage Reference (FVR) for A/D conversion in enhanced mid-range PIC microcontrollers
Click to expand...

your post is very useful but
what if i want same functionality in 16f877a
and my problem is still not solveddd!!!!
 

cheetha said:
I am sure i have set the config bits correctly
Click to expand...
And you are absolutely 100% sure that LVP is disabled?

You say that you have set configuration bits correctly, but you don't say what you have set them to.
 

You say that you have set configuration bits correctly, but you don't say what you have set them to.
Click to expand...

HERE is attached config bits in genius programmer G540

**broken link removed**

Are you using transformer (6-0-6) ???
Click to expand...

i am using transformer of 0-12V before rectifier

plz help
 

Is that reset happens every your program or only your project program in this board?? try to implement a LED on off program in the same board and check its resets or not..
 

Is that reset happens every your program or only your project program in this board?? try to implement a LED on off program in the same board and check its resets or not.
Click to expand...

yes the led program is working correctly...
 

then now you know its your program.... You may post your code and schematic and somebody will help..........
Click to expand...

well i hunting the real cause of this problem..... except the config bit what could be the possible reason for it..?
 

cheetha said:
well i hunting the real cause of this problem..... except the config bit what could be the possible reason for it..?
Click to expand...
Well it is starting to look like a problem with your code and/or your hardware.

Post your code and your schematic and I am sure that forum members will find your errors in no time.

Not sure your config bits are right though - should DEBUG bit be on?
 

Well it is starting to look like a problem with your code and/or your hardware.
Click to expand...

what could be causing problem in coding and hardware includes power supply...
 

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