problem with 7805 - Electronic Circuits Projects Diagrams Free

mnoman · 7th November 2006, 09:48 PM

I am using 7805 with the 89c51 to transfer data serially to PC the problem is that while the power is ON no data is displayed on the PC as soon as the I switch of the power a burst of DATA is displayed OR if the switch is made to ON and OFF several times then it becomes OK and start sending data continiously. I think that it is the problem with 7805 as I had connected Two 7805 with the single supply one for 89c51 and other for some other circuits
can any one know how to solve the problem.

tunedwolf · 7th November 2006, 10:09 PM

I'm not quite sure what you mean about the two 7805's...if you mean they are both connected to ground at the same point and both connected to your unregulated power supply, then that's ok...but if you have one of them connected to the unregulated power supply...and the other connected to the output of the first one, then the second regulator won't work properly because it's input voltage will be too low. Also make sure you have enough decoupling on the input and output of each regulator, otherwise satbility problems will arise...
The PC not receiving the characters, or more likely not displaying them, is probably down to a software problem. Check your data tx line on your board to see if it is or isn't sending when you expect it to.

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7th November 2006, 09:48 PM	(permalink)
mnoman	problem with 7805 I am using 7805 with the 89c51 to transfer data serially to PC the problem is that while the power is ON no data is displayed on the PC as soon as the I switch of the power a burst of DATA is displayed OR if the switch is made to ON and OFF several times then it becomes OK and start sending data continiously. I think that it is the problem with 7805 as I had connected Two 7805 with the single supply one for 89c51 and other for some other circuits can any one know how to solve the problem.

7th November 2006, 10:09 PM	(permalink)
tunedwolf	I'm not quite sure what you mean about the two 7805's...if you mean they are both connected to ground at the same point and both connected to your unregulated power supply, then that's ok...but if you have one of them connected to the unregulated power supply...and the other connected to the output of the first one, then the second regulator won't work properly because it's input voltage will be too low. Also make sure you have enough decoupling on the input and output of each regulator, otherwise satbility problems will arise... The PC not receiving the characters, or more likely not displaying them, is probably down to a software problem. Check your data tx line on your board to see if it is or isn't sending when you expect it to.