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Regulated power supply

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emavil

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Hi,

Microcontroller circuits are powered by +5VDC regulated. I've seen lots of this in every microcontroller circuit especially L7805CT. I really wonder the role of capacitors in both sides of the regulator. Do these things have impact to the stability of the power supply? I read applications notes suggesting that an inductor or coil is also required. What is the proper way of constructing power supply circuits for microcontrollers. Especially for automotive applications where NOISE are very evident?
 

emavil said:
Hi,

Microcontroller circuits are powered by +5VDC regulated. I've seen lots of this in every microcontroller circuit especially L7805CT. I really wonder the role of capacitors in both sides of the regulator. Do these things have impact to the stability of the power supply? I read applications notes suggesting that an inductor or coil is also required. What is the proper way of constructing power supply circuits for microcontrollers. Especially for automotive applications where NOISE are very evident?
Click to expand...
Those capacitors are there to prevent oscillation of voltage regulator in case of long power supply lines/wires. They don't have any impact on voltage stability.
 

Well in automotive applications there is NOISE due to the ignition o the car and in these case and inductor or coil is needed, they are called chokes, you must use them in every electronic device conected to the car, for example autostereos.
 

CHECK THE DATASHEET OF 7805......TAT IS ENOUGH I THINK......ACTUALLY it all depends on current and power....if ur using a lot of current and the system has no power to sustain dat current then it oscillates....hence a large value of cap might reduce it...but not eliminate it.....so on an avg 1000µF cap is enough....
 

yah thanks, but i'm very much interested in the choke coil, could you please teach me the basic mathematics on how to compute the value for the coil e.q. the number of turns, the diameter of the wire, and the material to be used.

Can you give me also sample application circuit with choke coils?
 

why dont u try the SMPS power supply..the supply is nicer and constant compared to the regulated one...
 


qmriso said:
why dont u try the SMPS power supply..the supply is nicer and constant compared to the regulated one...
Click to expand...

??? What are you talking about...
 

Re: Regulated power supply - to find inductance

To find the value of inductance
1) In single layer coils ( wheeler's method )
L = (r² N² ) / [25(9r+10*l)]
where
L = inductance in micro henries;
r = radius of coil ( measured to the centre of the conductor) in milli metres;
N = number of turns;
l = the overall lenght of winding in millimetres

2) multi layer coils:
L = (N² /13.5) logbase10[4.9r/(1+c)]
 

Re: Regulated power supply - to find inductance

gamana said:
To find the value of inductance
1) In single layer coils ( wheeler's method )
L = (r² N² ) / [25(9r+10*l)]
where
L = inductance in micro henries;
r = radius of coil ( measured to the centre of the conductor) in milli metres;
N = number of turns;
l = the overall lenght of winding in millimetres

2) multi layer coils:
L = (N² /13.5) logbase10[4.9r/(1+c)]
Click to expand...


thanks gamana
 

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