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Power Supply Variation

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Suraj143

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Hi I want to power this circuit from a vehicle battery.

Can anybody tell whether it is ok or not?

What about the zenner diode?Is it ok?

Thanks
 

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Hi I want to power this circuit from a vehicle battery.

Can anybody tell whether it is ok or not?

What about the zenner diode?Is it ok?

Thanks

Off a 12V battery, no. Is there a junction at the 1N4007 and the zener? You would over-drive the zener with 12V applied. Why do you even need the zener? You can omit the zener and add another 1N4007 in series to lower your drop-out voltage of your 7805 even more. What are the circles on the collector of the transistor?
 
Hi rezer thanks for your reply.

Ya there is a junction at the 1N4007 and the zener.

I applied the zenner because I'm scared if the battery gives more voltage than the regulator input (30V).
Also if the battery voltage varies the brightness of the LEDs vary.So if I add a zenner it will be stable.

Can I ignore the zenner? & I like to place only one IN4007 not two diodes.

That circles are LEDs.

So any suggessions?
 
A vehicel battery should not give you more than 14.4 Volt

what you might do is first use a 7810 for a stable 10Volt and much more power handeling than a zener, from there go further down to a 7805

Robert-Jan
 
Hi rezer thanks for your reply.

Ya there is a junction at the 1N4007 and the zener.

I applied the zenner because I'm scared if the battery gives more voltage than the regulator input (30V).
Also if the battery voltage varies the brightness of the LEDs vary.So if I add a zenner it will be stable.

Can I ignore the zenner? & I like to place only one IN4007 not two diodes.

That circles are LEDs.

So any suggessions?

Your 12V system in your car won't get up to 30V, 14.5 maybe. Put a 10uF cap on the output of your regulator and mount your .1uf cap as close to the µC power pin as possible. The 12V system should not vary that much that it would be noticable with your LEDs. But if it is, maybe you can power the transistor circuit from your 7805. The output will be stable regardless of what the battery is doing. You might want to consider using another 1N4007 in series. You could even use a 9V regulator to step the voltage down to the 5V reg. Your regulator will get a little warm with 8V dropped across it.
 
A vehicel battery should not give you more than 14.4 Volt

Wow thats nice.

what you might do is first use a 7810 for a stable 10Volt and much more power handeling than a zener, from there go further down to a 7805

Oh no I cannot use two regulators.I need to be the design compact.

Without the zenner it will come the battery voltage directly to the LEDs via the resistor.That method is ok but due to battery level it can vary the brightness.

Thats the problem.
 
why not using 2 regulators

How much mili amp is your procesor using if it is less than 100 mA than use a 78L05 (small version)

still very compact

Robert-Jan
 
Your 12V system in your car won't get up to 30V, 14.5 maybe. Put a 10uF cap on the output of your regulator and mount your .1uf cap as close to the µC power pin as possible. The 12V system should not vary that much that it would be noticable with your LEDs. But if it is, maybe you can power the transistor circuit from your 7805. The output will be stable regardless of what the battery is doing. You might want to consider using another 1N4007 in series. You could even use a 9V regulator to step the voltage down to the 5V reg. Your regulator will get a little warm with 8V dropped across it.

Hi thanks for your input.Is this ok?
 

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extualy if you feed it from a car battery you don't need a 1N4007

it works only as a polarity protection but it will stabilize nothing as that yo have already DC voltages also the capacitor is not needed this big in my opinion

use a smaller one if you want to build it compact

Robert-Jan
 
extualy if you feed it from a car battery you don't need a 1N4007

it works only as a polarity protection but it will stabilize nothing as that yo have already DC voltages also the capacitor is not needed this big in my opinion

use a smaller one if you want to build it compact

Robert-Jan

Connecting any CMOS-circuit to the regulator output they will fry within no time. Spikes on the alternator DC have to be filtered thoroughly. So using some extra diodes in series with the regulator input pin might not be the worst idea. Instead the OP might use overvoltage protection diodes which are available for many different voltages. Every voltage beyond their rated input voltage will be shorted to ground respectively to +V. (Although they are pretty small from the package they can "digest" spikes with a total peak power of 600W.

Hans
 
Instead the OP might use overvoltage protection diodes which are available for many different voltages. Every voltage beyond their rated input voltage will be shorted to ground respectively to +V. (Although they are pretty small from the package they can "digest" spikes with a total peak power of 600W.
Hans

Hi thanks for your comments.Can you tell me how to add overvoltage protection diodes?

What are the suggestions I have to do in my last schematic.
 
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Connecting any CMOS-circuit to the regulator output they will fry within no time. Spikes on the alternator DC have to be filtered thoroughly. So using some extra diodes in series with the regulator input pin might not be the worst idea. Instead the OP might use overvoltage protection diodes which are available for many different voltages. Every voltage beyond their rated input voltage will be shorted to ground respectively to +V. (Although they are pretty small from the package they can "digest" spikes with a total peak power of 600W.

Hans

I agree with you but I was not in the impression that the circuit whas build in a car conected to the alternator circuit but only on a battery

still if you use a 7810 that should smoothen the voltage so that it would not be a problem if it would be conected in a vehicel

Robert-Jan
 
Ok this is the circuit I'm going to use.Is it ok?

Hard to find some special components like LDO regulators & some inductors.
 

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If you apply 12v to the anode of the 1N4007 very high current will flow briefly into the 1000 µF cap, probably damaging the diode.
Use a small series resistor; it also helps make the cap into a low pass filter, because a cap across an ideal voltage source with no upstream impedance doesn't do anything except take up space.
 
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