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[SOLVED] problem with my project

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darrenbkl

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Hi all,I m doing a simple project which need a supply of 5V.
So I use a 10v dc supply and a voltage divider to obtain a 5v output.
without connect to my project,my DMM show the unloaded output is exactly 5v.
but when i connect to the project, the DMM show it is around 1.92v.
why is it like tis?
 

laktronics

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Hi,
This is due to the voltage drop in your divider network. Use a voltage regulator like LM7805.

Regards,
Laktronics
 

daviddlc

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If your load is static (constant current) you can use a voltage divider, if your load is dynamic (changing current) the you need to use a Zener or voltage regulator.
 

lordsathish

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The problem also could be because there might have been some shorts in your
circuit. If there is a short between Vcc and Gnd in your circuit this might happen...
 

siongboon

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You cannot use voltage divider.
You should use a regulator to regulator the 5V output.

Your load will consume the current.
You can imagine that your load is a ohm too.
With ohm load parallel to each other,
you will certainly get a voltage less than what you have
before the load is connected.

Try LM7805 or LM2575.
**broken link removed**

Best Regards,
Siong Boon
 

lsimeon

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yes, siong boon is right, you should not do a voltage divider network to have your desired output voltage because if you will connect your load across the output terminal this will cause the two resistances to be parallel and resulting the total resistance to be lower than the resistance that you used in the voltage divider network which will then the voltage will decrease(following the ohms law)... that's the reason why when you measured your output when no load it is 5V but when you connected your load it decreases...

Added after 2 minutes:

you may use voltage regulators... the simplest way is to use zener diode...
 

manish12

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loading effect , if you still want to use the same ckt then use buffer op-amp.

but it is recommended that use regulators when std +5v is needed.
 

daviddlc

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Again, if your load is static, meaning it will consume the same amount of current all the time, you can use a voltage divider, just need to make the right calculation.

If your load is dynamic, meaning the current is changing with the time, then use a voltage regulator
 

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