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### Topic: Voltage Divider (Read 4270 times)previous topic - next topic

#### SagarDev

##### Sep 12, 2015, 02:20 am
I have made a voltage divider with 470 O at 9V VCC and 620 O at GND. Will it reduce current and if yes by how much?
Shakespeare's pen is an Electronics Engineer's Soldering Iron...

#### DrAzzy

#1
##### Sep 12, 2015, 02:32 am
Your question doesn't really make sense... What are you doing?
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#### weedpharma

#2
##### Sep 12, 2015, 02:44 am
I think he wants to know how much current is available if he has a voltage divider across a 9v battery. This may be to get 5v from 9v. If OP wants to use this to power an Arduino, then it is not how to do it. The divider will waste a lot of power. Use a V regulator.

Weedpharma

#### Wawa

#3
##### Sep 12, 2015, 03:00 am
I assume you want to measure battery voltage with your Arduino.
470ohm to battery and 620ohm to ground gives 5.12volt on the pin with a 9volt battery.
A bit too high with a fresh 9volt battery.
Problem is also that those low values drain the battery too much (9/1090 = 8.25mA).
Better to use e.g. 2x 10k.
That will give half of the battery voltage on the pin, and drains the battery with only 450uA.
Leo..

#### SagarDev

#4
##### Sep 12, 2015, 04:10 pm
Do voltage regulators reduce current?
Shakespeare's pen is an Electronics Engineer's Soldering Iron...

#### aarg

#5
##### Sep 12, 2015, 04:31 pm
Do voltage regulators reduce current?
No. For that you would need a current regulator.
... with a transistor and a large sum of money to spend ...
Please don't PM me with technical questions. Post them in the forum.

#### Wawa

#6
##### Sep 12, 2015, 11:37 pm
Do voltage regulators reduce current?
ONE resistor could reduce current.
It is frequently used to limit the current through a LED.

But if you want proper advice, it is better to tell us what you want to do.
Leo..

#### weedpharma

#7
##### Sep 13, 2015, 05:44 am
Do voltage regulators reduce current?
Possibly. Depends on the source and output.

If you have a fully charged car battery and use a 7805 to drop the voltage you also drop the current available from hundreds of amps to one amp.

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#### SagarDev

#8
##### Sep 13, 2015, 05:55 am
As Wawa said I want to measure battery voltage and current produced from the battery.
Shakespeare's pen is an Electronics Engineer's Soldering Iron...

#### runaway_pancake

#9
##### Sep 13, 2015, 06:17 am
I have made a voltage divider with 470 O at 9V VCC and 620 O at GND. Will it reduce current and if yes by how much?
I = Vcc / (470 + 620)
I = Vcc / 1090
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!

#### weedpharma

#10
##### Sep 13, 2015, 06:17 am
What battery? Size? Capacity? Expected current?

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#### Paul__B

#11
##### Sep 13, 2015, 04:02 pm
Come on guys!

I think we can deduce that the OP has calculated the ratio to drop 9V from a battery to the less-than-5V that is permissible to feed to the Arduino analog input.  He now adds that he wants to monitor the current draw also.

Well, perhaps we can offer him a means to measure current draw, though in fact that is much more complex.

We need to point out that while he got the ratio correct, a 1090 Ohm voltage divider will continuously draw some 8 mA from a 9V battery  - which would for example be a very bad idea if he was sufficiently misinformed to ever think of using this.

Clearly, the actual resistances need to be much higher, and even then if it is intended to turn the equipment off, the voltage divider must be disconnected also.

#### MarkT

#12
##### Sep 13, 2015, 04:25 pm
As Wawa said I want to measure battery voltage and current produced from the battery.
You use a multimeter for that.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### Wawa

#13
##### Sep 14, 2015, 01:21 am
This measures current and voltage with 12-bit accuracy.
Leo..

#### aarg

#14
##### Sep 14, 2015, 01:05 pm
As Wawa said I want to measure battery voltage and current produced from the battery.