# Need Help In Combine 2 Voltage Source

Discussion in 'The Projects Forum' started by woon_h88, Sep 24, 2014.

1. ### woon_h88 Thread Starter Active Member

Mar 25, 2009
46
2
Hi,
I need some help in combine 2 voltage source in parallel to increase the current flowing in the circuit.

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R1 = R2=5 Ohm
R3=4.7kohm ( To let most of the current to flow to the USB
I used source conversion method and i should get around 2A at Node A..But when i tried it out its only give me around 33mA...When i removed 1 of the source, its still give me 33mA ..Is it my circuit is wrong?

Thank you..

2. ### wayneh Expert

Sep 9, 2010
12,406
3,256
Why use R3 at all?

Current is determined by the load, which you haven't specified.

3. ### Vinetou New Member

Sep 5, 2014
12
0
You need to know what is the resistance of your load in order to solve this circuit properly. Remember that you have two resistors in parallel in this circuit. One is the R3 and the other is your load. You really have 2A on node A. One part of this current will flow through R3 and the remaining part will flow through the load. To calculate how much current will flow through each one, you must determine the resistance of your load.

4. ### MrChips Moderator

Oct 2, 2009
12,658
3,461
Why do you need any resistors, R1, R2 and R3?

Where is the 5V coming from?

What is the USB device?

5. ### woon_h88 Thread Starter Active Member

Mar 25, 2009
46
2
Hmm... My usb is something like mobile phone...it's resistance is less than 100 ohm...(ttested by using direct 5v to the phone and measured the current...my 5v is from other part of the circuit which providing a 5v dc from a 12v ac dynamo (with rectifier and voltage regulator)... Using 1 source is not enough to charge a phone.. So my group though of using 2 source..but now the problem is the 2 voltage source can't combine (parallel, cos we wan to increase the current but not the voltage.) the r3 is just to forced moat of the current to the load as the load resistance is lower...about why I use resistance... Cos I trying to change the source to current source so I can parallel it...

6. ### MrChips Moderator

Oct 2, 2009
12,658
3,461
What is the required current and voltage to charge your mobile phone?
What is the voltage and current output of each of your charger sources?

You can put two voltage sources in parallel. One source is going to run flat out and its output voltage will drop until the second source starts to assist.

7. ### woon_h88 Thread Starter Active Member

Mar 25, 2009
46
2
The requirements for voltage is 5v and the current need to be more than 1A.. But less than 2 A... And the voltage source is just 5v with 32 mA..

8. ### MrChips Moderator

Oct 2, 2009
12,658
3,461
Then you need a bigger dynamo.

9. ### woon_h88 Thread Starter Active Member

Mar 25, 2009
46
2
So there no way to combine 2 voltage source to make the currents bigger?

10. ### MrChips Moderator

Oct 2, 2009
12,658
3,461
If you put two 32mA sources in parallel you will get 64mA source.

11. ### woon_h88 Thread Starter Active Member

Mar 25, 2009
46
2
ya...i did tried but for some reason i still getting 32mA..which is very strange...

12. ### woon_h88 Thread Starter Active Member

Mar 25, 2009
46
2
Hi..
Sorry to revive a post as i still seeking a way to increase my output current...

http://diyaudioprojects.com/Technical/Current-Regulator/

Hmm..If i addition added a Current-Regulator to my 5V output voltage regulator with the R1 ( on my current regulator side) to 0.5 ohm..Will i get at the load with 5V 2.5A? Say that if my load is just 1 ohm..

Last edited: Oct 15, 2014
13. ### wayneh Expert

Sep 9, 2010
12,406
3,256
No, that would be 12.5W output from a 6W input. Not gonna happen. There can only be losses, not gains.

14. ### thodoris46 New Member

Jan 29, 2013
10
0
What you are trying to make is very simple, it is difficult to you because you are doing electronics without ever opening a book to read.
Learn the basics , then read some more.After that read you're posts to yourself...

15. ### woon_h88 Thread Starter Active Member

Mar 25, 2009
46
2
Hi,
I dont know what u r trying to say, but please dont try to put demoralized comment...Problem is im been capped to clean energy which is my dynamo motor..Its can give a constant 6V with regular cycling..

Thank you..

Thank for the answer...Will try find others way...