# Amplifying power to motors

Discussion in 'General Electronics Chat' started by Wolfgang, Dec 29, 2014.

1. ### Wolfgang Thread Starter New Member

Dec 29, 2014
6
0
I have a 18 volt dc motor that is being supplied with 6 v or -6 volts. How would I amplify the 6v to 18 or in reverse -6 to -18 v using a 12 v battery as an additional power source.

2. ### blocco a spirale AAC Fanatic!

Jun 18, 2008
1,463
372
So, do you want to power an 18V motor from a 12V battery?

How much current does your motor require?

Jul 18, 2013
10,867
2,528
If using an additional 12v battery then just series them up for 18v?
Max.

4. ### Wolfgang Thread Starter New Member

Dec 29, 2014
6
0
6+ 12 v is 18 v. I can't put them in series because when the motor goes in reverse the ground and source swap so the it would be -6 + 12 v only 6 volts and it would be in the wrong direction. When forward I get 6 volts want 18. When in reverse I get -6 want -18.

5. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,066
Connect your 12V battery in-series with your existing 6V supply. Now you have 18V. Since it seems you need to reverse the motor, use an 18V H-Bridge, with the motor connected across the sides of the bridge. Your positive logic inputs (presumably 5V) can be referenced to 0V...

6. ### blocco a spirale AAC Fanatic!

Jun 18, 2008
1,463
372
If connected in series isn't there a risk, if the battery becomes discharged, of it receiving a reverse charge from the 6V power-supply?

7. ### Wolfgang Thread Starter New Member

Dec 29, 2014
6
0
The 6 v supply alternates to -6. Its like an ac supply, but there is no fixed frequency.

8. ### Wolfgang Thread Starter New Member

Dec 29, 2014
6
0
the 6 v supply used to power the motor hence the 6 and-6 volts for direction. Now I need more power so I have to increase the voltage to 18 for forward and -18 for backwards. The 6/-6 v supply isn't a battary it is the power coming from a seperate chip that I can't modify.

9. ### Alec_t AAC Fanatic!

Sep 17, 2013
5,980
1,138
Can't you just buy an 18V supply? Probably cheaper (certainly simpler) than building a circuit to combine and reverse the two supplies you have.

10. ### Wolfgang Thread Starter New Member

Dec 29, 2014
6
0
But how to swap the polarity of the 18 v battery so the motor can go in reverse? I can build and solder a circuit but Im clueless as to the design for this.

11. ### Alec_t AAC Fanatic!

Sep 17, 2013
5,980
1,138
As Mike said (post #5), use an 18V H-bridge.

12. ### tcmtech Well-Known Member

Nov 4, 2013
2,120
1,754
A simple DPDT relay would work just fine for the power handling and reversing process.

13. ### Wolfgang Thread Starter New Member

Dec 29, 2014
6
0
Thanks. Would it be possible to build a circuit like it using transistors instead?

Sep 17, 2013
5,980
1,138