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How do i power this circuit? Answered

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I want to control 4 dc motors with my old laptop's parallel port, via L293D motor driver chips and 7805 voltage regulators. my question is how to set it up to run it all on one power source(batteries)? the schematic im going to use is here. i want to change the 7812 to something that will put out 3v, any suggestions?

also, what batteries would be best to use, considering the 2 voltages it'll be running off(5v & 3v)?

i have included the pinout diagram for the L293D

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rickharrisBest Answer (author)2011-02-24

The L293 will drop about 1.7 volts so input 5 volts and you will get about 3 volts t the outputs.

Simple connect a 4.5 volt battery supply (3 cells) to pins 16 AND 8

motors to pins 14, 3, 11 and 6

HOWEVER be aware that the L293 is current limited to about 1.2 Amps - A lot of even small motors will draw this easily under load. IF it current limits it will shut down and you will think it's not working.

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thealeks (author)rickharris2011-02-24

so i can use just the 7805, and drop the other voltage regulator?

can i use the same power source for both L293D's? or should i seperate it?

thanks!

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rickharris (author)thealeks2011-02-25

Provided your regulator can supply the required current you can use the same source for them all just parallel it up.

Remember the L293 WILL current limit at fairly low levels.

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thealeks (author)rickharris2011-02-25

ok great thanks! i appreciate all your help

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thealeks (author)thealeks2011-02-24

also, can i use the output from the 7805 to power the IC and drive the motors? or do i need more than 1 7805?

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rickharris (author)2011-02-26

Depends on the current requirements of your motors AND the ability of the 7805 to supply that current - look at the data sheet.

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steveastrouk (author)2011-02-24

You need to define WHAT current your motors will run on, to decide whether a 7805 will hack it for you.

Steve

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thealeks (author)steveastrouk2011-02-24

the motors i want to use are here:
http://www.radioshack.com/product/index.jsp?productId=2102828

im not sure what current best suits them as the page makes no mention of current, only that they run on 1.5-3v, except one review states that under load the motor can draw up to 1.5A

the 7805 puts out ~5v at 1A.

is that going to be a problem? i havent purchased the 7805s(orv any other parts) so its not too late to make changes

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steveastrouk (author)thealeks2011-02-25

he 7805 limits at 1A it may be enough

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