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Motors not spinning in RC Car

TimeManx

May 11, 2010
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May 11, 2010
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Hi guys, I'm building a basic RC Car. There's an LED in the receiver circuit which lights up when I press a button on the remote. But when I connect the motors, it stops lighting and neither do the motors spin. It just spins on the first button press after connecting the batteries (the LED also blink dimly) and not after that.

Attached the schematic for the receiver section.

Thnx

EDIT: Corrected the schematic
 

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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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Are those KA7805's voltage regulators? If so, they appear to be connected incorrectly.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
25,510
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OK, It still looks wrong.

For a 7805, pin 1 is connected to +ve, Pin 3 is 5V output, and pin 2 is the common which must be connected to gnd (-ve in your case).

It is also convention to draw the +ve rail at the top of the diagram.

I'm also curious as to why you need two 5V regulators?
 

Resqueline

Jul 31, 2009
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The 7805's look right to me now (apart from conventions, and the 0.1pF cap) though I haven't checked the other IC pinouts & data.
It's usual to keep motor and receiver supplies separate in RC applications.
What's the main battery voltage/power? How much current does the motor draw? Do you have a multimeter?
 

TimeManx

May 11, 2010
31
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May 11, 2010
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currently im givin a 9V supply and using two 6V motors. but ive tried using 3V motors too with the same result.
 

Resqueline

Jul 31, 2009
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9V should be ok, but what kind of power is it capable of delivering? Also, motor voltage has (almost) nothing to do with the matter, it's the power draw that counts.

Start with measuring the 9V supply first, it shouldn't drop below 7.2V. Then measure the 5V supplies.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,510
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Yeah. Must be some weird caching thing. I'm still seeing the wrong (original?) diagram. I thought that the motor was running from the unregulated supply but it's just the catch diodes that are being returned to it.
 
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