A problem faced using L7805CV IC

thatoneguy

Joined Feb 19, 2009
6,359
Milwaukee sparks more in reverse and doesn't go full speed for me, cordless, same with makita corded, not talking a HUGE difference, maybe 100RPM or so for the corded, visibly slower with the cordless drill-driver.

They advance the brushes slightly for more torque in the forward direction.

All of this can be done with gears as well, with similar results, but the load on the motor would be the same.
 

Thread Starter

MerlinM1

Joined Dec 5, 2010
20
What is the motor you are using?

Can you measure the terminal voltage to see if it is the same in both directions?

Some brushed motors will run in reverse, but are optimized for forward movement, example would be cordless drills.
m using a 12 V CCW DC motor... i checked my own troubleshooting methods, and found that yes, the motor is the root of all this, why did this happen???.... i mean dont DC motors work well in both directions???.... it takes 300mA current during forward motion, and only 105mA in reverse motion, my purpose wont be solved this way... how abt using servo's/??... but i never worked wid servo's are they as easy to use as DC motors????
 

Thread Starter

MerlinM1

Joined Dec 5, 2010
20
I've always used the ACT version of the 7805, they're a bit beefier but as with any you need a heat sink unless the current draw is minimal:
http://www.mouser.com/Search/ProductDetail.aspx?R=LM7805ACTvirtualkey51210000virtualkey512-LM7805ACT
your idea seems fine, but well, after the grounding problem solved, my L7805CV doesnt get heated up... it remains cooler... the problem i was doing was i was unknowingly shortcircuiting its o/p terminals but now alls fine..
thnax..:cool:
 

thatoneguy

Joined Feb 19, 2009
6,359
m using a 12 V CCW DC motor... i checked my own troubleshooting methods, and found that yes, the motor is the root of all this, why did this happen???.... i mean dont DC motors work well in both directions???.... it takes 300mA current during forward motion, and only 105mA in reverse motion, my purpose wont be solved this way... how abt using servo's/??... but i never worked wid servo's are they as easy to use as DC motors????
It depends on the motor design. Most brushed motors are reversible (all Brushless are, but the circuitry is more complicated), but those that are advertised as "high torque" are usually better in one direction than in the other, as the commutator is set so the brushes give a bit of advance to the coil for highest torque.

If this is a low speed application, you can modify an RC Hobby Servo by taking it apart, removing the position encoder (usually a pot), and snipping off the limit peg on the topmost gear. Then connect red and black directly to the motor rather than through the small PCB inside. Reassemble it and give it power, ignoring the 3rd wire, and they will turn at low to medium speed with fairly high torque for their size.
 

Thread Starter

MerlinM1

Joined Dec 5, 2010
20
It depends on the motor design. Most brushed motors are reversible (all Brushless are, but the circuitry is more complicated), but those that are advertised as "high torque" are usually better in one direction than in the other, as the commutator is set so the brushes give a bit of advance to the coil for highest torque.

If this is a low speed application, you can modify an RC Hobby Servo by taking it apart, removing the position encoder (usually a pot), and snipping off the limit peg on the topmost gear. Then connect red and black directly to the motor rather than through the small PCB inside. Reassemble it and give it power, ignoring the 3rd wire, and they will turn at low to medium speed with fairly high torque for their size.
hmm.... sounds great, but why cant i get a DC motor fulfilling my task the same way???...
if i am buying the wrong thing, could u plz suggest what kinda motor shuld i ask for when i go to buy them???...
 

thatoneguy

Joined Feb 19, 2009
6,359
What is the use for the motor? Size needed? Budget?

Maxon are very good motors, but rather spendy. Cheaper "hobby motors" that are small and reversible are common, but the gears for them are harder to find.
 
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