Actually, it *is* working (but probably not as you desire). Electrical
current is indeed flowing from the battery, through the joystick pot, to
the motor. And, whenever you move the joystick, the pot will, in fact,
regulate the amount of current flowing to the motor. That meets most of
your design goals :-)
Unfortunately, the 5K ohm pot (typical) in the joystick is also
"limiting" the total current possible (based on Ohm's Law) to about 1
milliamp (assuming the battery is at about 5V). Nowadays, folks love to
talk about devices that only need such a small current to perform useful
work, but, alas, your motor is not that efficient. So, you're just
sending that small current into the motor windings, were it is getting
converted to a small amount of heat as the magnetic field generated by
the electrons running through the motor winding pushes (hopelessly)
against the motor's stationary magnetic field.
So, the circuit is working ... just not doing any useful work (unless
you really just wanted to drain the battery slowly).
As Mr. Tyng suggested, replacing the fixed resistor by a switch (0 or
infinite resistor) will probably get you closer to what you want to do,
as shown in various forms here:
http://www.rctankcombat.com/articles/speed-control/
Frank "Ain't Electronics Fun" P.
On 3/12/2012 12:54 PM, Neil Rochford wrote:
Can anyone tell me why this very simple circuit wont work ?
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