Simple Dual Motor Speed and Direction Controller Circuit for Telescope (5-11V Range)

Hi. I'm beginner and I would kindly ask you if you can recommend me some simple easy to build circuit or even kit with already built PCB for controlling rotation speed and direction for two motors simultaneously (both motors can be controlled independently at same time) . Motors are used for horizontal and vertical rotation of telescope for home use.

What controls I think that my circuit needs:
-2 potentiometers for fine,smoth controlling rotation speed for each motor
-2 start/stop buttons - each button is for starting and stopping corresponding motor
-2 buttons for motor rotation; one for each motor for choosing the direction of rotation

- probably few calibration resistors for calibrating voltage output range for each motors are needed.
From experiment, most used or operational range seems to be in around 5-11 volts and maybe it's not a bad idea to fix output range of controller in this range. Below 5V motor doesn't rotate (dead range?) and above 11V seems to be too fast for application, so putting full scale of potentiometer in 5-11 V may have it's benefits.

-maybe something else I missed?I need your suggestion since I have not experience here.

Motors are different, but they should have same nominated voltage (12V) and same maximal (motor-blocked) current (5A).

thank you

I would say that you would use an L298 Chip to drive the motors, It will drive both of them coupled with a heatsink. The potentiometer control is actually quite simple, Have an arduino read the analog value use inbuilt map function to map the ADC value from 0-1024 to 0-255 pass this value to the analogueWrite() function on two output pins of the arduino,
This will go to the enable pin of L298 . The inputs of the L298 will be connected to the arduino also. The arduino will read the states of the switches ( use a pull up resistor ) and set the values of the input of L298 required to move the motor in required direction ( refer to the truth table in L298 datasheet).

Do you mind using a micro controller? An Arduino, a couple of MOSFETS, and two pots would do this nicely. PWM would give you much finer control than just varying the voltage.

...and if those pots were in a joystick, all the better. I think you would find a joystick easier to use when controlling the motors -- more intuitive and both pots can be turned with one gesture..

Hi there John,
Just a few ideas to help:

Motors: make them big enough to handle the load easily, providing smooth motion.

Gearbox: a worm drive will be necessary for smooth steady tracking (particularly if you are into astronomy), suitable gearboxes ready-built or in kits are available from model shops etc.

Motor Speed Control: use a PWM speed control circuit, which provides better torque (rotary force) at lower motor speeds. (This will let your motors run smoothly and controllably at lower speeds.)

Have your telescope supported and pivoted each way from its centre of gravity. This will allow it to move freely with minimum force from the motors.

Astronomy websites will probably have useful plans and circuit ideas that will suit your project.

See also:
http://en.wikipedia.org/wiki/H_bridge
http://en.wikipedia.org/wiki/Motor_controller