1. DC motor principles Speed control Direction Stepper motor principles
Motor control
DC motor principles
Speed control
Direction
Stepper motor principles

2. Robot motor control options
All DC motors (with gearbox option)
Mix of DC and Stepper motors
All Stepper motors
DC Supply
Speed Control
Direction Control
Position Control
Motor

3. DC Motor Control Principles
A permanent magnet DC motor the field current If is constant but it still responds to both voltage and load current.
Apply a voltage and the motor will start running in one direction; reverse the polarity and the direction will be reversed.
The voltage V across a motor is the main factor that determines the motor’s running speed, and the current through its armature windings determines the torque.
Applying a load to the motor shaft, it will draw more current Iaand this will also afect the speed of the motor. The speed ω equation is:
ω= (V-IaRa)/KvIf

4. 1. Transistor (Base) Controller
One of the characteristics of a transistor being if the current flowing into the base is increased, the current flowing in the collector, and hence through the emitter leg is also increased.
The current flowing into the base is controlled by the adjustment of VR1.
VR1 also determines the voltage across the motor from 0v up to about 7.5 v (from a 9v supply) so the controlled speed range is 0% to 83%
Components
R1 = 100 ohm
VR1 = 4700 ohm
D1 = Diode (1N4001)
Transistor = (TIP 31A

5. DC Speed control with (555) Timers
Current only flows through the motor during the ON or ‘Mark’ portion of the Pulse Width Modulation (PWM) waveform.
If the frequency of the PWM input is high enough, the mechanical inertia of the motor cannot react to the ripple wave; instead, the motor behaves as if the current were the DC average of the ripple wave.
Therefore, by changing the width of pulse, we can vary the average voltage and thus control the motor speed.
E.g. In waveform 1a, the signal has a mark-space ratio of 1:1. With the signal at 12V for 50% of the time, the average voltage is 6V, so the motor runs at half its maximum speed.

6. 2. Double 555 PWM controller
The first 555 Timer creates an adjustable pulse wave with a frequency around 30Hz. 
The output of this circuit then triggers a second 555 Timer, which adjusts the width of the pulse. 
The Mark/Space can be adjusted from 0.3% to 97% of the maximum width.

7. 3. Single 555 PWM/FP controller
R1 = 1k ohm, R2 = 10k ohm, R3 = 1k ohm
VR1 = 10k ohm, VR2 = 10k ohm
Transistor = TIP 31 or 121
D1, D2 = Diode (1N4001)
C1 = 0.1F,C2 = 470F
Time on = (R1+VR1+VR2+R2)C/1.44 = from 0.14 to 1.53ms
Time off = (VR2+R2)C/1.44 =from 0.07 to 0.76 ms
For max speed VR1 = 10k and VR2 =0K (96%)
For min speed VR1 = 0k and VR2 =10K (52%)

8. Direction Control: Fwd/Rev motor ‘relay' control

9. 4. Fwd/Rev Control: H-Bridge Controller
The H-Bridge uses 2 NPN transistors which switch on if there is 5v but off if there is 0v at their base, while the PNP transistors works the opposite way round
The control inputs (PL1) A&B would be connected to PIC output pins or to a DPDT switch.
With (PL1) A=5v & B=0v current flows through the motor from (PL2) A to B
With (PL1) A=0v & B=5v current flows through the motor from (PL2) B to 0, so reverses

10. 12v Motor control with H-Bridge and 5v PIC supply

11. Stepper motor principles
A stepper motor is a “digital” version of an ac synchronous electric motor, but its position can be controlled as well as speed.
The rotor follows in sequence, the energised stator phase (need at least 2 phases) in discrete steps (the step angle) as commanded by square wave pulses.
When stopped but energized, a stepper motor holds its load steady with a holding torque, un-energised the motor must rely on its detent torque to hold the load
Drive electronics may halve the step angle by moving the rotor in half-steps.
The pulses may be bipolar (+/-) or unipolar (+/0) as shown below :

12. Stepper motor operation
Bipolar stepping motors are composed of two windings and have four wires.
Unipolar stepping motors are composed of two windings, each with a centre tap.
Permanent magnet and hybrid stepping motors are available with either unipolar, bipolar
Sequentially switching the stator phases produces a rotating magnetic field which the rotor follows in steps based on the number of poles N in the stator and rotor
Stator angle ΘS = 360o/NS , Rotor angle ΘR = 360o/NR, so step angle ΘST= ΘR - ΘS

13. Stepper motor types
The direction, step rate, and number of steps are controlled by a stepper motor controller usually an IC but could be a set of transistors.
There are three types of stepper motors in order of increasing complexity: variable reluctance, permanent magnet, and hybrid.
The variable reluctance stepper has s solid soft steel rotor with salient poles. The permanent magnet stepper has a cylindrical permanent magnet rotor (Left pic.). The hybrid stepper combines features of both and has soft steel teeth added to the permanent magnet rotor for a smaller step angle more torque (Right pic.).
The most common step sizes for PM motors are 7.5 degrees (48 steps). Hybrid motors typically are 1.8 degrees (200 steps).

14. 5. 555 Timer/4017 counter Stepper controller
Normally the PIC will be able to pulse the stepper motor driver, but below shows how a simple counter can be used.
This circuit uses a 4017decade counter/divider. The input pulses comes from a 555 timer. Each pulse, will increase one count to the This will happen 4 times, for counts 0 to 3. When in count 4, the chip will self reset (from the wire Q4 to reset) and will start over again. The first 4 outputs (Q0 to Q3) are driving the 4 transistors (e.g. Mosfets)

15. 6. Transistor based Stepper driver
In this circuit, the counter output sequence is fed into the base of a transistor to energize the winding that's connected to the transistor. 
This turns on the transistor, allowing current to pass through the winding from the 12V supply to ground, energizing the winding in the process. Inputting a logic '0' to the base of the transistor turns it off, cutting off the current flow through the winding.
This circuit shows an 8 wire hybrid motor connected in unipolar format using 5 wires

16. Motor Circuit Teams Circuits Team Circuits 1 & 4
Portugal & Czech R. (+ 1 Nr.Irl)
Circuits 2 & 4
Spain (+ 1 Nr.Irl)
Circuits 3 & 4
Italy & Romania (+ 1 Nr.Irl)
Circuits 5 & 6
Finland (+ 1 Nr.Irl)

17. Fwd/Rev Stepper Motor
Unipolar H-bridge
Bipolar H-bridge

19. Fwd/Rev 4017 Counter Stepper Controller
A 4017 decade counter/divider driven from a low-frequency oscillator (Ul-a and Ul-b) is used to drive transistor switches to sequence the windings, as is needed. MOT1 is a 12-V stepper motor. R9 and RIO are selected for the motor`s current rating. A 3.3-Hz signal from Ul will cause the motor to run at 1 rpm, 

20. Double 555 Controller Prototype Layout

21. H-Bridge Fwd/Rev Prototype Layout