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Chapter 5 , Part 3 describes the VHDL Synthesis of Electric Motor Rotation Sensor.This SENSOR gives GREEN LED output for Clockwise sense of rotation and RED LED output for anti-Clockwise sense of rotation.

DSD_Chapter 5_StateMachines_Part2_MooreMachineDesign

5.5 Designing and implementing Motor Rotation Sensor.

The customer wants a Motor Rotation Sensor. The sensor should indicate if the Motor is spinning in Anti-Clockwise (Negative) or Clockwise (Positive) direction.

Figure 1.Schematic Diagram of the Architecture of Rotation Sensing Machine.

As can seen from Figure 1 there are two Sensors 1 and 2 which are so spatially placed that they generate a square wave with 90 degree phase shift corresponding to P1 and P2. When both are ‘00’ then Negative Rotation changes this to ‘01’ and Positive Rotation changes this to ‘10’.

We will take Moore Machine Design approach. Figure 2 gives the state diagram:

Figure 2. State Diagrams ofRotation Sensing Machine.

As shown in Figure 3 , the state code is sampled and stored in the REGISTER at the lagging/leading edge of the clock pulse. The state code in the Register decides the output. Since there are four distinct STATES hence there are four distinct OUTPUTS. So we have two-bit CODE {a0 , a1} to define the four states and we have two-bit std_logic_vector output “b0b1” to define the four corresponding outputs.

The two-bit std_logic_vector input “P1P2” are obtained from the sensors mounted over the encoding disc which in turn is mounted on the axle of the rotating motor. The Clock of the REGISTER must be synchronized with the motor speed so that all the four states are continuously monitored by the REGISTER.

If S2 state follows S1 then we have LED1 lit up which signifies that negative rotation of the motor and if S3 follows S1 then LED2 lights up signifying positive rotation.

Figure 3. Architecture of Moore Type Rotation Sensor.

In VHDL representation the Moore Sensor is as follows:

library IEEE;




---- Uncomment the following library declaration if instantiating

---- any Xilinx primitives in this code.

--library UNISIM;

--use UNISIM.VComponents.all;

entity MooreMachine_Rot_Sens is

___Port ( clk : in STD_LOGIC;

______in1 : in STD_LOGIC_VECTOR(1 downto 0);

______reset : in STD_LOGIC;

______out1 : out STD_LOGIC_VECTOR(1 downto 0));

end MooreMachine_Rot_Sens;

architecture Behavioral of MooreMachine_Rot_Sens is

type state_type is (s0,s1,s2,s3);----State declaration

signal state:state_type;


process(clk,reset)---clocked process


______if reset= '1' then

____________state<= s0;--------reset state

______elsif clk'event and clk= '1' then

____________case state is

____________when s0=>

__________________if in1 = "00" then


_________________end if;

____________when s1=>

__________________if in1 = "10" then


__________________elsif in1 = "01" then


__________________elsif in1 = "11" then

Questions & Answers

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Stoney Reply
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Adin Reply
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Introduction about quantum dots in nanotechnology
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nano basically means 10^(-9). nanometer is a unit to measure length.
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Damian Reply
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s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
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Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
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for screen printed electrodes ?
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s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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what is biological synthesis of nanoparticles
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Source:  OpenStax, Digital system design using vhdl. OpenStax CNX. Apr 01, 2013 Download for free at http://cnx.org/content/col11213/1.8
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