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DYNAMIC SPEED GOVERNORS
Introduction
With the of aim of dynamically limiting the speed of the vehicle to a preset value.
Presently available option-Static governors.
Static governors have the limitation of setting the maximum speed of the vehicle.
The main idea is to transmit the speed limit for the area to the vehicle, as it approaches an area that has speed restriction, so that the driver can be warned and the speed of the vehicle is automatically reduced.
An RF transmitter used in the system transmits a speed limit to the approaching vehicle and the RF receiver inside the vehicle receives this signal.
The comparator present inside the vehicle compares the received speed and the vehicle speed to give an output.
This output can be used to control the governor in the vehicle there by controlling the speed.
Components of the System
RF transmitter unit (HT 640)
Sensor unit
RF receiving unit(HT 648)
Digital tachometer unit
Seven segment display device
Display drivers
Comparator
Alarm unit
Objective
The primary design criteria for this project work were as follows:
Incorporate easily available components
Use cheap and easily worked materials platform
Minimize the weight of the unit
Maintain a level of robustness
Bring about solid design and construction features
Limit the consumption of energy
Modular design
Block Schematic of Transmitter Section
Block Schematic of Receiver and Tachometer Section
RF Transmitting Unit
Consists of
A sensor unit
Transmitting unit
First section consist of a sensor unit, mono-stable vibrator, astable multi vibrator.
Sensor unit consists of a LDR and photo diode.
Followed by a mono-stable vibrator and astable vibrator.
Receiver Module
Seven Segment Display
NUMBER OF PULSES TO SPEED (KM/HR) CONVERSION
Speed in km/hr = distance traveled in km in 1 hr.
Also, speed in km/hr = distance traveled in km in (1/a) hr × a
Where ‘a’ is the scaling factor and (1/a) hr is the measuring time.
Now, distance travelled in (1/a) hr = number of rotations in (1/a) hr × 2π × radius of wheel.
Counter value = D1hr = D (1/a) hr × a
= 2Nr× π ×r×a
But counter value = number of pulses counted = Np
Hence Np = 2Nr × π × r × a.
Np/Nr= 2 π × r × a.
We take Np/Nr = 1 i.e. no scaling which means that sensor output is directly coupled to counter.
Therefore, 1 = 2 π ×r × a
a = 1/(2 π ×r).
Here we take the radius of the wheel as,
22.5 cm = 22.5×10-5 km.
Value of a = 1/(2 π × r) = 707.35
Hence measuring time = (1/a) hr
= 3600 sec/707.35
= 5.08 sec
Therefore the measuring time is approximately taken as 5 seconds.