safety lights

7/29/2019 safety lights

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Design Brief

Design and make a pedestrian / cyclist safety light.

The safety light must be programmed to flash highbrightness LEDs on and off.

Research homework:Complete research to enable you to decide what type of

product you will design. Areas of investigation shouldinclude:

Research of pedestrian/cycle safety products already onthe market that utilise LEDs or that could be developedto utilise LEDs

Research of the situation why would

cyclists/pedestrians need a safety light?


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The E.R. Thomas Motor Company's

"Auto-Bi" or "Auto-Bike" began

production in 1901, making E.R.

Thomas one of the first manufacturers

in the United States to mass-producemotor driven cycles.

Auto-Bi Kerosene

Headlamp


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Design Specification

Points to include:

The design will use a PICAXE-08

microcontroller as its controller.

The design will include 3 high brightness LEDs.

The design will be able to optionally react to

changes in light levels.Add further points that are of importance to

your target market and research


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Printed Circuit Board

Track SideThis side contains the circuit

(tracks) that joint the

components together

Component SideThis side is where the components

are (usually) mounted


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Fixed resistor

This fixed resistor has a fixed

resistance which is indicated

by a colour code.


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2

3

? ?

1

330 (ohms) 4700 (4.7k)

47000 (47k)


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Light Emitting DiodesThese can be red, green,

amber or yellow in colour.They must be connected

the right way round.

The positive leg of an LED is longer

than the negative leg.

The negative leg also has a flat edgeon the plastic casing of the LED.


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A battery (cell) is a self-contained source of electrical energy.

It is a portable power supply.

Batteries contain chemicals that store energy.

When connected into a circuit this chemical energy is converted

to electrical energy that can then power the circuit.

Batteries and Battery Box


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Slider Switch

Used to switch the circuit On or Off


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Microcontrollers are purchased blank and

then programmed with a specific

control program. Once programmed the

microcontroller is built into a

product to make the product more intelligent

and easier to use.

Microcontrollers are used as the brain in

electronic circuits.

Microcontrollers are used in automatically

controlled products and devices, such as

automobile engine control systems, remote

controls, office machines, appliances, power

tools, and toys.

Microcontroller


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IC Socket

IC sockets provide an advantage over directly

attaching microcontrollers to the PCB by

making it easier to replace the processor in the

event of a failure. The microcontroller is often

the most expensive component in the system

and the cost of a IC socket is relatively low.

The IC sockets is soldered to the PCB and

The microcontroller is plugged into it.


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Download Socket

The download socket is used to connect

the PCB to a computer.

The programme created on the

computer can then be downloaded to

the microcontroller


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A Light Dependent Resistor (LDR) is special

type of resistor that reacts to changes in light

level. The resistance of the LDR changes as

different amounts of light fall on the top

'window' of the device. This allows electroniccircuits to measure changes in light level.

Light Dependant Resistor - LDR

LDRs are used in automatic street lamps to

switch them on at night and off during the

day. They are also used within many alarm and

toys to measure light levels.


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Safety Light Components

PCB printed circuit board

R1, R2, R3 120R resistor (brown red brown gold)

R4 10k resistor (brown black orange gold)

R5 22k resistor (red red orange gold)

R6 10k resistor (brown black orange gold)

LED1, 2, 3 High brightness LEDs SW1 On/off slide switch

IC1 8 pin IC socket

IC1 PICAXE-08 microcontroller

CT1 PICAXE download 3.5mm socket

BT1 3V (2xAAA) battery wire To connect LEDs

LDR Miniature light dependent resistor


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Component positions are printed on PCB


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Place the three 120 (brown red brown gold) resistors in positions R1, R2 and R3

R1

R2

R3


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Place the two 10k (brown black orange gold) resistor in positions R4 & R6.

R4

R6


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Place the 22k (red red orange gold) resistor in position R5

R5


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Push the download socket onto the PCB and make sure it clicks into

position (so that it lies flat on the board).


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Push the IC socket into position.

Make sure the notch at one end points towards the resistors.

Notch


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Solder the slide switch in position.


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Place the first LED into position marked LED1

Make sure the legs are in the correct positions.


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Make sure the bottom of the LED is level with the top of

the switch i.e. the LED is about 6mm above the PCB.

6 mm


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Bend the LED around the edge of the PCB so the LED

is now on the track side of the PCB


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Connect the wires from the battery case in the position marked BT

Note: Black = negative & Red = positive


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Cut 4 wires (2 red, 2 black) 100mm long.

Solder one red (+ve) and one black (-ve) wire to LED2 & LED3

Slide on insulating tubing.

Long leg +ve

Short leg -ve


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Solder the other ends of the wires from the LEDs to the PCB


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Remember red +ve & black -ve


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Solder the Light Dependant Resistor LDR on the TRACK side of the board.

It should be left raised on legs approximately 5mm above the board.

5mm


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Location of LDR viewed from component side.


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Insert the microcontroller into the socket,

ensuring the notch faces the resistors.

Notch


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Programming the Safety Light

To create a programme to control how the safety light will operate we will be using

computer program called PICAXE

To create the program we will be using a programming language called BASIC

This program will then be downloaded to the microcontroller (the brain) on our

safety light


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BASIC Language (1)

The three LEDs in the safety light are numbered LED1=0 LED2=1 & LED3=2

All BASIC programs should start with a label.

A label is a name followed by a colon (:) for example;

main: or start:

English Language

switch on LED number1

switch off LED number1

wait for 1 second before going to next command

go back to the beginning of the program

BASIC Language

high 0

low 0

wait 1

goto main


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Program to check LEDs

main:

high 0

wait 1low 0

wait 1

goto main


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BASIC Language (2)

The LDR (light dependant resistor) in our circuit is called pin3It has a value of1 or0

1 - if light is falling on it

0 - if there is no light

Therefore the BASIC command pin3 = 1 means light is falling on LDRand pin3 = 0 means no light is falling on LDR

LOGIC commands, such as if then. commands can be used in BASIC

We can say; if(something is true) then (do something)LOGIC commands make the brain of our circuit more intelligent


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Program to check LDR

main:

if pin3 = 1 then goto LEDon

low 0goto main

LEDon:

high 0

goto main


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BASIC Language (3)

The wait command, used earlier, uses whole second units.

wait 1 means wait for 1 second

wait 2 means wait for 2 seconds etc.

If you want your program to wait for a fraction of a secondthen you must use the pause command.

The pause command uses 1 millisecond units (1000 ms = 1 second)

Examples

pause 1000 means wait 1 secondpause 500 means wait 0.5 seconds

pause 100 means wait 0.1 second

pause 1500 means wait 1.5 seconds


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Program to sense Light or DarkThis program has a main loop which flashes the LEDs on and off fairly slowly.

If the LDR light sensor is in the dark the LEDs will flash on and off much more quickly.slow:

high 0

high 1

high 2

pause 500

if pin3 = 0 then goto fast

low 0

low 1low 2

pause 500

if pin3 = 0 then goto fast

goto slow

fast:

high 0

high 1

high 2

pause 100if pin3 = 1 then slow

low 0

low 1

low 2

pause 100

if pin3 = 1 then slow

goto fast

Label for slow flashes

switch on LED 1

switch on LED 2

switch on LED 3

wait for 0.5 seconds

if it is darkgo to fast flashes label

switch off LED 1

switch off LED 2

switch off LED 3


if it is darkgo to fast flashes label

go to slow flashes label

Label for fast flashes

switch on LED 1

switch on LED 2

switch on LED 3

wait for 0.1 secondsif it is lightgo to slow flashes label

switch off LED 1

switch off LED 2

switch off LED 3


if it is lightgo to slow flashes label

go to fast flashes label


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Advanced BASIC Language (4)

Sometimes it is useful to switch more than one LED on or off at the same time.

This saves time when lots of high and low commands would have to be used together.

The command that does this is called let pins =

After the equals sign a number is used. Each LED is given a value, and the number

used in the program is the sum of these values.

LED3 LED2 LED1

Number(high/low) 2 1 0

Value 4 2 1

Switch on all LEDs

Switch on LED1 & LED2Switch on LED2 & LED3

Switch off all LEDs

let pins = 7

let pins = 3let pins = 6

let pins = 0

Note: Before the let pins = command can be used all LEDs must be switched off

So your programme MUST start with low 0, low 1 and low 2


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BASIC for. next loops

If we want to switch on a LED a specific number of times

we can use a for next loop.The for next.. loop uses a counter or variable.

The PICAXE software can use 14 variables from b1 to b13

Example switch on LED1 15 times then stop.

main:

for b1 = 1 to 15

high 0

pause 500

low 0

pause 500

next b1

end:

Advanced program


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Advanced programThis program uses a number of

for...next loop to create

a number of different patterns.

start:

low 0

low 1

low 2

main:

for b1 = 1 to 20

let pins = 7pause 100

let pins = 0

pause 100

next b1

for b1 = 1 to 20

let pins = 0

pause 200let pins = 1


pause 200

let pins = 7

pause 500

next b1

for b1 = 1 to 20

let pins = 1

pause 100

let pins = 0pause 100

let pins = 2

pause 100

let pins =0


pause 100

let pins = 0

pause 100

safety lights

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