OPTO ELECTRONICS   

An exciting new  challenge for students involved in FS2000

OPTO ELECTRONICS
A South East England Development Agency Project 
which aims to encourage the understanding and use of Optoelectronics in schools 

What is OPTOELECTRONICS?

Optoelectronic devices are devices in which the photon  (the basic particle of light), is affected. These devices can be divided into two main groups
1. Devices which convert light into electrical current or electrical current into light:
- photodetectors and solar cells that convert photons into electrical current,
- light-emitting diodes and semiconductor lasers that convert an applied voltage into emitted photons,
2. Devices which Transmit light
 - optical fibres that guide light within a small plastic or glass fibre between a light source and a detector
- optical-fibre amplifiers that convert the energy of an optical source to photons identical to an
  optical signal.

Why use it?
For us to be able to analyse how the engine is working we must know certain pieces of information. Performance needs to be measured in a way that means it can be compared to data from manufacturers, other engines or cars.

  • Car performance is best measured in distance & time
  • Engine performance as power and revs

Another vital statistic for us to know is engine temperature.
Many of the cars we see taking part in FS 2000 do not take into account how the engine might be most effectively cooled so that it works at its correct temperature.

 

To obtain this information we will face problems:

  1. The engines work at very high revs, 28,000 rpm being the maximum that our engine operates at. Trying to use a mechanical device to count this is not realistic,
  2. This information is best obtained when the car is under race conditions, i.e. on the track.
    Communicating this data gives us a problem
  3. Engines work in a hostile environment, meaning they are hot, oily, and vibrate.

Using electronic systems is the preferred method as it is accurate, reliable, small and light.
It gives us the flexibility to use signals as an input to a data-handling package on a computer.
We are going to capture data from our cars.
Warm Up Project
Use a test device to carry out tests of infrared remote controls used in television sets, stereos, and videos etc

Project 1
Engine speed and temperature sensor and display system.

Project 2
 Engine power

Project 3
 Accurate measurement of distance covered by a car and the time taken


Prototype circuits and a more coventional Opto device.....an infrared remote control

Let's look at the Warm Up project in more detail.
 You know how frustrating it is when you try your remote control and nothing happens, is the controller working, are the batteries flat or is there a bigger problem? Now you have a test device.

Using this circuit you can carry out tests of infrared remote controls used in television sets, stereos, and videos etc. Infrared light will cause the LED to switch on.

Components list;
T1,T2 transistors BC 308
T3 photo-transistor 
LED light emitting diodes
C 1 capacitor 100 pF.
C 2 electrolytic 47uF
R1,2,4 270 Ohms
R3 1M

Construction notes

Both daylight and artificial light include a considerable proportion of the infrared spectrum, therefore the infrared detector will react to ordinary daylight. To overcome this, place the photo-transistor into a black cardboard tube approximately 50mm long and 4mm in diameter.
To test for infrared place remote controls etc at distance between 3 to 10 cm in front of the photo-transistor.

Let’s look at project 1 in more detail.

How does it work?
We need to count the revolutions of the engine using a optical switch, this is done with a disc with light and dark segments. The light part reflects the light from an infra-red LED whilst the dark absorbs it,  giving a pulsed signal. This is detected by an optical 'tacho' sensor.


Prototype circuit built on Breadboard


This signal is too fast for our counter to receive, so we 'stretch' the signal by using a 555 chip.
The signal can then be picked up and read by the driver chip for the counter display.
Finally the circuit has a 'clock' to allow the signal to be sampled for a period of time, then displayed, then sampled then displayed and so on.
The unit can be tested by using the remote control from a T.V or video.

From this prototype you will be able to design features which make it easier to use, more reliable, able to display different data etc.

Let's look at Project 2 in detail

Prototype Dynomometer for measuring engine revs and power.

Let's look at Project 3 in detail

We all want to know how fast cars really are? Don't we? 
Through the OPTO Electronics work that some schools are taking part in, 
cars (or anything else) can be timed to the nearest 100th of the second now. Nearly Formula One standard where 1000th of a second sometimes separates the cars, that's certainly better than stopwatches! 

The principle is a very simple one, a car will break a light beam between a source and a detector. However we want a very precise light beam and we want it to work in all weather conditions, we also want an electronic signal to start and stop an accurate timing device. Enter the LASER!

The laser module we will be using will give a 7 mm diameter spot at a distance of 5m, no race track we are using is over 5 m wide! In fact the laser has a range of 50 m but by then the spot will be further diffused. It is a safe device to use so long as you’re not stupid enough to stare directly into the laser beam. You can use this light gate across the start finish line to measure lap times or you can use two beams and measure distance apart to carry out a distance / time trial in a straight line, say 100 m. With this accurate timing information you will be able to further develop your driving skills and car performance. 
Does it really make a big difference if you got huge wing on the back??
Is Chris really better than Abi ? Or is it just that he’s a big head and thinks he can drive better?? 
Contact the TEC if you want to borrow a LASER timer to see just how fast you really are.