Project help

[Ryan Harding]

Hi, i have a friend who is currently undergoing his GCSE project. For the people who dont understand GCSE's, its the examinations for 15-16 year olds. The english first recognisable grades, im unsure of what the equivelant of this is to the USA or any others.

He is doing resistant materials, wood/metal/plasitcs. His task is to create a wooden toy that moves, something along these lines. He has asked me to install some basic electronics in a tractor!

So we have brifely talked about what may be 'acceptable?' Basically practable and actually useful

The ideas so far are, in my opinion, very basic electronics:

Headlights! - I think that this maybe is boring and un origional! So i think that a simple circuit using some resistors, transistor and an LDR would be more useable? No switches, and in my opinion more impressive!

Most tractors, here in the U.K, have orange flashing lights on the top. A flashing orange LED would fit right in here, ideal.

This is one that i am unsure about:

2 Red LED's that light up when the tractor is reversing, and a buzzer that buzz's for a second and then stops, starts etc, maybe with a 555 chip? I'm unsure of this as the vehical is mechanical, not electronic so i dont know how it would sense that it is reversing?

Suggestions for that would help me alot.

Now to the problem that i am really after!
(You didn't think that was all did you )

I have made the 'automatic headlamps,' before. Not for the same purpose, more for experimental purposes, but i'm sure that it can be modifyed to suit the needs.

I have the following circuit that i used, but im unsure of what parts to have!

1) The battery and im guessing can be 2x 1.5v batteries? 3v is enough to run this small circuit?

2) What is the differnce in LDR's, i have only used them once, and was given the part.

3) Transistor. I have used one of these in the circuit and know for a fact that it was a 'NPN' transistor. It came on at 0.6v, sorry if this is wrong, im new to transistors, havent used them much at all!

So an over view of what im asking, is there a way for the reversing plan, to be put into action?

What circuit components would i need to make the automatic headlights?

Sorry if you find this post is too big, i just dislike it when people post and dont give the whole story, it leaves questions un answered and people irritated!!

Thanks very much,

Ryan Harding

 

[-=GST=- Nemisis (cs/cz)]

555 astable here, change the push switch for a the reverse lever or something and the capacitor dictates flashing speed.

 

[Ryan Harding]

that would be ideal for the flashing led, but i can just buy a flashing led
i've made that circuit aswell, crop clips by any chance

 

[zachtheterrible]

U know wut would be cool, is if the headlights came on wen u go forward, and the tailights come on wen u reverse (i dont know if thats what u already said). You could make it so that when the the wheel goes forward, it flicks a switch one way, and when it goes the other way, it flicks the switch the other way.

Transistor. I have used one of these in the circuit and know for a fact that it was a 'NPN' transistor. It came on at 0.6v, sorry if this is wrong, im new to transistors, havent used them much at all!

What do you want to do with the transistor??

 

[Exo]

1) The battery and im guessing can be 2x 1.5v batteries? 3v is enough to run this small circuit?

Yes, they would do fine...

2) What is the differnce in LDR's, i have only used them once, and was given the part.

Their resistance for a certain light level, you need to find out the resistance of your LDR for the light level you want the headlamps to turn on.

3) Transistor. I have used one of these in the circuit and know for a fact that it was a 'NPN' transistor. It came on at 0.6v, sorry if this is wrong, im new to transistors, havent used them much at all!

I would't find the circuit you posted a good solution, it hasn't got hysteresis.
Your circuit will make the led (wich needs a current limiting resistor in series btw) go on and off repeatedly when the brightness reaches the threshold level.
Adding hysteresis will turn the light on at a certain dim light level, but will turn it off at a higher light level, to prevent 'clattering' at the switch point.

 

[Ryan Harding]

OK, thanks for all the input!

I really need to see his designs before i can adjust it, he doesnt work in school much though :roll:

What is hysteresis?

Thanks

 

[Exo]

What is hysteresis?

Like I said, Hysteresis just means that the turn-on point is higher then the turn-off point. In your circuit the point where the light turns on, and the point where it turns of is the same (above it is on, below is off). When the light level is at that point yout lamp will be switching on and off rapidly, adding hysteresis prevents this.

Take a look at
**broken link removed**
section 9.3