# simple/A level coursework ideas

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#### Omne

##### New Member
hey everyone was asking for some help to get ideas on how to start my design project,m was planning on making a car headlight reminder, with both audible and visual warning systems, was wondering if anyone had any ideas or diagrams on this, not to use but to give me an idea on how to start.

yours sincerely Omne

#### Gene

##### New Member
I think all successful circuit designs begin with a clear understanding of logic. Maybe it is just in your head - other times it helps to write down the possible things the circuit will have to contend with and the desired outputs.

For you, it would seem that there are 4 combinations:
input #1 input #2 output
--------------------------------------
engine on + lights off = no signal
engine on + lights on = no signal
engine off + lights off = no signal
engine off + lights on = signal (light and buzzer)

So, you asked about where you should begin, this is where I start...

BTW, what is a "simple/A level course?"

#### john1

##### Active Member
Hi Omne,

I had an old motor with a battery that was not too clever.
If i left the side lights on when i left the car, it would
not start unless i was very quick to get back.

After this had happened a few times, i decided that i had
to fix up a buzzer or something to make sure i switched
them off.

My first arrangement was very simple and very, very
effective.

It comprised of a horn relay and a silicon rectifier
between two parts of the car wiring.
It made the hooter sound if i opened the car door with the
lights on.
I very quickly learned to switch off the lights before
opening the car door.
The hooter would stop of course when i closed the door,
so if i wanted the side lights left on, that was ok.

The interior light was operated by the door switch
applying a chassis (body) connection to the interior
light circuit to make it light.

The external lights on the car all have one side connected
to the chassis (body) of the car, and require a feed from
the battery to be applied to make them light up.

On cars here, the usual arrangement is that the side lights
come on when the switch is actuated, and when the switch is
actuated further the main lights come on in addition to the
side lights. So the side lights stay on when the main lights
are operated.

The hooter is operated by a relay.
The horn relay is operated from the steering wheel by
applying a chassis (body) connection to the relay to make
it operate.

What i did was to connect a silicon rectifier diode and an
old horn relay coil in series between the interior light and
the external lights, mounted on the bulkhead under the bonnet.

This did not interfere with the hooter.
And it did not interfere with the interior light.
It was effective, although i changed it later to work
a buzzer which i salvaged from a different car.

The diode is there to reject current from between the lights.
The changes i made, i have drawn in blue.
Almost a year later i changed it to work a buzzer instead.

Best of luck with it,
John

#### Attachments

• CarBatSaver.jpg
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#### Phasor

##### Member
john, I have to say, that's a fantastic idea - I've often thought of doing a similar thing in my car, but have never thought of anything quite so simple - and often, simpler is better! 8)

#### Gene

##### New Member
Gee, I thought all cars made in the past 5-6 years already had a lights-on reminder installed at the factory. A ready-made device (with 2 connecting wires, buzzer, and instructions) is available at auto parts stores in the US for under \$5 as an add-on for older cars.

I still think it makes for good investigation as a science project.

#### john1

##### Active Member
Thank you Phasor,

The circuit started with much more in it.
It took me a while to trim it down.

Cheers, John

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