Download Water Flow

SECURITY CIRCUITS
YOUR MISSION: Create a security
system using the Electronic Snap
Circuit Kits. Each team needs to
design a system that will include
at least one sensor and two ways to
alert that there is an intruder
(sight, touch, hearing).
The more sensors and alarms
included the better!
SECURITY CIRCUITS
• Sensors include: photoresistor
(light detector), microphone
(sound), press switch (touch)
• Alarms include: whistle chip,
speaker, music circuit, space
war circuit, alarm circuit,
motor (fan), LED light, lamps
Ohm’s Law
•
•
•
•
If You compare electricity to Your house water system:
Voltage is a Water Pipe
Current is a Water Flow
Resistance is a Valve(or a tap)
•
Now, You can imagine that the bigger the Water Pipe the
bigger Water Flow is.
Same with electricity, the bigger the Voltage, the more
Current You can get.
•
•
If You have a Valve(or a tap) You can reduce Water Flow
with it because size of the Water Pipe is reduced at
that spot (if You get what I mean), hence with
Resistance (Resistor) you can reduce Current by creating
a Voltage drop at a certain spot in a circuit.
Ohm’s Law
• I - Current
• V - Voltage
• R - Resistance
Transistor
•
•
•
Let's see if I can do better. Here is a picture of a
transistor. My transistor runs on water current. You see
there are three openings which I have labelled "B"
(Base), "C" (Collector) and "E" (Emitter) for
convenience.
We provide a reservoir of water for "C" (the "power
supply voltage") but it can't move because there's a big
black plunger thing in the way which is blocking the
outlet to "E". The reservoir of water is called the
"supply voltage". If we increase the amount of water
sufficiently, it will burst our transistor just the same as if
we increase the voltage to a real transistor. We don't
want to do this, so we keep that "supply voltage" at a
safe level.
If we pour water current into "B" this current flows
along the "Base" pipe and pushes that black plunger
thing upwards, allowing quite a lot of water to flow from
"C" to "E". Some of the water from "B" also joins it and
flows away. If we pour even more water into "B", the
black plunger thing moves up further and a great
torrent of water current flows from "C" to "E".
Resistor
• Resistors “resist” the flow of
electricity and are used to
control or limit the
electricity in a circuit.
Increasing circuit (+)
resistance reduces the flow of
electricity. Materials like
metal have very low resistance
(<1Ω) and are called
conductors, while materials
like paper, plastic, and air
have near-infinite resistance
and are called insulators.
Capacitor
• A capacitor is considered a
"passive" device because it
does not actively affect
electrical currents or other
electrical components. Instead,
capacitors store electrical
energy between electrical
conductors.
• The numbers printed on the
capacitor refers to the amount
of current it can passively
hold. (Ohm’s Law!)
• Capacitors help regulate
electrical current.