Section Two Flashcards
What is a schematic?
Representation/diagram/blueprint of a circuit
Schematics for wires crossing
wire
When two wires cross but are separate the schematic will show:
the lines crossing through each other
a hum over the crossed wires
When two wires are together and part of the same circuit:
they will have a dot in the middle of them.
Schematics:
Circle with + and -
for lines sort of like ||||
DC power source
Long line Positive
Short line Negative
Schematics:
Circle with wavy line inside
AC
Schematics:
Four peaks, like a heart monitor
resistor
Schematics:
Play button with a line in front >|
LED
anode >| cathode
How do switches work differently
What is the schematic for a switch?
What is SPST
What is SPDT
What is DPST
a dot and a lifted line, a dot on the other side of the wire it will go to if switched. If it’s on, just close the flap in your schematic
_/ _
SPST single pull single throw
SPDT single pull double throw (off connection one wire connected, on will make it connect to a different one)
- schematic for this would be the same as the first but two connection that it can go to
DPST double pull single throw (Two separate connection. When off neither are connected. When on both are connected)
DPDT double pull double throw (One push will turn on two SPDTs)
What is a pull and a throw?
pull - connections that you can make. Single can connect one or the other. Double can connect two or more circuits on and off.
throws - number of positions switch can support. Single will connect one wire to another, either on or off. Double can connect two sets of wires in either on or off. You’ve doubled the things you can throw that power to.
What are the wands called on the multi meter?
probes
If you don’t know how much current is running through a circuit, what setting do you use?
The highest reading (apparently 10 is more than mA - that’s mili-amp)
The multimeter becomes part of the circuit
How do you measure amps?
Red probe -> positive power source
black to anode of led
It completes the circuit
What is Ohms law
V = I R
voltage = current * resistance
There are several variations though. You just need to know the answer of two of these variables.
so
I = V / R
or
R = v / I
Power vs Wattage
Power - rate of energy usage (P)
Wattage - Unit of measurement of power (w)
The more wattage, the more energy consumed.
1/4 watt rated resistor - can handle .25 watts without getting hurt
P = V * I
So, how much power does the LED from earlier have?
it takes 3.2 volts
and uses 24mA (miliamps) or .024Amps
sooooo
3.2 * .024 = 0.0768 watts (The amount of energy it uses)
What is a series circuit?
Just a simple loop
This is fine for certain things. But if you have a loop that connects to a fridge, then a coffee maker, then a toaster, and you unplug the coffee maker you gots no electricity
Current is the same at all points
Voltage is different
What is a parallel circuit
Multiple paths electricity can take
Most common
Current differes
Voltage stays the same
What is the total resistance in a series circuit?
All resistances added up
More resistors, the resistance goes up but the amps goes down
What is the total resistance in a parallel circuit?
1 over resistance total = 1 over r1 + 1 over r2, etc
If you add more resistors the total resistance decreases
but the amps goes up
Find the least common denominator(the number that all the bottom numbers can be divided into) convert the fractions.
Add the tops (numerator is top bottom is denominator)
The answer is the reciprocal (flip the two numbers in the fraction)
1/r 1/r 1/r = x
x + last resistor
How do you find the total current in a parallel circuit
Voltage over total resistance
If you add a resistor prior to the parallel circuit, how do you calculate ohms?
https://www.youtube.com/watch?v=DYn3tn00VK0&list=PLah6faXAgguOeMUIxS22ZU4w5nDvCl5gs&index=17
add the ohms of the resister to the added ohms of the parallel circuit.
You treat them like one big resistor
How do you calculate the voltage drop for a parallel circuit that starts with a resistor before it gets to the parallel circuit?
Voltage drop = I * Resister(the main one)
Subtract the main voltage by the answer to the above and you’ll know how much voltage will be distributed (and stay the same) to the parallel circuit
What is a potentiometers
Resister that is dependent on how it is turned
Three terminals (you can call your wires that too)
The two outside terminals are connected by a material that is a resistive material.
The middle terminal is standard wire.
A wiper connects the resistant material to the middle terminal. The closer to the start of the terminal that the wiper is, the shorter distance the electricity has to travel to get to the middle terminal meaning less resistance.
What is the schematic for a potentiometer?
The resistor symbol (Several peaks) and an arrow pointing to it below
Middle up arrow represents the middle terminal.
What do capacitors do?
Store electrical charge, like little batteries.
Long lead = anode
Short = cathode
OR
Stripe with negative symbol. Closest lead to that is cathode
What does the voltage mean on the capacitor?
Max voltage it can be used for. Don’t go over it.
What is a ceramic Disc Capacitor?
Not polarize, you can use either lead for whatever you want.
What is a poly file capacitor?
Look like those little square colored pieces of gum.
Not polarized, use whatever leads you want.
What is the schematic symbol for capacitors
–| |– <- not polarized
–| (– <- polarized like electrolytic capacitors
| < - anode
( - Cathod
What unit of measurement are Capacitors measured in?
Farads (F)
µF - micro farads - 0.000001Farads - one millionth of a fard
nF - Nanofarad 0.001 of a µF
What is the rc time constant in terms of capcitors??
tau = Resistance*Capacitance
so ohms * farads
This is the time it takes a capacitor to charge 63%
98% after 4 tau periods
What happens when you have 2 capcitors in series?
What about 2 capcitors in parallel
1/f1 + 1/f2
f1 + f2
It’s the same as resistors formulas except flipped around
What is a diode?
->| Cathode on the end here
Flows from anode to cahtode
If done the other way it will try and stop it`
What is it called when I diode is facing the proper way?
What about when it’s turned around
Forward Bias - Allows current to flow through
Reverse Bias - Won’t allow current to go through.
What happens if you have a diode in reverse bias and try to pass more voltage than it’s voltage limit?
The diode will break, this is called ‘breakdown’
This is no bueno
How much voltage will your diode cause the voltage to drop?
As many as it takes up. That’s all gone now :(
What is the cathode side of the diode?
The stripe side
How to tell how much voltage something is taking up
probes to pos and neg of component
