So let's play a puzzle!
You have a bulb and a battery, and you need to make a (simple) circuit to make the bulb glow only under certain conditions.
Basic Introduction to CircuitsThink of the battery as a water pump, and wires as pipes. For everything to work, the water has to leave the pump, go through the pipes, and then return back to the pump.
Here's a simple circuit with a battery (represented by the symbol on the left) and a light bulb (or more precisely, an LED) on the right:
The "water" starts from the battery, goes around the wires, through the light, and then back to the pump. The "water" has to return back to the pump through the light for the light to be on, which it is in this case.
Now what if we split the piping?
It works too! Both lights are on!
Now let's introduce a very simple switch, the "single pole, single throw" (SPST) switch. It is either on or off:
When it's off, the pipe is cut off, so the "water" won't get to the 2nd light. Now the water can just go to the bottom and then to the right, but after it goes through the 2nd light, it has nowhere to go to return back to the pump (battery), and it cannot go back the same way it went.
Now let's introduce another switch, the "double pole, single throw" (DPST) switch. When it's on, the electricity goes through one wire, and when it's "off," it goes through another wire.
So you can turn on one light or another, but not both at the same time.
See, the other way:
Lastly, let's introduce the "double pole, double throw" (DPDT) switch. It's two of the above switches in one, but you have to have BOTH switches in a DPDT switch on, or both to be "off." You cannot have one on and the other off. See here:
In this circuit simulator I am using, it doesn't show, but normally there is a dotted line through the two above switches to indicate that both of them are together. It's supposed to look like this:
If you don't fully get it, you can try this simple circuit simulator, although it only has the first type of switch:
http://phet.colorado.edu/simulations/sims....ion_Kit_DC_Only Simulator to UseOnce you get the hang of it, you can use this simulator:
http://www.falstad.com/circuit/Some notes:
- Go to Circuits -> Blank Circuit to clear the screen
- Right click the black area to get a menu to pick what you want to add to the circuit, or right click on an existing item to get a menu to edit it
- Once you have selected something to create, click on some black area and drag to create the item
- To create wires between switches, click NEAR a switch endpoint to start (clicking on the switch will only toggle the switch)
- Find the battery in Inputs/Outputs -> Voltage Source (2-terminal)
- Find the light in Inputs/Outputs -> LED
NOTE: The LED only takes water/electrons from one end of the battery. If the light isn't turning on, try switching the way you connect the battery.
- Find a SPST (1st switch) switch under Passive Components -> Switch
- Find a DPST (2st) switch under Passive Components -> DPST Switch
- There is no DPDT (3rd) switch, but you can add two DPST switches and manually switch both together
- Sometimes, if you directly connect one side of the battery to the other side, you get a short circuit, and the simulator will say so ("Voltage source/wire loop with no resistance") -- Click the "Reset" button in the top right to restart the simulation -- Note that sometimes the simulator is stupid and thinks that there is a short circuit where there isn't
PuzzlesYou can submit your solution by posting screenshots, or drawing a schematic.
#1. Lamp #1 must glow ONLY if TWO switches are both in the "ON" position.
#2. Light lamp #1 when switch A is ON, and light lamp #2 when switch A is OFF.
#3: Turn on a light when BOTH switch A and switch B are ON, or when both are OFF, but not if one is ON and the other is OFF.
#4: Turn on a light only when switch A is ON and switch B is OFF, or vice versa. The light must not turn on when both switches are ON or both switches are OFF.
#5. Turn on a light only when ANY ONE switch out of THREE is ON, OR when ALL switches out of three are ON. If TWO switches are ON, then the light must be OFF. If ALL switches are OFF, then the light must be OFF.
#6. Have a lamp glow when at least TWO out of THREE switches are on, by using either 0 or 2 or more DPDT.
#7. Have a lamp glow when at least TWO out of THREE switches are on, by using 1 DPDT.
More to come...
