Remote Controlled Switch

I was watching the show Mythbusters the other day and saw that Grant had constructed what appeared to me as a RF (Radio Frequency) remote. I'm pretty sure this was what is was because it had one of those big ol' remote car controls that you buy. So i was wondering if anyone in here knew about RF and if they could maybe explain it to me abit? Grant used the remote to toggle a shotgun firing, but I want to make one just for hah-hahs .

Also, I was curious if there was a way that i could build something that simulate the effects of blinking lights like on a Christmas tree. I would presume this would have to have a timer of some sorts that stops the flow of AC current from the socket and starts it again in about .5 of a second. but I have no idea on how you would be able to do this.

Any info would be appreciated as I wish to learn more.

I believe that RF has two frequencies - analog and digital. If I remember correctly (learned this a long time ago in Information Technology class in grade 12), analog has a wider bandwidth than digital. The wave current in analog is larger, and digital is more narrow. But since analog's wave is larger, it cannot contain as much information as digital.

And I believe something with binary codes is embedded with both analog and digital that makes them different from each other. I can't remember anymore.

There are many frequencies which make up the RF spectrum:

Ultra Low frequency (ULF): 0-3 Hz
Extremely low frequency (ELF): 3 Hz - 3 kHz
Very low frequency (VLF): 3kHz - 30 kHz
Low frequency (LF): 30 kHz - 300 kHz
Medium frequency (MF): 300 kHz - 3 MHz
High frequency (HF): 3MHz - 30 MHz
Very high frequency (VHF): 30 MHz - 300 MHz
Ultra High frequency (UHF): 300MHz - 3 GHz
Super high frequency (SHF): 3GHz - 30 GHz
Extremely high frequency (EHF): 30GHz - 300 GHz
<300GHz

Anything above 300GHz is useless, the Earth's atmosphere absorbs the electromagnetic radiation.

Radio's work by transmitting a signal at say, 70 MHz, and than any receivers tuned in at the same frequency will receive the information from the transmitter.

Mythbusters is a pretty cool show. Me being king of the techno-geeks, anytime it's on, I actually pay attention without any sarcastic comments and without getting bored and turning it off (I hate TV, but my sisters are all addicted to it. They spend most of their time in front of the TV, I spend most of my time across the room in front of the computer).

And, moving on...
Radio waves are magnetic pulses that move throughout the air around us. At this very moment, hundreds, maybe thousands, of radio waves are passing through your body without leaving any kind of lasting proof that they were there.
An antenna doesn't receive just the radio wave that it's supposed to (i.e. a remote-controlled car receiving the radio wave from the remote), it receives all of the radio waves around it. When a radio wave strikes a metal rod like an antenna, it causes the antenna to vibrate, but it vibrates so little that no human can sense it in any way without mechanical help.
An antenna is hooked up to a closed electrical circuit (meaning that it has electrons flowing through it), and when the antenna vibrates, it alters the flow of electrons slightly (i.e. slight breaks in the current where the antenna vibrated back and forth). The electrons then pass through a bunch of capacitors and resistors that work together to dispel resistance and build up resistance (electronic resistance being measured in ohms), that together change the voltage, or electronic pressure in a circuit. The current then flows through a series of transistors.
Transistors are little bits of silicon and scrap metal that act as self-changing switches. When the voltage passing through a transistor reaches a certain point, the transistor will switch from the "off" position to the "on" position, and the electricity will flow through the new path opened up. So, when the electrons that have been altered by the vibration of the antenna and altered again by the capacitors and resistors flow through the transistor, since the voltage in the current has been changed by the antenna, it flows through the "on" position of the transistor, instead of back through the battery by the "off" position.
The "on" position of a transistor in a RC circuit is usually hooked to a motor or a light, so that when the certain speed of vibration in the antenna caused by the frequency and wavelength of a wave is received, it will perform its specified operation. In this way, if you have two objects operating on the same frequency, and one of the objects is in the range of the other objects' controller, you're going to get some undesired results, because of the different commands that the other object can have for the same frequency as the first object.
So, when a specific vibration is attained in the antenna, the transistors will change positions and the electricity will flow through the newly opened path, through the intended object, and then back to the battery. Think of it as taking a detour on a highway; you still get where you want to go (back to the battery), but you take a different path that is a farther distance and a longer time is spent traveling.

And that's the basis of radio-controlled devices. If you're going to build one (or steal one off an old electric appliance, I do that a lot), you need to make sure that the receiver is contstructed with the right amount of components needed to receive the vibration from the transmitter. I've been trying to build a radio transmitter/receiver pair for a while here out of parts from an old wireless phone and parts from an RC car. I haven't been too successful, but that doesn't mean I'm not going to give up!

And now for your second question:
Timers that change every so often in a set amount of time also use transistors, but they include an oscillator (usually a bit of quartz crystal) to count time as well. Without an oscillator, you would have to count 9,000,000,000,000,000,000 (nine quintillion) electrons flowing through a given point in a circuit, and then 1 second would have elapsed. With an oscillator, you only have to count a couple hundred rotations before a second elapses.
So, an oscillator is hooked to an electrical circuit, and it vibrates, or oscillates. A cleverly controlled IC (Integrated Circuit) counts the oscillations, and when a certain amount of oscillations is counted, a final transistor will switch from off to on, and the current will flow to the operation desired to happen every so often.
You can buy timers in set quantities of time that tell you where to add the power, and how to hook up your circuit, and they do all the rest of the work for you (RadioShack, anyone?). If you actually want to build an oscillator circuit, I can't help you. RadioShack is good enough for me.


I know that's a lot of information, and it may have been slightly confusing for you (it's just a bit confusing for me too, on account of sheer quantity). If you want me to give you a simpler version of the same content, or if you have any more questions concerning electronics, feel free to contact me. In the meantime, I hope I helped.