Simplest transmitter and receiver circuit ?

Discussion in 'General Electronics Chat' started by curry87, Aug 20, 2010.

  1. curry87

    Thread Starter Member

    May 30, 2010
    Im looking for the simplest transmitter and receiver circuit that can be built that act in the same way as good old morse code but instead of having a speaker at the receiver end have a led that lights instead.Only want a few meters range ideally,is it possible to design it without a crystal literally using the bare amount of parts ?
  2. marshallf3

    Well-Known Member

    Jul 26, 2010
    Simple enough. Look up the circuit for any wireless AM or FM transmitter and modulate the microphone input with any sort of oscillator in the audio range, then simply use an old portable radio as your receiver.
  3. Audioguru


    Dec 20, 2007
    A child's walkie talkie has only 4 transistors and costs almost nothing. Nobody uses Morse code today so you will need to modify it so it clicks instead of talks.
  4. marshallf3

    Well-Known Member

    Jul 26, 2010
    Actually if I recall the last ones I looked at had built in morse code buttons on them. $2.99/pair at the Dollar store.
  5. count_volta

    Active Member

    Feb 4, 2009
    You said the simplest.

    In theory this is the simplest transmitter possible. ;)

    By tapping the terminals of a 9-volt battery with a coin, you can create radio waves that an AM radio can receive!

    You are creating a changing electromagnetic field, i.e. a radio signal. I know this is not what you meant, but I remember reading about this one time and was amazed at how simple radio waves really are. Apparently any AC signal emits them!!! If you have an AC signal with frequencies close to the radio frequencies you might get interference.
  6. retched

    AAC Fanatic!

    Dec 5, 2009
    What kind of Dollar store has prices of $2.99?

    Wouldn't that be the $2.99 store?


    As for you led opposed to speaker requirement, If you used a neon indicator, that could be as easy as swapping the speaker with an indicator.
  7. curry87

    Thread Starter Member

    May 30, 2010
    Can someone please suggest a circuit design to this problem.Say i have a switch on a door that is closed when it is open this sends that signal to a transmitter then to a receiver wireless located 3 meters that lights up an led ?

    What circuit requires less components am or fm receiver transmitter ?
  8. tom66

    Senior Member

    May 9, 2009
    There are things called ZigBees which act as transmitters on the 2.4GHz band. You can send serial data over them. Because of the low power they are completely legal to operate without a license. But beware of interference in this band especially from WiFi, microwaves, etc. which all use 2.4GHz. You still need a microcontroller on either end to send and receive data.
  9. marshallf3

    Well-Known Member

    Jul 26, 2010
    They just call them that around here, we actually have three major variations. Inone every item is priced at exactly $1, another it's in multiples of $1 and the third is srot of multiples of a dollar but everything ends in .99

    Neon takes up to 95 volts before it ionizes and starts conducting, an LED will usually light to some extent when plaed across speaker terminals.

    But honestly, I've seen pairs of walkie talkies with morse code keys for $2.99 in those stores. Not that they're worth that to begin with but then they'll sell you their batteries and whatever junk they try to attract your eyes with so they make a profit regardless. You might even be able to find them online for that price but shipping would kill the deal.

    TIP: When I see something cheap on Amazon with the "Super Savings Shipping" offered yet it's an inexpensive item I just add it to my cart and save it for later. Eventuially I'll need something over $25 or things will finally add up to that.