I'm working on a project that requires me to build an antenna and I'm not very experienced with wireless transmission. Here is an overview of my project: Four parking spots for cars with pressure plates that produce roughly 4 or 5 volts when a car is parked in a spot. (this is small scale - think model car size) Since the 4 volts indicate that a car is parked, we want to send that signal to the entrance of the parking lot that lights up an LED indicating the spot is taken. The distance between each spot and the entrance would be roughly 3 feet max. There would be a LED for each spot

We were thinking of using an oscillator to convert the voltage to a signal that can be transmitted through an antenna. Something like this: https://www.sparkfun.com/products/9089 I did more research and found this chip that supposedly converts voltage to frequency and frequency to voltage which would be perfect for this project (again, I'm not experienced with wireless transmission - this could be wishful thinking) We wanted to use a microchip antenna so we can solder on a PCB. Here's an antenna example: https://www.sparkfun.com/products/144 So would we need a receiving antenna with the same Hz as the transmitting antenna? I'm assuming I could solder the receiving antenna to the frequency input, or is that completely wrong? I assume we would need a different frequency for each parking spot sensor so the corresponding LED would light up. Does that sound correct?

My main questions if you guys can't answer the few in the paragraph before is this:

  • What antenna (or antennas if I need multiple ones) would I look for to transmit the converted voltage/frequency

  • Would I need extra parts to help transmit the frequency and receive it?

Thank you for your patience and your expertise, every bit of knowledge helps and I appreciate any input. Thank you!

  • \$\begingroup\$ The antenna will be based on the frequency and ERP requirements. You want to use a carrier signal with different frequencies for each parking spot!? Did you know the major bands are licensed right? Or you want to modulate the carrier frequency with another one, like FM? \$\endgroup\$ Jan 24, 2014 at 18:12
  • \$\begingroup\$ Doing it yourself will first require you to learn a vast amount. There are much easier ways. You can buy modules that allow you to apply a voltage at one end and receive a "contact closure" or voltage at the other. Some can be preset to serve a large number of possible channels. \$\endgroup\$
    – Russell McMahon
    Jan 25, 2014 at 11:25

1 Answer 1


The oscillator modules from Sparkfun you are linking to are not meant for RF transmission. You need a transmitter/receiver pair for each parking spot, assuming you are mimicking a system that would have distances of more than 3 feet. A Sparkfun module that you might look at is: RF Link Transmitter - 434MHz WRL-10534. In a simple minded system you could use transmitter/receiver pairs with four different frequencies. If all there spots were close to each other but far from the entrance, you could use one transmitter/receiver pair with different codes for the spots.

In the title of the question you use the phrase "power multiple LEDs". I assume you are not literally powering the LEDs, but signaling them.

For the very short distance in your model, I do not think much of an antenna would be needed.

  • \$\begingroup\$ Thank you for your comment, it's very helpful! If the oscillator is not a good choice for RF transmission, should I search for an ADC or do you have any suggestions to just convert a high low signal without a microcontroller? Thanks again. \$\endgroup\$
    – user35653
    Jan 25, 2014 at 15:59
  • \$\begingroup\$ If the signal for car present is a clear on/off there is no need for an ADC or a microcontroller. The very simplest set up that might work is to connect the car present signal to the data in pin of the transmitter. At the receiver end you might use a one transistor circuit to take the digital out signal and control the LED. The most you should need to add to that would be a comparator to detect the voltage input and an inverter if the sense of things would have the LED off/on reversed. \$\endgroup\$ Jan 25, 2014 at 21:28
  • \$\begingroup\$ I checked my force sensor and it actually gives off a 4-5 Volts when an object is placed on it. I guess I was thinking On - 4 Volts, Off - 0V. Thanks for the feedback! \$\endgroup\$
    – user35653
    Jan 26, 2014 at 3:08

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