Instructables
This project uses an RF receiver module to trigger a pulsing LED Heart when the transmitter comes within range. I made this for my fiance for Valentine's Day this year.



I have yet to fully test the range, as I haven't actually taken the transmitter out of our apartment building since I just finished it today. The transmitter/receiver pair that I used is hypothetically capable of up to 500 feet, though that is the open space line of sight range. I haven't yet added antennas to either the receiver or transmitter box, but that should hypothetically improve the current range.
phd.WMV419 KB
 
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Step 1: Tools and Supplies

Tools Needed:

Soldering Iron
Dremel
Drill (or fairly large drill bit for the Dremel)
Screwdriver

Supplies
2 LEDs (1 red for the heart, another any color for a power light for the transmitter)
Printed Circuit Board (I used 276-159 from RadioShack)
2 5v Voltage Regulators (7805 or similar)
2 9v batteries
2 9v battery clips
2 project boxes (I used 270-1803 for the receiver, and a small 3x2x1 or so box for the transmitter)
2 SPST switches (I used 275-645)
2 8 pin DIP sockets (I used 276-1995)
2 PIC 12f683 (you can get a few of these as a free sample from Microchip)
2 Resistors (value depends on the LEDs you use, somewhere around 100ohms for typical LEDs from the 5v regulated voltage)
A small piece of plastic (preferably cloudy, or translucent)
wire
and last but most importantly
RF transmitter and receiver (I used RF-KLP-434 from Sparkfun, which was 11.95 for the pair)
It makes me wonder how compact you could make this. It'd be great to wire into remotes, cameras, etc, with a very short range to use as a detector for when you lose that kinda stuff.
Could I use this to detect other rf frequency devices (like cameras or bugs or hidden cctvs)?
daenris (author)  Lithium Rain6 years ago
Not really. You could potentially use the receiver chip to detect frequencies within the range of the receiver (434mhz). Most devices like you mention (cameras, bugs, wireless video) work on much higher frequencies.
lol.... its probably my negative, untrusting mind working....... but its like a last stage emergency hide in the closet cheater alarm....lol. nice idea though
Perhaps I am just as bitter as you are, but that is EXACTLY what I was thinking. I would actually be offended and puzzled by receiving a gift like this.
Oops, still good instructable and interesting project for OTHER uses.
turgan7 years ago
wow. this is a fantastic project. i'm going to go ahead and ask it: can a non-programmer geek be able to overcome this project?
zaydenam turgan7 years ago
Yeah, If you only want to make the LED pulse you can do it with a really simple 555 astable circuit. Google it find out about its schematic and formula (real simple 3rd grade stuff) and connect the output you get from your 555 oscillator to the transmitter input) And if you can just connect a 5volt supply directly to the transmitter input if you don't want a pulse. However if you want to send seial data you'll have to use a micrcontroller with SCI or if you don't want to use a microcontroller you can use the D3-6402-9 UART. Its obsolete but you can still get it from the net. Its what i'm using for my sign language glove science project at my school.
marcss zaydenam6 years ago
I may be alone here, but that sounded more like a "No," than a "Yes." =)
daenris (author)  zaydenam7 years ago
That actually won't work. I tried it, and even with a pulsing input, the output just kinda flashes. The pulsing needs to be at the output. So hypothetically you could put a 555 timer on the transmitter to create a blinking effect, and on the output put a 555 timer on the receiver to create a pulse when there's a signal received.
If you put a capacitor across the clock pin on the 555 and ground, it might work!
Yeah if it doesn't work like that. That's a good alternative. But why would you want a 555 on the transmitter just connect directly to supply so it always transmits in range and use the reciever output to drive a 555 oscillator.
daenris (author)  zaydenam7 years ago
The receiver tends to attenuate when it receives a constant signal, so it would eventually end up losing the signal. In order to prevent that it needs a changing signal received, so you need to turn the transmitting on and off.
can i get an approximation on price
daenris (author)  Sir No Pants6 years ago
I don't have an exact breakdown by parts, but overall it was under $30. The RF transmitter/receiver were the most expensive item at around $12 (although now it looks like they're $14 from SparkFun). The project boxes were a couple of dollars each. The PICs I actually got free as a sample from Microchip, but they're likely a dollar or two from Digikey or Mouser. Any switch can be used for about $1-2. Beyond that most of the stuff was very cheap, you can get a bunch of resistors for a couple bucks and you only need two. The voltage regulators are around $1. The LEDs are cheap (again you can get a bunch for a $1 or 2). The battery, clips, and sockets are under $1 each.
sabeen5576 years ago
I should make one. Plant the transmitter in my boss' truck. Really good instructable.
jarv347 years ago
nice! have you measured the power consumption to estimate your battery life on a single 9v?
daenris (author)  jarv347 years ago
Not yet. If I get a chance I'll pull them open and check.
Would it be possible for you to provide some schematics for the transmitter and receiver? Thankyou
daenris (author)  macmaniac7 years ago
Yeah. It's pretty straightforward, but I'll add them tonight if I get a chance.
Duardo7 years ago
I love your project, nicely done. Could you tell me which compiler and PIC programmer you used. I've been looking for a free C compiler and haven't found one yet. Thanks.
Duardo Duardo7 years ago
Thank you for your prompt and very useful reply.
daenris (author)  Duardo7 years ago
The programmer I used was a homemade version of the RCD Programmer (http://feng3.cool.ne.jp/en/rcd.html).

The compiler I used was the CCS PIC C compiler, which is not free. There are free versions of many C compilers for PICs, though they usually have some limitations in the size of the code or the types of PICs they can program. SDCC is an experimental open source compiler, and there are some (HITECH, CC5X, BoostC) that offer free versions.

This post (http://forum.sparkfun.com/viewtopic.php?t=1039) on the SparkFun forums discusses many C compilers for PICs.
Proteus7 years ago
Very Nice Project! I've just finished a project using a similar PIC , It's a nice idea to set the PIC to sleep on those 500ms (use WDT to wake up) and also kill the power to the receiver while pic is sleeping (transistor) so that the battery can last longer (I'll post my project soon (also used picc) , it involves a LED but I'm using an ActiveCapacitiveSensor which also drains power...)
daenris (author)  Proteus7 years ago
That is a good idea. I'm relatively new to PIC programming, so I'll have to look into how to setup the sleep/watchdog to control it.
Proteus daenris7 years ago
This is the project I was talking about, nice use for WDT :
http://www.instructables.com/id/E2HI3MXWXWEXCFM05H/
daenris (author)  Proteus7 years ago
Very nice. Since I'm just starting out with PICs the code is very helpful. A lot of the sample code I find is in assembly, which I'm sure I'll eventually have to get a handle on, but I'm a C/C++ software person, and it's harder to find good examples in C. Also really nice that you have the whole circuit in a single socket.
technick297 years ago
Wow, this is one hardcore idea! I like it a lot, and I think I'll try making this sometime. Very thorough Instructable also! All around, good job.
daenris (author)  technick297 years ago
Thanks. I figured I'd better make my first one good :)