Picture of PetSafe Pet Barrier Transmitter

Most pet owners are familiar with the concept of a wireless pet containment system: the animal wears a "shock" collar; when the animal is too near an antenna of a transmitter, the animal gets warned with a vibration or beep, then shocked. Typically, the antenna to the transmitter outlines the perimeter of a yard --- an underground fence. If a pet owner also wants to keep an animal out of a certain area in the house, perhaps off a piece of furniture, they can buy an indoor transmitter as well. However, most pet owners do not do this:
1. The transmitter is expensive
2. The circular pattern of transmission for the indoor transmitter is often not appropriate for the area of containment. How would you use one transmitter to keep an animal off a couch while allowing them around the couch, for example?
3. The thing is big, ugly, and in the way. Where can you put it that will be convenient for you and still will outline the area of containment?

Ready for some good news? We can make our own transmitter, completely compatible with PetSafe collars but smaller than PetSafe's, with an antenna that can be any shape or size, for under $5! Our transmitter can serve as a replacement for an outdoor or an indoor system. And if you are ready for a break from the Arduino and friends I have more good news: we don't need a microcontroller. This can all be done with a couple of 555 timer ICs (available literally everywhere, including Radio Shack, Jameco, and All Electronics) and some supporting passive components. There's no code to write. You can build this thing without ever going near your computer (assuming you have a way to read this and surf the web without a computer.) And you can have the satisfaction of knowing you built the magical transmitter yourself.

nate64726 months ago
can I have this made for me?
Misant7771 year ago

Hey guys,

This is a great project and I really like the arduino approach also, but I'm wondering: If I'm wanting to run this through about 1,000 feet of 20 gauge solid core wire, will I have to build an amplifier, or should it be ok on it's own?

If I need to build an amp, would a 2n2222 common emitter transistor amp like this one work?


Or would I need something more along the lines of a fast power transistor?

is there any chance anyone knows how PetSafe's "YardMax" system
functions? If the dog runs through the boundary, it continues the
correction for a short period of time, or until the dog returns to the
safe area. Is this a change in collar design only, or is the transmitter
also different?

I would just up the voltage on your loop. Since the added length of wire is just like adding an extra resistance in series, I should thing raising the voltage to 9 or 12VDC should do a lot to enhance the signal. See my additional uploads which include a simple circuiit diagram and another photo of my arduino version of this project.

I have since created my own instructable showing this circuit:


crazy1gadgets made it!1 year ago

Ok, here it is. I wired up an arduino with the output NPN power transistor on pin 9, just as if I were wiring up a basic LED blinking circuit, then wired a 100 ohm resistor in parallel with the output load wire loop. Powered with a 9V battery.

I used the arduino timer1.pwm routine to generate the 10.5KHz durin the onpulse, and a loop with 18ms on / 18ms off for the 36 ms pulse carrier wave. This emulates the astable multivibrator circuit you created with your 555 circuit.

Here is the code:


* Astable multivibrator signal emulator

* for PetSafe fence


#include "TimerOne.h"

void setup()


pinMode(9, OUTPUT);

Timer1.initialize(95.2); // initialize timer1, and set a 95.2us second period (10.5KHz)


// the loop routine runs over and over again forever:

void loop()


Timer1.pwm(9, 512); // setup pwm on pin 9, 50% duty cycle

delay(18); // wait for 18ms

digitalWrite(9, LOW); // turn the LED off by making the voltage LOW

delay(18); // wait for 18ms


2014-04-17 12.49.00.jpg2014-04-17 12.49.07.jpg

What type/model transistor have you used in this? I would like to replicate but not too sure. I have the arduino and your part seems a lot easier than me cobbling together the 555 circuits above.

whyameye (author)  crazy1gadgets1 year ago
Fantastic! You beat me to it! I'll be duplicating your setup soon. Wonderful news that it seems to work so well. I appreciate your comment letting me know and sharing the code.
whyameye (author)  whyameye1 year ago

I'm curious if you tried leaving out the NPN. My guess is that the pin doesn't offer enough current without it?

Yes, it does work, and just as well. I measure about 9mA, well within the pin 9 current limit of 20mA. (FYI, I wired the 100 ohm resistor in series with the wire loop, not parallel - my error). However, I like to be safe and source resistive loads with an external power transistor. If I am running the thing all night, I would rather dissipate heat through the external transistor than the arduino board.

I don't have time to delve into this project too much. If you want to take the reigns on this and research/develop the arduino version more, it would make a good part II to your excellent instructable page.

A follow up. I got the PetSafe receiver device and wired up and arduino to perform the signal pulse you described. It works wonderfully! I will follow up with more detals soon. Thanks again for your fantastic instructable post.

I have a cat which I want to keep off our kitchen counter. This seems like a great idea. I should think this would work with the PetSafe cat receiver collars as well? What about other brands, such as Innotek?

I should think that with some tweaking, one could get it to work, what do you think. I am an engineer, so I am familiar with electronics and am pretty sure I have the parts and equipment in my shop to make this.

whyameye (author)  crazy1gadgets1 year ago

I'm only familiar with the PetSafe dog collars so I can't answer anything definitively, but I agree with you that it will likely work with the cat collars and with other brands, perhaps tweaking the frequency and the timing between the bursts. If it were me, I'd play with the Pd patch I provide to confirm all the settings, then build the circuit tweaked for those settings.

Arduino clones are so cheap now --- it seems easiest and more robust to perhaps build the transmitter with one of those instead of the circuit I outline. I'll be trying that within the next few weeks and let you know how it goes.

BTW if your cat gets on the counter only when you aren't home/around, you might just connect a motion sensor to an alarm.

Thanks for your quick reply. I have ordered the PetSafe Cat collar online and will be testing it with an Arduino PWM circuit as you suggested. I have a 'scope so I will be able to tweak it to spec pretty easily, I think.

I had thought about the motion sensor, but the cat still does jump on the counter when we are around (albeit less than when not around, i am sure). I also wanted to try something a bit more localized, as the counter stretches around corners and into the other room. I may yet do a motion control sensor in conjunction with the wired "fence" to see if that works better. I will keep you posted.

hi just wondering if this could be used as a garden fence solution? Many thanks

whyameye (author)  gabrieldillon1 year ago

Seems like it could work as a garden fence solution. If you try it, let us know and post your results! :-)

I don't need one myself, but may I say BRAVO.
The genius is in the simplicity.
Yes of course some ATmega 8 pin microcontroller could do this without frequency drift, but they didn't give you one! LOL! The concept implementation was great given what you had to work with though. Good thing you had more than one 555 !.
HelmutHound2 years ago
Very nice ible! What programs and applications did you use for this? (I especially like the signal / wave form displays, and the circuit board blueprint)
whyameye (author)  HelmutHound2 years ago
Circuit board and Schematic are screen shots from the free version of Eagle. I inverted the colors and flipped the image with Gimp. Wave form displays are just pics from my phone of an oscilloscope. Glad you liked the idle!