RF receiver at detecting drop in signal at specific range

Pyro Project Ideas/Requests
SereMaddox
Newbie Pyro
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Joined: Thu Oct 11, 2012 5:54 pm

RF receiver at detecting drop in signal at specific range

Postby SereMaddox » Thu Oct 11, 2012 6:08 pm

Hi. I've been trying to design a wireless dog leash using an "always on" key-fob transmitter, but am really REALLY new to designing circuits, so would you be able to tell me what I'd need for (or how I'd need to make) a circuit that does not switch on until the signal detection falls below a certain threshold?

Like I said, this is for a wireless dog leash, because I'm always getting leashes wrapped around poles or cars or other folks and if my pet was wearing the receiver on their harness that either made a high pitched sound only they could hear or gave a little shock or spritzed citronella at them or something, if they got too far away from the transmitter, (say 30 feet or so, but I suppose that dialing the transmission power up or down would "lengthen or shorten the leash"), then that solve the problem.

OK, if she decided to take off like a bat out of hell after a squirrel or something, this would be less than adequate, but she's pretty well behaved, so I'm not worried about this particular instance where a physical leash would be far superior.

Thank you very much - a pleasure to be on your forums.

~Sere

ThePyroElectro
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Re: RF receiver at detecting drop in signal at specific rang

Postby ThePyroElectro » Thu Oct 11, 2012 11:07 pm

SereMaddox wrote:Hi. I've been trying to design a wireless dog leash using an "always on" key-fob transmitter, but am really REALLY new to designing circuits, so would you be able to tell me what I'd need for (or how I'd need to make) a circuit that does not switch on until the signal detection falls below a certain threshold?

Like I said, this is for a wireless dog leash, because I'm always getting leashes wrapped around poles or cars or other folks and if my pet was wearing the receiver on their harness that either made a high pitched sound only they could hear or gave a little shock or spritzed citronella at them or something, if they got too far away from the transmitter, (say 30 feet or so, but I suppose that dialing the transmission power up or down would "lengthen or shorten the leash"), then that solve the problem.

OK, if she decided to take off like a bat out of hell after a squirrel or something, this would be less than adequate, but she's pretty well behaved, so I'm not worried about this particular instance where a physical leash would be far superior.

Thank you very much - a pleasure to be on your forums.

~Sere


Hello,

The easiest solution I see to this problem is to use a comparator on your receiver and to set a known [voltage/current/power] as your threshold. Once the received, filtered and amplified signal passes that threshold you can activate whatever additional circuitry on the receiver you desire.

Basically, your transmitter will have a stable output power that should not vary much unless your batteries start dying. As your receiver gets further and further away, the power transmission of your signal from transmitter to receiver becomes less and less. And at your pre-determined comparator point the receiver can activate that additional circuitry.

The main issue I see here is it will be incredibly hard to calibrate this circuit for all enviornments. Something as simple as a person walking between you and your dog could create significant power loss in your transmission, and it would seem like the modules are far away from each other when in reality you're the same distance away from your dog that you were a minute ago.

I would suggest an alternate approach to solving your problem: instead of having the transmitter always on, you control the transmitter and actively decide when the receiver's additional 'dog training' circuitry is triggered by turning on the transmitter (push button or switch). This would remove any (distance) calibration need and would be generally a more reliable system. Additionally, I think there are products that do this on the market already....no matter, just thought I'd mention it.

Feel free to let me know what you think.


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