Hi,
I am not an electronics expert by any means but I have an idea which
might work and wondered what you all thought of it.
My problem is that I have been threatened by various people for various
reasons. We don't need to go into the whole story right now. Suffice to
say, I have reason to fear certain individuals (whose barks are
probably worse than their bites) and have been thinking of ways to
protect myself, my family and my property from them.
Whilst I have an alarm system in my house, it only goes off after
someone arrives and that doesn't give me any time to prepare. What I'd
like is some sort of early warning system to inform me when they are on
the way. The geography of the area dictates that they have to drive
down a specific road, over a mountain, to get to me.
I know their vehicles and was thinking about placing some sort of radio
transmitter on each one. Maybe I could have a receiver, tuned to the
correct frequency, permanently switched on at my house. This would
presumably start making a noise once one of the transmitters came into
range.
There are several problems with this approach: to be any use, the
transmitters would need to work over a range of at least 20-30 Km. My
guess is that would make them bulky, expensive and energy-hungry.
Whilst I may get away with placing a transmitter once, I don't relish
the idea of going back to change the batteries every month! Whatever
solution I implement, the power should last as long as possible - more
than a year would be good. I thought about hooking into the vehicle's
batteries, but that would take too long to install. I need something I
can quickly stick under a wheel arch or bumper. And whatever I stick
there must be cheap, so cheap that it is virtually disposable. I want
to stick 10-20 of them onto various vehicles without breaking the bank.
Ideally, they should cost less than US$5 each. Finally, they should be
highly robust. Being stuck under a car, they will need to survive rain,
dirt, heat and vibration.
All that got me thinking about using RFID transducers. They are cheap,
long-lasting and very robust. The obvious problem is that they are
low-range. As I understand it, the maximum range of a battery-powered
UHF transducer is around 100 metres - not long enough to give me
sufficient warning, but this isn't necessarily a problem...
As I mentioned before, there is really only one road to my house. My
idea is to install some sort of receiver unit at the side of this road.
This would be triggered whenever one of the RFID units comes into
range. This still leaves the problem of how to inform me, 30 km away,
that the unit has been triggered. I have two possible solutions:
The first method is to use a second, higher-powered, radio transmitter
to send me a signal. It wouldn't matter if this one was bulky and
energy-hungry because it would be fixed in place on a lamp post by the
side of the road, probably with a mains electricity supply (although
that may not be easy). I could probably arrange it so that this
transmitter (or its antenna) has a clear line of sight to a receiver
antenna on top of my house. This is helped by the fact that the road
goes over a mountain. All I need is some sort of switch that responds
to a passing RFID transducer by activating this transmitter. Ideally,
to avoid false alarms, this would only happen if the RFID transducer
belongs to a limited set of ID numbers - although I doubt there will be
many false alarms for the foreseeable future. I would need some sort of
receiver to sound the alarm at my home. This would need to make a noise
continuously until it is switched off, a bit like a normal burglar
alarm.
The second method is to use a mobile phone to alert me. Ideally. it
would send an SMS (or several to various numbers) and/or call me and
keep calling me until I answer. A possible benefit of using a mobile
phone is that, if I use one with a built-in camera, I could also take
some photos and send them via MMS along with the SMS warning message.
That would be great. Not only would I have a 30-minute warning of
impending trouble, I would also have photos showing me how many bad
guys to expect. Plus, I would receive the warning wherever I happened
to be.
My guess is that I could maybe connect an RFID reader to a PDA - which
is programmed to send SMS messages/make calls via a connected (or
built-in) mobile phone. This seems reasonably do-able, but I have no
idea how to go about it. I have a programming background, but not in
this kind of thing. I wouldn't even know what language to use. I'm also
a bit reluctant to risk losing an expensive PDA in this way (but
recognise that it may be a necessary risk and realise I could probably
use a second-hand one).
Whichever method I use, I imagine the receiver unit could be housed
inside a waterproof container and secured to a lamp post or similar -
which would help with night photos!
One problem is how to power the device. The obvious solution would be
to use batteries, but I don't want to have to change them every few
days. Once a month is OK, but any more than that and it's gonna get
tedious. Also, people are going to start wondering what I'm doing.
I thought about using a solar panel, but I'm not sure. I imagine they
are quite expensive (remember, it could be stolen) but I'm open to
suggestions.
I *may* be able to gain access to mains electricity at the roadside. If
so, it would be prudent to assume that this could be cut off at any
time. So, ideally, the unit would run on batteries, but would use mains
power to charge up from time to time. It would be great to receive a
warning if the mains power is cut or if the battery gets low.
That's about it. In summary, I need someone to help me design a
roadside early warning system that is triggered by the presence of an
RFID chip (or similar small, cheap, robust and energy-friendly
transmitter). I should be able to place a number of these transmitters
under car bumpers or wheel arches. The receiver unit should either
transmit a warning signal or send an SMS to my mobile phone, and maybe
others, whenever it is triggered. Ideally, it would also be able to
send a series of photos by MMS. It should run on batteries, but with a
method for topping up from the mains and, ideally, calling for help if
it runs into energy problems.
What do you reckon? Is this feasible? Does anyone have any advice about
how to implement it in practice? I'd really appreciate your thoughts,
ideas, suggestions and recommendations.
I am not an electronics expert by any means but I have an idea which
might work and wondered what you all thought of it.
My problem is that I have been threatened by various people for various
reasons. We don't need to go into the whole story right now. Suffice to
say, I have reason to fear certain individuals (whose barks are
probably worse than their bites) and have been thinking of ways to
protect myself, my family and my property from them.
Whilst I have an alarm system in my house, it only goes off after
someone arrives and that doesn't give me any time to prepare. What I'd
like is some sort of early warning system to inform me when they are on
the way. The geography of the area dictates that they have to drive
down a specific road, over a mountain, to get to me.
I know their vehicles and was thinking about placing some sort of radio
transmitter on each one. Maybe I could have a receiver, tuned to the
correct frequency, permanently switched on at my house. This would
presumably start making a noise once one of the transmitters came into
range.
There are several problems with this approach: to be any use, the
transmitters would need to work over a range of at least 20-30 Km. My
guess is that would make them bulky, expensive and energy-hungry.
Whilst I may get away with placing a transmitter once, I don't relish
the idea of going back to change the batteries every month! Whatever
solution I implement, the power should last as long as possible - more
than a year would be good. I thought about hooking into the vehicle's
batteries, but that would take too long to install. I need something I
can quickly stick under a wheel arch or bumper. And whatever I stick
there must be cheap, so cheap that it is virtually disposable. I want
to stick 10-20 of them onto various vehicles without breaking the bank.
Ideally, they should cost less than US$5 each. Finally, they should be
highly robust. Being stuck under a car, they will need to survive rain,
dirt, heat and vibration.
All that got me thinking about using RFID transducers. They are cheap,
long-lasting and very robust. The obvious problem is that they are
low-range. As I understand it, the maximum range of a battery-powered
UHF transducer is around 100 metres - not long enough to give me
sufficient warning, but this isn't necessarily a problem...
As I mentioned before, there is really only one road to my house. My
idea is to install some sort of receiver unit at the side of this road.
This would be triggered whenever one of the RFID units comes into
range. This still leaves the problem of how to inform me, 30 km away,
that the unit has been triggered. I have two possible solutions:
The first method is to use a second, higher-powered, radio transmitter
to send me a signal. It wouldn't matter if this one was bulky and
energy-hungry because it would be fixed in place on a lamp post by the
side of the road, probably with a mains electricity supply (although
that may not be easy). I could probably arrange it so that this
transmitter (or its antenna) has a clear line of sight to a receiver
antenna on top of my house. This is helped by the fact that the road
goes over a mountain. All I need is some sort of switch that responds
to a passing RFID transducer by activating this transmitter. Ideally,
to avoid false alarms, this would only happen if the RFID transducer
belongs to a limited set of ID numbers - although I doubt there will be
many false alarms for the foreseeable future. I would need some sort of
receiver to sound the alarm at my home. This would need to make a noise
continuously until it is switched off, a bit like a normal burglar
alarm.
The second method is to use a mobile phone to alert me. Ideally. it
would send an SMS (or several to various numbers) and/or call me and
keep calling me until I answer. A possible benefit of using a mobile
phone is that, if I use one with a built-in camera, I could also take
some photos and send them via MMS along with the SMS warning message.
That would be great. Not only would I have a 30-minute warning of
impending trouble, I would also have photos showing me how many bad
guys to expect. Plus, I would receive the warning wherever I happened
to be.
My guess is that I could maybe connect an RFID reader to a PDA - which
is programmed to send SMS messages/make calls via a connected (or
built-in) mobile phone. This seems reasonably do-able, but I have no
idea how to go about it. I have a programming background, but not in
this kind of thing. I wouldn't even know what language to use. I'm also
a bit reluctant to risk losing an expensive PDA in this way (but
recognise that it may be a necessary risk and realise I could probably
use a second-hand one).
Whichever method I use, I imagine the receiver unit could be housed
inside a waterproof container and secured to a lamp post or similar -
which would help with night photos!
One problem is how to power the device. The obvious solution would be
to use batteries, but I don't want to have to change them every few
days. Once a month is OK, but any more than that and it's gonna get
tedious. Also, people are going to start wondering what I'm doing.
I thought about using a solar panel, but I'm not sure. I imagine they
are quite expensive (remember, it could be stolen) but I'm open to
suggestions.
I *may* be able to gain access to mains electricity at the roadside. If
so, it would be prudent to assume that this could be cut off at any
time. So, ideally, the unit would run on batteries, but would use mains
power to charge up from time to time. It would be great to receive a
warning if the mains power is cut or if the battery gets low.
That's about it. In summary, I need someone to help me design a
roadside early warning system that is triggered by the presence of an
RFID chip (or similar small, cheap, robust and energy-friendly
transmitter). I should be able to place a number of these transmitters
under car bumpers or wheel arches. The receiver unit should either
transmit a warning signal or send an SMS to my mobile phone, and maybe
others, whenever it is triggered. Ideally, it would also be able to
send a series of photos by MMS. It should run on batteries, but with a
method for topping up from the mains and, ideally, calling for help if
it runs into energy problems.
What do you reckon? Is this feasible? Does anyone have any advice about
how to implement it in practice? I'd really appreciate your thoughts,
ideas, suggestions and recommendations.
