Wireless driveway alarm

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kenwn1
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Wireless driveway alarm

Post by kenwn1 » Tue Feb 24, 2004 7:54 pm

I recently purchased a wireless driveway alarm, but the range is too small. It sensor works only up to 200 ft. away from the house. I would like to place the sensor at the end of the driveway about 400 ft. from the house. Is there a way that I can modify the unit to accomplish this?

myp71
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Re: Wireless driveway alarm

Post by myp71 » Wed Feb 25, 2004 10:02 am

We would have to know more about it like how does it send (ie) R.F infra-red......?If it is R.F which I think it might be then you would prob have to know the frequency of the sending unit.Before you can add an I guess you would call a repeater type system where this thing sits between the sensor unit and the house alarm to boost the siginal of the sending sensor unit.

Tommy volts
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Re: Wireless driveway alarm

Post by Tommy volts » Wed Feb 25, 2004 10:26 am

I wish I had that problem (400 foot driveway).

kenwn1
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Re: Wireless driveway alarm

Post by kenwn1 » Wed Feb 25, 2004 11:55 am

Hi. Thanks for your reply. According to the information supplied with the unit, it transmits on a frequency of 434MHZ. The sensor is PIR (passive infrared). The sensor works great. My problem is trying to get the receiver in the house to pick up the 434MHZ signal more than 200 ft. away. This unit is advertised as a 400 ft range in open territory. I would have purchased a 1000 ft. unit but the price tag here in Canada is $349. compared to $99. for the 400 ft. unit. I didn't think that one should have to pay that much more for an extra 600 ft. of range.

perfectbite
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Re: Wireless driveway alarm

Post by perfectbite » Wed Feb 25, 2004 12:49 pm

It is entirely possible that at around 400 feet the IR signal is too weak to trigger the receiver. Try a focusing lens and sight it to the receiver. Use good batteries.

Will
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Re: Wireless driveway alarm

Post by Will » Wed Feb 25, 2004 1:08 pm

kenwn1 - I'm not a radio man but I have an inside/outside thermometer which accepts 433 MHz RF signals from a transmitter (Outside temperature) placed outside. It wouldn't work reliably from different positions outside of the house so I pinned a piece of wire 7 or 8 feet long to the ceiling above the receiver (A 7 ft long antenna) and placed the end of it just near to the receiver - in fact underneath it. Now it works perfectly. You could try that and, if it didn't work, try placing a small antenna outside your house and running a wire from there to the receiver.
What I would like to do if I were a radio man, is to construct a small simple 433 MHz receiver so that I could pick up the transmitter signal and feed it into my computer. Anyone got a design for such a receiver. If I had such I would put the output on to my scope and figure out what the numerical coding was.
BB

myp71
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Re: Wireless driveway alarm

Post by myp71 » Wed Feb 25, 2004 1:11 pm

And shouldn't IR be out of the direct sunlight?<p>I guess not cause at night it would reach Huh?<p> :confused:

perfectbite
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Re: Wireless driveway alarm

Post by perfectbite » Wed Feb 25, 2004 1:44 pm

I did a web search turned up what looked to be some very expensive IR camera lenses. Forget the lenses, think simple light beam. Experiment with the cardboard core of a roll of paper towels lined with Aluminum foil shiny side to the interior. If that works do the same with a piece of 3/4" Scedule 40 PVC water pipe and tie wrap it all together neatly. If it doesn't work try taping an old spectacle lens to the tube. Walking back and forth setting it up you'll get lots of exercise. You could connect the output to switch a lamp in the house on to tell you if it is working. I'm a widower so have to think how to do these 'around the corner or far away' things by myself. No more "Honey, Is it on yet? How about now? What do you mean it's smoking and sparks are coming out of it? Don't touch it"

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haklesup
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Re: Wireless driveway alarm

Post by haklesup » Wed Feb 25, 2004 1:45 pm

I gather proximity sensor is IR and the communication link to the base is RF.<p>You can try to improve the efficiency of the transmitter and/or reciever by modifying the antenna it uses. Try to find the antenna node on the PCB (it may be nothing more than a PCB trace or wire stub) and extend it with a wire or short rod antenna. Assuming that the 434MHZ is FM, this might work somewhat.<p>Similar to the above would be to get some coax cable and connect one end to the transmitter, reel out 200 feet and plant an antenna in range of the reciever. Kind of defeats the purpose of being wireless though.<p>A more direct solution would be to amplify the output of the transmitter directly. You would need to partially reverse engineer the circuit then design a transistor or op amp amplifier to boost the output power. Just a buffer for the output, not a whole transmitter (which is what a repeater would need). If this unit is battery powered. A booster could have a dramatic effect of battery life, you may have to add more cells to the transmitter.<p>Making the reciever more sensitive would probably be too difficult and may cause false triggering.<p>Any specific information about the manufacturer, a photo of the boards inside, a hand made schematic or listing of device part numbers could be helpful in giving further advice.<p>Any of the above solutions could be tricky when you consider transmission line reflections possible and the thought of putting an antenna of one impedance onto a circuit designed to drive a different impedance. Even if the final design is inefficient (WRT transmission power/radiation) if it works, who cares.<p>Chris

kenwn1
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Re: Wireless driveway alarm

Post by kenwn1 » Wed Feb 25, 2004 2:16 pm

The transmitter/receiver is RF. I took apart both units (both of which are battery powered) and the antenna in each unit is a length of wire 8 or 9 inches long and looped in a "U" around the perimeter of the plastic housing. The name on the unit is "Driveway Patrol". I have been thinking that either increasing the output of the transmitter or a directional antenna at the transmitter (to beam all the signal toward the house instead of it spreading out in all directions)to be the solution. Anyone have any ideas on a circuit design?

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Edd
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Re: Wireless driveway alarm

Post by Edd » Wed Feb 25, 2004 4:41 pm

Well just I was suspecting, before your last update info. A common PIR detector unit interfacing and feeding into a RF xmitter to link to its companion receiver and then provide your alarm notification of activity at the front of your property. Probably afar and possibly with view obstructed with shrubbery or trees. Also we can surely expect the PIR section functioning properly on detection of activity…except for stray wildlife…,with your only shortfall being the RF linking capability..specifically…the range.
Would this be your unit here ?:
http://www.alltvstuff.com/dwp1.html <p>At a whopping $19 USD low and upwards in pricing…… its for sure that the internal receiver technology is going to be a superregenerative receiver. Considering this and the info that you supplied on the RF carrier freq the units are utilizing a common folded dipole for T & R ant elements.
I don’t know how much you are up on RF technology but you would want to have both the Trans dipole(loop) and the Rec dipole aligned in the same X-Y plane to each other.
If that is fuzzy, I’ll give you a comparative mechanical analogy. Take two hula hoops and place them side to side and visualize a RF signal passing thru the center hole from one towards the other.if either, or both made a variance from that alignment there would be progressively less signal being coupled between the two with the most drastic attenuation if the loops were at a 90 degree offset.
That said, lets look at your transmitter units hook up. Having it up at a height of 10ft + is certainly where you would want it as compared to being down at the 3-5 ft level.
Height=range with RF. Next you don’t want the plastic Xmitter casing with its radiating loop clamped to a metal pole, that’s the potential of upsetting its internal dipoles radiation pattern or shielding off RF if the pole ends up being between the Xmitter-Rec path.
Considering that you now have the Xmit unit optimized within the above specifications and with its dipole oriented broadside towards your home/Receiver site, take the receiver outside to circumvent any metallic building wrap/foil sheathing
signal attenuation possibilities. Go to the side/corner of the house closest to the xmitter and then orient its loop likewise to the Xmitter. Evaluation time. If it doesn’t have proper range coverage, and ..IF..the receiver is battery powered ? can you walk up on the Xmitter and see at what point RF interconnect is established ?.
If you are still deficient on ranging I will next suggest an enhancemet of radiation efficiency on the Xmit-Rec dipoles by a test mockup utilizing parasitic directors in conjugation with the internal circuitry dipoles. An initial evaluation mockup would only entail the use of a cardboard support plane taped to the Xmit casing with ¼ width aluminum foil strips trimmed 10% shorter than the dipole you measured and about 5 of them spaced on out at .15 λ and that derived Yagis parasitic elements would then be oriented towards direction of the Rec. If that would still be deficient the same procedure could be done at the Rec end.
For the time being though, give the findings on the initial info.<p>PS.. a pine forest between the two sites is not good info either.<p>An ASIDE for Will:
A simple RF sniffer with an 1N34 at your scope probes tip and placed up near the Temp sensor units RF section will enable a viewing of your data streams coding information.<p>[email protected] .........(Interstellar~~~~Warp~~~Speed)
[email protected].........(Firewalled-Spam*Cookies*Crumbs)
;) ;)<p>[ February 25, 2004: Message edited by: Edd Whatley ]</p>

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Chris Smith
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Re: Wireless driveway alarm

Post by Chris Smith » Wed Feb 25, 2004 5:21 pm

Add a simple microwave transistor to the out put stage. <p>Four wires only,..... one for in, one for out, and two for power and ground. <p>This should boost the out put about ten fold? <p> However, if the FCC comes a knocking, don’t say I did it? <p>You will probably need a resistor divider to set the input voltage only?

myp71
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Re: Wireless driveway alarm

Post by myp71 » Wed Feb 25, 2004 6:50 pm

Ok a wire for the antenna I though it was a IR LED.

perfectbite
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Re: Wireless driveway alarm

Post by perfectbite » Wed Feb 25, 2004 10:44 pm

'Curses' foiled again. I was convinced the whole set up was IR. How would line of sight work in the snow banks anywhere in Canada anyway? I will read more carefully next time.

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jwax
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Re: Wireless driveway alarm

Post by jwax » Thu Feb 26, 2004 4:44 pm

$349 Canadian for the 1000 ft unit?
I'll build and sell you the same thing for half of that! How many do you want to order? :D

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