Driveway alert monitor help w/pics

[Carl6405]

Hey folks. This is my first post here, but not new to diy forums. I am very happy to find an electronics forum.

Ok, so, heres the deal. I have owned this driveway alert system now for a couple of years. It has been a great system when it works. Several months ago, it became unreliable. What I found is that the transmitter is working fine. I verify the transmitter is working, by tuning in my police scanner to the frequency of 433.9125mhz and everytime the transmitter senses motion, it transmits. Now, the receiver, is where the issue is. I had replaced the internal antenna with a simple piece of solid copper wire, and solderd it to the circuit board, next to the DR1 433B chip. Not sure what "DR" means.
That worked for a while, but got to be just as bad, and the range( transmitter to receiver) is supposed to be several hundred feet, became, a few steps away. So, Im thinking that I may have damaged, by soldering to much, the DR1 433B component. Now, the receiver is not picking up on the signal from the transmitter at all.

I would like suggestions on this. I would like to fix this board or build another simple receiver that will pick up on this signal, 433.9125Mhz and trigger an audible alarm that would alert us, essentially replacing the receiver part of the system.

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[mneary]

It would seem that the vulnerable part is a SAW filter, but I wouldn't suspect at first look that it's damaged.

More likely it's just a solder bridge under or around the part. I suggest you find someone experienced in SMT soldering and have them clean it up. If you want to give it a go, start with some fine Solder Wick to remove the excess solder.

 

[Carl6405]

Sure, thanks for the tip. My soldering tips are all worn and need replacing. I have solder wick as well and will try that. This component got like this from me trying to improve the range. I have plenty of UHF rubber antenna's on hand and was trying to make one of those work. Also, I have found these 433.92mhz receiver modules, **broken link removed** and was wondering if I could build a receiver kit out of this compnent.

 

[BrownOut]

I can't help debug it. But I think the way you tested the transmitter was very resourceful

 

[Carl6405]

Thanks, yes that scanner picks it up every time. I would like to build a simple receiver / audio alert circuit that can pick up that frequency. I found a "RX433B: 433.92 MHz Receiver Module" at an electronics site for $9. The spec's are
Specifications
Frequency Range : 433.92MHz
Supply Voltage: 4.5~5.5V
Selectivity: -116dB
Data Rate: 4800bps
Current: 7.5mA!S0.5mA(DC/5V)
Circuit Shape: S/R+S/F
Modulate Mode: ASK
High sensitivity passive design.
Simple to apply with low external count.

Applications
Wireless security systems
Car alarms
Remote gate controls
Remote sensing
Date communication
Remote water/electric switch
Pager system
PDA data communicated

Im wondering if anyone here has any experieince with building a RF circuit for something like this.