Ok so based on the circuit i posted, on your pcb the chip U3 pins 1&7 are the outputs measure the DC voltage on these pins without waving your hand, then wave your hand and see which pin stays high or low (at the same time the led should be on ) that pin will trigger the TX chip, so you could put the tilt switch in place of this .

 

Ok so based on the circuit i posted, on your pcb the chip U3 pins 1&7 are the outputs measure the DC voltage on these pins without waving your hand, then wave your hand and see which pin stays high or low (at the same time the led should be on ) that pin will trigger the TX chip, so you could put the tilt switch in place of this .

Here's what I determined on the U3 chip, considering pins numbered 1 through 8 with one at upper left corner and going counter-clockwise from there. Pin 1, no voltage either way. Pins 2 and 3, no voltage without motion, but 3.3 when LED is on. Pin 4, nothing. Pin 5, 3.3 volts either way. Pin 6, .6 volts either way. Pin 7, 3.3 volts either way. Pin 8, 3.3 volts no motion and 1.3 volts when motion detected. Interesting, no?

 

OK, given this additional information, here is a simple, easy, optically isolated, and totally reversable, noise-immune scheme for generating a trigger signal from the tilt sensor.. Add an infr-red LED and a series resistor to limit the LED current to just a few milliamps.. The LED will nee to be located so that some IR illuminates the PIR sensor. This should generate a trigger and send the signal. And the addition circuit will not need to be shielded because it will be quite isolated from the analog circuitry. Contact bounce in the tilt switch will be a benefit, generating a more solid trigger. And no risk of soldering the wrong connection on the circuit board at all.

 

OK, given this additional information, here is a simple, easy, optically isolated, and totally reversable, noise-immune scheme for generating a trigger signal from the tilt sensor.. Add an infr-red LED and a series resistor to limit the LED current to just a few milliamps.. The LED will nee to be located so that some IR illuminates the PIR sensor. This should generate a trigger and send the signal. And the addition circuit will not need to be shielded because it will be quite isolated from the analog circuitry. Contact bounce in the tilt switch will be a benefit, generating a more solid trigger. And no risk of soldering the wrong connection on the circuit board at all.

That sounds like a great idea, I think it will work. I'll need to order the LED, none available locally, but no problem there. Am I understanding correctly that the LED would run directly off the 9V battery with the series resistor (what rating should that be?) in between? The tilt switch would go between the + battery terminal and the resistor? A simple diagram would be great if possible, as you can tell I'm not an electronics expert (actually retired electrical contractor with a great INTEREST in electronics! Thank you!

 

I would think a bog-standard incandescent lamp would be better suited- it will emit more radiation around 5-15 microns where the sensor is most sensitive.
IR LED's emit 0.7-0.9 micron wavelengths.

The light should flash ~ 2Hz to trigger the sensor, and the light should best hit only half of the detector area.
This will make the sensor think it sees a real moving target.

 

Here's what I determined on the U3 chip, considering pins numbered 1 through 8 with one at upper left corner and going counter-clockwise from there. Pin 1, no voltage either way. Pins 2 and 3, no voltage without motion, but 3.3 when LED is on. Pin 4, nothing. Pin 5, 3.3 volts either way. Pin 6, .6 volts either way. Pin 7, 3.3 volts either way. Pin 8, 3.3 volts no motion and 1.3 volts when motion detected. Interesting, no?

Okay thanks, what is the number on the chip U3?

 

A red LED may also work, and possibly a small incandescent light could also work, running on a lower voltage, since the motion detector triggers from body heat, not visible light. So a bit of experimenting may be required. I had not considered the different IR wavelengths, But SS is correct.
And for the current limiting resistor , given that the LED does not want to run at maximum current, I suggest getting both a 560 ohm and a 680 Ohm resistor, because the forward voltage of the LED is unknown.

If we know more about the actual application it is certain that additional advice will be available. AND some of that advice can be very useful, because here there is available a whole lot of experience from folks willing to share.

 

Okay thanks, what is the number on the chip U3?

There are faint markings on the U3 chip but illegible even under a USB microscope, unfortunately.

 

It may be that multiple flashes are required to trigger the detection, but that will require some experimentation. And the intensity of the IR falling on the PIR sensor may need to be adjusted because of the different sensitivity peak wavelengths. It might also be that a small light bulb will be the best way to produce the best wavelength. So there may be a bit of experimenting required.

 

It may be that multiple flashes are required to trigger the detection, but that will require some experimentation. And the intensity of the IR falling on the PIR sensor may need to be adjusted because of the different sensitivity peak wavelengths. It might also be that a small light bulb will be the best way to produce the best wavelength. So there may be a bit of experimenting required.

Experimenting is my middle name, I'm getting started and will let you know the results!

 

Experimenting is my middle name, I'm getting started and will let you know the results!

Success. I attached a 3-LED bulb from a small flashlight to the center of the plastic fresnel lens of the original motion detector case so that when illuminated it shone directly on the PIR sensor. Wired that up to the 9 volt battery of the sensor, and put a mercury switch into the circuit. The sensor now sends the signal to the transmitter each time the LED bulbs turn OFF, so now when the mailbox door is opened, then closed, the receiver sounds in the house exactly as I had hoped. Thanks so much to Mister Bill, Dodgy Dave and all who contributed time and thought to this project!

 

Some times a simple solution is what works the best.