Haking the newer Harbor Freight Driveway Sensor

Just bumping for someone to take interest. :-) Mikek

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I would guess the AT12L is an indication it is an Atmel custom chip, likely an MCU with custom programming.

I can't say I understand what your device is. Is this a remote control dev ice with a remote button to activate something, the piezo and LEDs only? I think you will have to wire up your own piezo to the button. Mallory make s some nice alerts that are designed to be panel mounted.

Rick C.

All these modern systems transmit a code to identify the particular sensor type/location to the master control. It's probably simplest to get another dummy sensor and activate that to initiate the test.

Oh, sorry, it is the Bunker Hill Driveway Sensor sold at Harbor freight. You have a transmitter that will sense when someone or something enters it's area. Pretty sure it uses a PIR sensor. The transmitter then sends a signal up to 400ft (?) to the receiver.

I think the 319H is the relevant number, but not sure. >> Might be a pic. I think this, >

ceiver.

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kely an MCU with custom programming.

device with a remote button to activate something, the piezo and LEDs only ? I think you will have to wire up your own piezo to the button. Mallory makes some nice alerts that are designed to be panel mounted.

Ok, so you are talking about the receiver which doesn't really care much wh at is doing the transmitting I expect. So the RF link is most likely the s eries of pulses you are seeing on the output of the RF receiver. Since thi s is battery operated, I don't expect a signal is being transmitted continu ously as the transmitter uses a single 9 volt battery. This would say to m e the signal you are seeing on pin 4 is not the received RF.

I don't have any suggestions on how to false trigger the thing from a push button without adding an MCU between the receiver chip and the MCU on the b oard. This MCU can generate whatever signal is required. But that would b e some work and I expect you are looking for a quick fix.

What is the part number of the RF chip?

Rick C.

Why not just buy a wireless doorbell?

no. but do you know how pyroelectric sensors are read? feed that input with a few Hz at low amplitude.

I had one of these driveway sensors modified and it worked fine for years. My business is 3 steps down, I put the sensor on the middle step, then when someone walked down the steps, the receiver was triggered and the obnoxious noise from the piezo would wake me up. Then maintenance changed the steps, the jerk must have been very curious what was inside this pvc pipe. So he cut the wire and took it. When I ask him about it he didn't know anything about it. He is what we call a liar. So, now I'm modifying another one. I have to modify it because it will trigger on every car that goes by, every pedestrian and every customer that stands in front of my while we do business. Just want it to trigger in that two or three foot area as they descend the stairs. Doorbell, yes, I just wanted the doorbell button to cause the same piezo to sound, that's in the driveway receiver.

No, I didn't but I did look at this site and got some idea.

I'm still lost, as the rf section has that constant pulsing output that changes when the receiver gets triggered.

I took the perfectly working assy, wallwart, voltage regulators, receiver and sensor, which I had working just fine at home, down to the business. I wired it all up and installed the sensor where it needs to be and the receiver, just will not stop beeping.

I'm going to try another section of the fresnel patterned window and mount it differently. I have the PIR looking through a 1/2" piece of tubing with the window on the end. (same as the old unit)

I tried twice to clean this off my screen --> ? Eyes aren't what they used to be. Mikek

Why can't you just leave the fresnel where it is and modify the shape of the pipe to get the coverage you want? Have it view only the bottom step.

Maybe worth a try!

SFAIK they use OOK in the transmitter. The receiver adjusts the gain until it sees 50% signal

It'll be receiving everything else that shares the same band (car remotes, door remotes, doorbells, noise, etc. So you'll get binary noise until a nearby transmitter comes on and the AGC pushes the noise floor down below the threshold.

I hate it when that happens :(

I've seen similar units with black electrical tape covering most of the fresnel zones, resulting in a narrower view angle..

:) I was looking through unicode for some reason and came across that character, and thought "He looks happy"

This morning I may have noticed why that happened!

My business is on the water, 3 steps down to the dock. The dock is against a concrete wall that goes below the water line. I point my sensor at the concrete wall, not a problem, but, when they replaced the steps they also replaced dock boards. The original dock boards were 6'6" long, the replacements are 6 0" long, leaving a 6" gap along the wall. I noticed this morning the sun reflecting off the ripple of the water and hitting the wall. My theory is the rippling reflection though the gap was causing the continuous beeping. On my next test, I'll put a board over that gap. The marina owner saved money by cutting a 12' board in half, it cost me when a dropped phone went into the water through that gap. "It's always something" Mikek

I had a similar problem with sunlight through tree-leaves.

You guys know how the "motion" sensor works, right? They use a "lens" that causes a moving IR source to vary the intensity of the light falling on th e photoreceptor. I haven't taken one apart, but I expect they use at least two photoreceptors so changes in overall brightness doesn't trigger the de vice. So light patches varying in intensity will trigger the device if the y contain IR energy.

A friend was talking about a sensor that was getting triggered at night out side her mother's home which upset the mother thinking someone was trying t o get in. The daughter though the IR sensor was picking up tree branches m oving since it is a "motion" detector. I tried to explain that the branche s were the same temperature and so wouldn't trigger the detector. But then I realized, if a strong light were behind the branches it might have enoug h IR to trigger when the branches moved. She didn't see the need to involv e a light source.

Rick C.

As I understand it:

The sensor produces current as its temperature changes. The pyroelectric element has two cells and the lenses in adjacent zones of the window focus incoming infrared on opposite cells. the two signals are fed to opposite inouts of a op-amp and the amplitude of the output signal is checked

On Aug 11, 2018, Jasen Betts wrote (in article ):

It?s called a pyroelectric IR sensor:

Joe Gwinn