Trying to identify the purpose of a circuit with a PIC18LF6622

Question

I'm wondering if anyone can help me in identifying the purpose of this board?

I found it walking to my car in parking garage. It was packaged professionally in a project box with 2xAA for power (3V) and some silica gel.

The lid has a rubber gasket embedded. No openings or access through the box or lead without opening it up. No markings on the outside or inside other than what is silk screened on the board.

I think that is a 5 pin jtag type port on the left side of the board. The two silvered components are rf transceivers, large one operates 433.72mhz to 434.12mhz and the small one on the left is 916.3mhz to 916.7mhz. Pulled that data from Mouser.

Thanks!

shabaz · Answer

Hi Michael,

That gets more interesting.. I could just about read the marking on U1, but not U2. However, the marking of U1 is HMC52L which is more than likely a Honeywell HMC1052L (PDF Datasheet) device which is a magnetic sensor,. It could have been used to perhaps detect the presence of a vehicle if it altered a magnetic field. There is a 'magnetic anomaly' circuit in the datasheet and it specifically refers to it being useful for vehicle detection, see the bottom of page 8 and figure 5 on the next page in the datasheet (fig 5 is also pasted below). Looking at U2 in the photo, it is likely a dual op-amp because of the vast amount of resistors surrounding it, or some other analog signal processing. It is likely amplifying and processing the signals from the HMC1052L as in figure 5.

In some car parks, there are sensors that detect which parking locations are occupied; I'm wondering if this was to do that. I've never seen the devices so this is just a guess.

I wonder if the two radios are to communicate to two separate systems (sometimes there is no link between systems, e.g. a retail store may want to collect parking stats separately to the firm managing the car park perhaps) or the manufacturer just made the same hardware and just reprogrammed it (or set it with the DIP switches) to enable one of the two radios depending on customer preference or some site survey.

As an experiment if you have access to an oscilloscope you could try to see if there is any data on the logic level input to the radio modules when a large piece of metal is brought close to the board (it may perhaps take a minute to update, if they put the board to sleep for long periods of time to conserve power).

Furthermore it should be possible to probe where the op-amp circuit connects into the microcontroller to see that the signal looks like away and close to metal objects.

Trying to identify the purpose of a circuit with a PIC18LF6622

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