EPIRB - Page 1
Forum section: electronics / general

author: mojoe
author_rank: Frequent Contributor
timestamp: January 28, 2023, 08:54:24 pm
content: I had the opportunity to take some pictures of an EPIRB that was on its way to disposal.For those who don't know, EPIRB is "Emergency Position Indicating Radio Beacon", and they are used aboard ships. When activated, it sends out a radio signal to some SAR (Search and Rescue) satellites, on 406 MHz. Each EPIRB is registered to a particular ship, so the radio signal contains the ship's ID number. With a standard EPIRB, the satellites triangulate a rough position of the transmitting EPIRB. This information is then sent to a ground station, where the appropriate SAR authorities are notified. This is similar to how an aircraft ELT (Emergency Location Transponder) works.A second type of EPIRB has a GPS receiver, so it can send a more exact position to the satellites. It also stores data from the ship's VDR (Vessel Data Recorder), for later retrieval. In Pics #5 and #6, you can see where a memory chip and a GPS antenna would go. One PCB for either model.Pic #1: The cover is unremarkable, with just some basic warnings and labels.Pic #2: Inside the housing is the EPIRB, in its mounting bracket. You can see the slide switch, used for testing (push to the right and hold until the LED blinks), and for activation (push to the left, breaking the safety wire). The spool of line that hangs on the side was cut when the EPIRB was opened, to disconnect the battery. Behind the top of the EPIRB, you can see the hydrostatic release mechanism. When the ship is under water, the hydrostatic release pops the cover, the EPIRB automatically activates, and floats to the surface.Pic #3: A closeup of the hydrostatic release and the spring housing.Pic #4: The bottom of the EPIRB contains a large non-rechargeable lithium battery pack. These are good for five years, and are regularly inspected for expiration date (marked on the outside). The cells looked about the size of 18650's. I could not disassemble further, as the EPIRB was being sent for dispossal. Some dessicant packs are zip tied to the top.Pic #5: The top half of the EPIRB, showing the circuit board. Again, I wasn't able to remove the cans. One of the cans is the 406 MHz transmitter. The other can looks like it is for an optional GPS receiver. There is no GPS antenna fitted, so I don't know what is under that can. You can see the spot for the optional flash memory chip.Pic #6: The antenna PCB plugs into the main board via a 3-prong header. It is secured with a plastic wedge, slotted into the base of the antenna PCB. The circuit at the top is for the LED strobe. There is one antenna trace on the front for the 406 MHz transmitter. You can see where a GPS patch antenna would go.Pic #7: The back of the antenna PCB has a second antenna trace, making a dipole.Pic #8: A closeup of the Atmel MCU. Sorry for the blurry picture. The ship was rolling at the time. I took several, but this is the best one.If this EPIRB wasn't on its way for official disposal, I would have done a more complete tear down.NOTE: i tried to attach the pictures, but even though they are all small, I keep getting an error, saying that each one is over 5000 KB, which is far from true. I have attached Dropbox links below.https://www.dropbox.com/s/l4wcau6ptlezr1m/1%20-%20Cover.jpg?dl=1https://www.dropbox.com/s/12vteea0k5tv0ny/2%20-%20Open.jpg?dl=1https://www.dropbox.com/s/bd6by2c2xlv19bt/3%20-%20HSR.jpg?dl=1https://www.dropbox.com/s/im39jj3qovvmwaf/4%20-%20Battery.jpg?dl=1https://www.dropbox.com/s/w7pan1to0ziujct/5%20-%20PCB.jpg?dl=1https://www.dropbox.com/s/wuwb51n6jauxx1i/6%20-%20Antenna%20Front.jpg?dl=1https://www.dropbox.com/s/m0twzqb5xxnt42a/7%20-%20Antenna%20Back.jpg?dl=1https://www.dropbox.com/s/465en86pd0870nq/8%20-%20MCU.jpg?dl=1