Reverse Engineering a FAD Buoy - Page 1
Forum section: electronics / projects

author: waymond91
author_rank: Regular Contributor
timestamp: April 10, 2023, 04:17:57 pm
content: Hello everyone!I am working on recycling a solar panel, battery, and charging circuit from a FAD buoy. These little drift buoys have an iridium module, a gps receiver, echosounder, solar panel, battery etc. They are set adrift in the ocean report their fish finding results via iridium. This particular model has quite a few of its part numbers lasered off...For the time being, I am just trying to deciper the solar charging circuit. The buoy has 3 battery alkaline battery packs that connect to the main board, but it seems like only of them is actually rechargeable.Im hoping to use this pack to power a raspberry pi zero and cellular modem for short periods throughout the day, although Im begining to fear that this will require quite a bit more power than the solar panel and batteries can provide...The 3 battery cells are connected to J7, J5, and J8 in the picture. The solar panel plugs into the 4 pins left of the battery connectors on the flip side of the board, although the two left most pins are the only ones used.The solar panel is hooked up to a mic5239 (U24 in the photo):https://datasheet.lcsc.com/lcsc/2204261215_Microchip-Tech-MIC5239YM_C637585.pdf.The output of the regulator has a feedback resistors of 10k and 1k (R70 and R72 respectively in the photo), which according to the data sheet should set a voltage of 13.5v, this is also what I have measured.The output of this regulator passes through a diode (D12 in the photo). From here it connects to the high side of the rechargeable pack.This then goes through another diode (D11 in the photo).At this junction the other two alkaline packs connect, however they are also going through a diode (D13 and D10). So it seems as if no current can ever enter these packs.What is confusing me is R71, it is connected to the regulators feedback pin and to ground, with a nominal value of 5.6k. For the life of me I dont know what this for.What do you guys think? Is it foolish to think that I can power a pi with this? Any ideas why the 3rd feedback resistor is there?Im very dissapointed that the whole battery pack is not rechargeable, especially considering that the larger alkaline cells are the non-rechargeable ones...Photos of the entire board:https://ibb.co/478vFmJhttps://ibb.co/Kq05qR6I also made a few video explaining the project a bit if its of interest - linked below:What is a FAD buoy:https://youtu.be/gBsPCVGvEN8Buoy Teardown:https://youtu.be/eu3AFECX1LoBoard Review:https://youtu.be/WN8OUg3GqV0Thank you in advance!**EDIT**If anybody has experience with these iridium modules and whether or not they can be repurposed to a new customer, that would also be a huge help! I know that the communication protocol is supposed to be a UART, however, I assume that since they are already provisioned for an existing customer it might not be possible to re-register them...<a target='_blank' href='https://whatsmyscreenresolution.com/'>howto check monitor size

author: alexhofford
author_rank: Newbie
timestamp: May 04, 2023, 10:12:09 am
content: Hi waymond91!I have a few technical insights on these FADs that you may be interested in, having dived under them whilst I was on various photography assignments in the Pacific Ocean. Please do feel free to get in touch with me on email any time.Kind regards,AlexAlex HoffordMarine Wildlife Campaigner and Trusteealex.hofford@sharkguardian.orgMob/WhatsApp: +447366200761Shark Guardian - Shark & Marine Conservation WorldwideUK Charity #1152654www.sharkguardian.org