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gauteh / sfy

🌊 A lightweight wave buoy for near-shore deployments.
MIT License
42 stars 6 forks source link

Voltage regulator: Need to support 2A burst #20

Closed gauteh closed 2 years ago

gauteh commented 2 years ago

https://www.pololu.com/product/2122 does not work, cellular modem needs 2A bursts. Sparkfun (https://www.sparkfun.com/products/18356) buck regulator works, but requires 3.8V input (3 D-cells gives 4.5V), which reduces how much of the battery can be used.

Maybe use https://www.pololu.com/category/146/s18v20x-step-up-step-down-voltage-regulators if we can work with 5V.

gauteh commented 2 years ago

The notecarrier can take 2 - 5V on Vin, so if the voltage regulator is not used to power the notecarrier we should be ok with the pololu. https://discuss.blues.io/t/qwiic-notecarrier-with-sparkfun-redboard-artemis-power/472/3

jerabaul29 commented 2 years ago

May need to check that the voltage does not go under 2V still - even if 2V sounds really low, would need a lot of draw to get that low... Another possibility may be to put some supercap(s) at the right location maybe? This is what is done with the AGT to help the iridium modem get enough power when it is having a pulse of current use.

gauteh commented 2 years ago

At 2V the Pololu is also out. Are you thinking that the burst of 2A makes the voltage drop below 2.7 directly on the batteries?

jerabaul29 commented 2 years ago

I am indeed a bit worried that when there are large power bursts, slightly depleted batteries, and low temperatures, all involved at once, power issues may arise, including battery voltage dropping really low... Looks indeed like a LSH20 should be fine to use according to https://www.batterionline.no/media/blfa_file/LSH20.pdf , but not sure of alkaline batteries for example - not sure of how their voltage curve looks like, and how it looks like at different discharge levels. I like that SF had added some supercaps to mitigate the problem to some degree with the iridium modem, wondering if adding a supercap at a well chosen location may help (simplest is even in parallel to the batteries...).