Automotive Transient / Input Filtering Schematic - Page 1
Forum section: electronics / projects

author: WaldPinkler
author_rank: Contributor
timestamp: March 18, 2022, 12:50:07 am
content: I'm still struggling to pick a solution to transient input filtering for some projects I want to add to a yacht (alternator, large winch, large electric bow thruster motor, fridge compressor, bilge pumps, etc).Protecting LED drivers, USB power supplies, PI boards, etc.Here are a few automotive schematics I've come across for input reference designs. How do I choose?3 attachments:ST LED driverTI LED driverOnsemi 100w USB

author: DeanA
author_rank: Regular Contributor
timestamp: March 18, 2022, 02:56:19 am
content: Here's another one to consider. This is low side protection for reverse polarity and load dump overvoltage. Pros are low voltage drop and power dissipation.How do you choose? Depends, have to weigh up the pros and cons of each I guess.

author: viperidae
author_rank: Frequent Contributor
timestamp: March 19, 2022, 06:00:28 am
content: How does that work DeanA? Is that zener between the resistor and base of the transistor around the wrong way?

author: inse
author_rank: Super Contributor
timestamp: March 19, 2022, 07:15:47 am
content: First of all, I would make up my mind about what kind of disturbances you might encounter on an yacht, automotive standards may be overdone.Reverse polarity?Load dump?Jump start (24V)?I would think of: fuse, transil, 100nF+ MLCC, electrolytic according current consumption.Inductors are more difficult to select.P.S. netter Aliasname

author: WaldPinkler
author_rank: Contributor
timestamp: March 19, 2022, 10:23:08 pm
content: For sure a load dump when lithium BMS disconnects while engine alternator is running.Large inductive load voltage spikes. Thruster motor has a 400A fuse for some scale. Winch at 80A.Negative spikes from relays.Of course a jump start may be required.My stupidity from accidental polarity reversal on batteries.Plus all the noise from a fridge switching on and off, autopilot hydraulic switching back and forth, bilge pumps, a wind generator which is probably noisy as hell.I agree automotive standards are probably overdone but I wouldn't know where I could scale back from there.

author: inse
author_rank: Super Contributor
timestamp: March 20, 2022, 06:59:30 am
content: I wonder how the lithium battery is integrated into the net.I know in cars nowadays there is a complex energy management with tracking the charge state of the good old lead batteries and control of the alternator according demands.If you have similar on your yacht, load dump shouldn't occur.Can you tell more about the battery used?Jump start is the automotive requirement of the car being jump started with a 24V truck battery and everything has to survive (I always wondered about the light bulbs).Why do you have a wind generator on a yacht, when is this used?Is it a motor yacht or sailing yacht with motor?

author: WaldPinkler
author_rank: Contributor
timestamp: March 20, 2022, 08:42:40 am
content: Sailing yacht with large diesel motor.The lithium batteries just drop in and replace the lead house bank. There's still lead for the engine or they can be paralleled with a switch for emergency engine starting/backup.The BMS in the battery just has standard over voltage, under voltage, over current, temperature sensing. It just disconnects the battery. There's no smart sensing involved other than shunt measurements on the panel.The wind generator runs when it's windy. It's also basic. There's just a way to set the maximum voltage when it turns off or I can manually switch it off. The current out of it is extremely erratic, the wind isn't a smooth flow at the back of the boat plus the land.So the lithium can easily create load dumps disconnecting and large electric motors can generate good spikes.

author: DeanA
author_rank: Regular Contributor
timestamp: July 04, 2022, 05:17:43 am
content: Quote from: viperidae on March 19, 2022, 06:00:28 amSorry, missed your question months ago. Yes sorry, that zener is around the wrong way as you rightly picked up.

author: jonpaul
author_rank: Super Contributor
timestamp: July 04, 2022, 05:56:10 am
content: Use large area TAZ specifically designed for vehichle 12/24/28V bus protection.We used MR2525 and MR2535 in 1980s avionics designs.https://www.digchip.com/datasheets/parts/datasheet/131/MR2525-pdf.phpGreat part, huge junction, but Old and obsolete, modern equiv exist for sure.Jon