PCB Traces - And Hi! - Page 1
Forum section: electronics / projects

author: Toffe
author_rank: Newbie
timestamp: September 10, 2015, 07:20:08 pm
content: New to this forum.I'm currently designing a PCB for my ROV project. (underwater vehicle).My goal is to have a "control board" which controls the thrusters which are i2c enabled via speed controllers. I also want some sensors connected to that same PCB.The idea i have in my head is a board which has a "main power in" adapter with a XT90 (90amp) connector soldered to it. From that 90amp connector it goes to smaller connectors (screw terminals?) with 12amp each max. I also want a current sensor on each output and possible one on the "main" trace.The problem is that i dont know how to achive the current sensing (INA219B i heard had i2c, with a shunt or something it might work?) and mainly how to do the high current pcb traces to not get hot! Since this is in a comfined space up to 100 meters depth i hope it can be "cool" as possible.I dont know if anyone understands me, but i would be glad if you think you can help and ask more to get the info you need.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 10, 2015, 08:22:02 pm
content: There is this tool...http://www.saturnpcb.com/pcb_toolkit.htmBut, do you really want to use a pcb to interconnect a 90 Amps supply? Not that it is impossible, but you might want to use a thicker copper layer for that.Yes, you'll be needing shunts with that INA. You can't magically put the chip on top. Example shunt: PMR100HZPFU5L00It is 0.005 Ohm. That'll be 0.72 Watts with 60 mV signal. The key point here is mV/A and heat loss. Using a 1 Ohm shunt will give 12V signal, but also 12W.There are hall sensing current IC's you just put on top of the trace, very useful if you want to know if there actually is any current. But they are often inaccurate. But you'll be able to detect no, a bit and a lot of current.There are also the famous Allegro Microsystems current sensing hybrids that take any current and spit out isolated 0-vcc analog. Depending on the cost, these might be the ones you'll be looking for: ACS756 and such.I assume the motors are pwm controlled, that'll have a lot AC components. You might need to filter/shield from that.

author: Toffe
author_rank: Newbie
timestamp: September 13, 2015, 03:10:03 pm
content: Hi.I would love to have everything in a PCB instead of using lots of cables. its not 90 amps but just a 90amp connector.The max current pr. motor is 11.5A which will result in 69 (6x) if everyone went full speed at once. I'd say its up to 50AMP max at once. The ESC's are controlled via a i2c interface not PWM. Just because i want to reduce the number of cables i have to connect to my "main" pcb. This will be only motor / some sensors on. The main PCB is possible a beaglebone blackI dont have any hands on experience so thats why i ask about this. Any other idea on how to do it?My idea is:Battery -> Current sensor (Total current) -> to every esc with a current sensor pr. esc -> motor

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 13, 2015, 04:45:50 pm
content: 1) dont solder mask the power traces, tin with thick solder or put heavy copper in the line and solder them...2) whats the purpose of each current sensor to ESC? if its ADCed to the mCU you can sum them all, then no need total current sensor at battery, thats a waste.3) couple the pcb to the ROV's body, you have abundant of heatsink down there...