Hi guys,
I'm thinking over new multicopter power distribution board which will integrate also 4 current sensing shunts, two dual current/voltage/power sensors, a 42 Vin 3A DC-DC Buck regulator. The current,voltage and power measurements will be carried out over I2C interface. I think it's time to place aside the analogue measurements as there are a lot of clever ICs for the purpose.
Some explanations:
1. R1-R4 are 4 current shunts. Each of them can handle 60A...or even more, but some more thermal researches should be done;
2. US1 and US2 are dual current/voltage/power sensors with I2C interface;
3. U6 and surrounding passive components are the DC-DC Buck regulator;
4. The PCB is 6 Oz double sided with glued heat sink ( optional...if needed ) on the bottom layer.
As this is just a preliminary idea, I'd like to know your pro and cons about the design.
Best regards
Nick
Comments
I like the idea of I2C based power supply and voltage/current readings to the flight controller. Makes cabling simpler and potentially allows further reduction in size (less connectors etc). It would also allow better scaling to measure multiple batteries and I've even thought of applications for reading individual cells to better understand battery performance and protect against failures.
I've seen a power supply board that required you to drop a solder line over the wide trace prior to use.
What is the focus of your design? 240A is an enormous amount of current and it sounds like you're targeting really heavy lift copters. Normal quads would draw around 25-30A continuous with peaks towards 50A.
Yes. Btw, it can be possible to join both BAT+ pads, but I'm afraid the + and GND must share the bottom layer which will lead to not wide enough + track....at these high currents the cable section will be times higher than the + track section......a bit difficult. Another reason to separate BAT+ current is the opportunity to use two batteries. If one battery supplies the odd motors, while the other supplies the even ones, the redundancy could be a bit higher.....one can probably still land the copter safely.....maybe.... :-)
Sorry, I missed that part. In that case it would be only a software change for ardupilot / pixhawk systems.
It is I2C as stated at the beginning of the thread.
I do not see how shorting the two batt+ contacts on the board would be any different from using a Y harness to connect both sides to the same battery. Also how are you getting the measurements out from the board, looking at the 4pos header you have I assume that you have 5v+, gnd, and two signal lines, but that would only allow two measurements, are you sending serial data out? What format is the communications?
Yes, the first idea was to use Al substrate 2 Oz single layer board thus heat sinking the tracks. If I move the DC Buck to a piggyback board it could be done. But if I short the two BAT+, I won't be able to measure all 4 shunts anymore. Btw, the bottom side is almost a GND plane and all GNDs are connected to.
I think you could easily connect the pos and neg connections together on the bottom side of the board. It looks like you have designed this to be a single sided board, If you did not mind doing a double sided load you could have the other BEC on the bottom side, but this will drive the cost up and could make it harder to mount. I also doubt you will need that heat sink, if the board is in an area that does not get enough air flow already to cool it then chances are the heat sink will not fit or be able to dissipate the heat anyway.
Hi Justin,
The two battery terminals are not connected on the board, but just with OR-ing Schottky to the DC-DC Buck. If you use a single battery, you have to make two Y cables - one for (+) and one for (-).
About sensing the two battery terminals...I have to think on your idea.....thus just one dual current sensor would be enough.
About the additional voltages.....it is possible, but the board may need to get larger. Do you know how large it could be...mean the maximum allowable dimensions?
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