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I'm making a quadcopter with two little grabber arms. Here's the relevant hardware I currently have:

  • 1500mAh 100c 14.8V (4s) lipo battery
  • 2s-6s flight controller that's rated for 45A burst current (times 4 motors) = 180A max
  • 5V OpenRB-150 servo controller that powers 6 small servos drawing maximum 10A (together)
  • 11.1V power supply to 6 servos drawing maximum 10A (together)

From what I've gathered on forums is that I should connect a busbar to the battery and connect some DC/DC converter to the busbar to the different controllers/servos according to their voltage.

Wouldn't the busbar divide the voltage between the converters and/or cause noise or something? I'm an electricity novice and this is the first time I'm making a robot at this detailed level.

I've also read about PDB's, but they seem like overkill because I'd have to get a giant PDB that would provide 180A to the FC from one of the terminals when the the other controller and servos only need 10A each.

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  • \$\begingroup\$ 1500 mAh? That's tiny for the load you're giving it. \$\endgroup\$
    – Hearth
    Commented Apr 22, 2023 at 4:37
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    \$\begingroup\$ And please, please don't try to get useful answers out of GPT. It is not a knowledge base, it is not giving you true statements, it's giving you things that look like an answer to what you ask because that's what it's designed to do. It is not, and is not intended to be, capable of answering questions correctly. I don't know why people are hyping it up as though it's some amazing solution to everything, but it's not. \$\endgroup\$
    – Hearth
    Commented Apr 22, 2023 at 4:40
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    \$\begingroup\$ At full power to all lift motors (180A,) your battery will last for less than half a minute. At 100c, 180A is more than your battery is rated for (150A.) \$\endgroup\$
    – JRE
    Commented Apr 22, 2023 at 10:50
  • \$\begingroup\$ What current do your lift motors really draw? \$\endgroup\$
    – JRE
    Commented Apr 22, 2023 at 10:51
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    \$\begingroup\$ Four motors at 35A each is 140A. Your 1.5Ah battery will last for less than one minute. You'd need something like 9Ah for four minutes. \$\endgroup\$
    – JRE
    Commented Apr 22, 2023 at 16:45

2 Answers 2

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Find a SMPS (Switch Mode Power Supply) (aka Buck converter) that will deliver 5 V at 10 A. Connect the input to your battery, the output to your 5 V servo controller.

Find a SMPS (or a linear regulator) that will deliver 11.1 V at 10 A. Connect the input to your battery, the output to your 11.1 V servo controller. The reason I allow also a linear regulator here is that the efficiency of some SMPS's is so poor, that with this small voltage step down, a linear might almost be as efficient. A SMPS should be more efficient, and will be smaller and lighter, than a linear, so is still preferrable.

Although your 100C battery is capable of delivering 150 A, that doesn't mean you should use it at that current. Using it at very high current reduces the capacity and lifetime significantly. If you have the payload available for a larger battery, it may be worth thinking about.

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  • \$\begingroup\$ SMPS is the same thing as a buck converter right? I'm having a hard time finding DC input SMPS's (they seem to come in AC input current) but I'm finding lots of buck converters that seem to be doing the same thing. Also, I decided to go with a 90C 9500mAh battery - thanks \$\endgroup\$
    – Brian
    Commented Apr 22, 2023 at 19:35
  • \$\begingroup\$ @Brian Yes, I should have called it a buck \$\endgroup\$
    – Neil_UK
    Commented Apr 23, 2023 at 5:39
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I should connect a busbar to the battery and connect some DC/DC converter to the busbar to the different controllers/servos according to their voltage. However, wouldn't the busbar divide the voltage between the converters and/or cause noise or something

A busbar is a thick copper bar used to distribute the supply voltage to several devices that require high currents and/or high current pulses while maintaining (not dividing) the voltage value. It is thick to reduce resistance and inductance.

The use of a busbar is appropriate in this case.

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  • \$\begingroup\$ Makes sense - thank you. So I could probably connect the FC directly to the bushbar without any sort of converter, right? \$\endgroup\$
    – Brian
    Commented Apr 22, 2023 at 19:40
  • \$\begingroup\$ The voltage must be correct for the FC. youor battery seems alittle light though. \$\endgroup\$
    – RussellH
    Commented Apr 22, 2023 at 19:53

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