I am want to create a switch that will power my microcontroller as well as the 2 ESCs that control two brushless motors. The ESCs run at 30A thought the motors only require 13A. I am thinking to create the following circuit: Use a switch to turn on the microcontroller (Arduino). Then use the Arduino, through one of its output pins, to turn on a relay that will connect the power supply to the ESCs. My idea is shown in the attached picture. Switch Circuit Can someone help me with the correct relay to use as well as other parts (transistors, diodes, resistors, etc) that might be needed? I will also like to see a complete schematic of the circuit if possible. Thanks

  • \$\begingroup\$ Why are you bothering to add the relay when you could just have the switch enable the ESC instead? If you put the switch between battery (+) and the ESC then you can have the microcontroller powered by the battery eliminator circuit (BEC) on the ESC. Thus one switch turns everything on and you don't need the weight of a relay. \$\endgroup\$
    – Chuck
    Commented Jul 12, 2016 at 12:22
  • \$\begingroup\$ What is the point of Q1? \$\endgroup\$
    – JSycamore
    Commented Jul 12, 2016 at 13:58

1 Answer 1


Instead of using a transistor and a relay, you can use a single Power BJT to control the ESC from the Arduino.

BU931P BJT will suite your purpose.

DataSheet: http://www.st.com/content/ccc/resource/technical/document/datasheet/2d/82/a7/66/ea/d0/47/c4/CD00000005.pdf/files/CD00000005.pdf/jcr:content/translations/en.CD00000005.pdf

enter image description here

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    \$\begingroup\$ that would destroy the transistor \$\endgroup\$ Commented Jul 14, 2016 at 10:37
  • \$\begingroup\$ oops..may i know why? @Jasen \$\endgroup\$
    – Arvind
    Commented Jul 14, 2016 at 11:35
  • \$\begingroup\$ your arduino puts out 5V on the base, so the voltage on the emitter is about 4.4V and the voltage on the collector is 12V, so a 7.6V drop. if the motor needs 30A that's almost 230W heat created in the transistor. plus the motor is only getting 4.4V so it will be slow, \$\endgroup\$ Commented Jul 15, 2016 at 11:56

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