I am developing robot for a project. For that i have to control 5 servo motors of different types. Here are my servos..

Power Pro MG995 (4.8 V to 7.2 V)

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Savox SW-0250MG (4.8 V to 6V)

enter image description here

And my battery is

DUPU 1500mah lipo battery

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Before try to use my battery, i powered Savox servos with an Arduino board (5 V ouput). Servos work fine. Then i replace savox servos with MG995 servos. But they don't work as expected. That mean they are not rotate as I coded. Servo stops some times. Kind of a power problem. I think it is due to low voltage (5 V since it can operate up to 7.2 V).

Then I buy my lipo battery and I still unable to reduce 8.4 V into 6 V.

Can someone suggest me a method. It I able to do that, will I able to run MG995 servos as expected??

Any help would be greatful Thank you in advance!!!

  • \$\begingroup\$ A 2.4 V zener diode in series? An LDO? A buck converter? \$\endgroup\$ – winny Jul 17 '18 at 20:06
  • \$\begingroup\$ As this comes from RPi SE, I think you missed the Raspberry Pi GPIOs are +3.3V, not +5V. \$\endgroup\$ – Janka Jul 17 '18 at 20:06
  • \$\begingroup\$ @Janka Thank you. can you explain it a bit. I am only give signal from raspberry pi to servos. I have problem with the external power supply. I suppose \$\endgroup\$ – iuhettiarachchi Jul 17 '18 at 20:14
  • \$\begingroup\$ In your question, you say you are using an Arduino with 5V out. Now you say Raspberry Pi? Is the servo connected directly to I/O or is there something providing higher current and/or an external voltage source? Raspberry Pi I/O does not have enough voltage. And an Arduino, I would wonder if it could source enough current. Can you make your question more clear? \$\endgroup\$ – evildemonic Jul 17 '18 at 20:17
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    \$\begingroup\$ A link to the datasheets for your components would be much more helpful than a photo. \$\endgroup\$ – Elliot Alderson Jul 17 '18 at 20:34

Use this simple circuit to lift the voltage level to that of the servo:


simulate this circuit – Schematic created using CircuitLab

What does it do? Q2 switches the output to the servo between 0V and +8.4V (or whatever you apply there). It's normally conducting, because of the current into its base through R2, so the servo output is 0V. If the RPi GPIO is switched ON, Q1 conducts, so Q2 falls short of base current and stops conducting. Then, the servo output is pulled to +8.4V through R3.

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  • \$\begingroup\$ This might burn out his servos. The Tower Pro MG995 is known for burning out even at 6V. \$\endgroup\$ – evildemonic Jul 17 '18 at 22:21
  • \$\begingroup\$ Well, then +5V instead of +8.4V. As the Raspberry is +5V powered, that should do the trick. \$\endgroup\$ – Janka Jul 17 '18 at 23:22

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