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I'm trying to connect an arduino with 3 sg92r servo motors on it and an RPI with and lcd and the serial of the arduino connected to it.

They are both connected to a power supply with 9v/1A and 5v/2.5A for arduino and rpi respectively.

Is this possible?

or can I just connect the arduino to the rpi without connecting the arduino to the power supply?

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  • \$\begingroup\$ Connecting the Arduino's 5V serial lines to the Pi's 3.3V I/O pins does not sound like a good idea... \$\endgroup\$ – JimmyB Feb 17 at 18:18
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Yes, what you are trying to do is possible, just connect the GND of both to each other.

Also, instead of using two power supplies you can use just one 5V power supply and connect VCC and GND from both to each other and you will be fine. (Amps will depend on your specific power consumption)

The on-board voltage regulator on arduino might not be sufficient to power 3 servos, you are better off using a 5V power supply and connecting servos to VIN instead of VCC.

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  • \$\begingroup\$ that's what I did. But I encountered a problem that my lcd burnt up. I have just one power supply with the rpi and arduino connected on it. maybe I have done wrong on the Amps? \$\endgroup\$ – Kevin Feb 17 at 5:01
  • \$\begingroup\$ @Kevin, Can you provide some details on how the power was connected to the LCD, the type of LCD ? \$\endgroup\$ – Electric_90 Feb 17 at 5:08
  • \$\begingroup\$ 7" capacitive touchscreen for pi. I just connected the HDMI and micro USB to the pi directly. \$\endgroup\$ – Kevin Feb 17 at 5:13
  • \$\begingroup\$ Is that screen the one with external LCD driver ? Please provide a link to it. \$\endgroup\$ – Electric_90 Feb 17 at 5:16
  • \$\begingroup\$ embedded-lab.com/blog/wp-content/uploads/2016/12/… it's this one. \$\endgroup\$ – Kevin Feb 17 at 5:19
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...connected to a power supply with 9v/1A and 5v/2.5mA for Arduino and R'pi respectively.

There is something seriously wrong with your current numbers. The Raspberry Pi is certainly not going to work with a power draw of 2.5mA. You also lack any real information allowing responders to help you.

Assuming:

  1. The servos you talk about are RC servos, they are likely to need 5-7V and depending on size (which you don't give) may need 100-500mA each under load.

  2. The Arduino (assuming a Uno configuration) will need 5V @ about 80mA (though you can power it via the onboard regulator with 7-12V).

  3. The Raspberry Pi (assuming Model 3) could be between 500mA and 1A depending on peripherals. It has a quirk also that you need to have slightly above 5V (the onboard low voltage indicator is set to 4.95V). It is advisable to set your power supply to 5.1-5.15V to ensure that any ripple does not impact operation. Lots of folks miss this and end up with unreliable operation.

You can power the R'Pi and the Arduino from the same 5.1V power supply, but I'd ensure that it can supply 1A to be safe.
I'd recommend a separate power regulator for the RC servos, since the stall current can be quite high.

If you have a 9V 1A supply and a 5V (I hope it's actually 2.5A) supply, I'd suggest you use the 9V supply (with an external regulator) to power your servos, and the 5V supply to power the R'Pi and the Arduino.

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  • \$\begingroup\$ oops. Edited my question to 2.5A and added info for the servo motor as a sg92r servo. sorry \$\endgroup\$ – Kevin Feb 17 at 5:12
  • \$\begingroup\$ The SG92R is a real cheap servo …..light/medium load you should expect 20-40mA. Stall current is up around 100-150mA. Datasheets for this servo are terrible, but you can see voltage ratings of 4.8-6V. I'd still suggest they should be on their own regulator. \$\endgroup\$ – Jack Creasey Feb 17 at 5:46

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