Arduino using a servo with an external power source, suddenly voltage drop

[danielz1983]

Hello

I am pretty new to arduino programming and also electronics in general.

I am using an arduino which is powered via usb.
The arduino controls a servo which is powered via an 18650 battery shield with one 18650 battery (soldered to the 5V output).
As i do not want to have my battery running out of power that fast, i have a relay between the servo the arduino and the external power source.

Actually it works quite fine and the arduino controls the servo.

But after some turns of the servo, the 5V output pins of my 18650 battery shield suddenly drops to an output of 1V and then of course the servo stops working. I have tested this with a multimeter.
When i remove the battery and insert the same again the 5V output produces again 5V.

Do you have an idea or do you need more infos about my setup?

My setup:

Battery: SAMSUNG LI-ION-AKKU NR18650-25R
Battery shield: ARCELI Wemos 18650 Battery Shield V3
Servo: Miuzei 270° Digital RC Servo Motor 20KG
Relay: ARCELI KY-019 5 V
Arduino Uno Board

[UKHeliBob]

Welcome to the forum

Please post a schematic of your circuit

[Railroader]

@danielz1983

(soldered to the 5V output).

What 5 volt output?

@danielz1983

i have a relay

That can be bad. Arduinos don't have power enough for a relay.
Please post links to the datasheet for the relay.

And as already told, post real schematics, not Fritzing toy pictures.

[jremington]

That high torque servo is overloading the 5V boost converter. Try to find the "stall current" rating for it. It is probably 3 Amperes or more.

Servos and other brushed DC motors draw the stall current every time they start moving, and the servo power supply must be able to easily deliver more than that.

[danielz1983]

The stallcurrent of the servo is: * Stallcurrent: 2100mA±10% (4,8 V) -2700mA±10% (6,8V)

The relay is a 5v relay module.

I think i know maybe the issue, the battery shield with 1 18650 battery can deliver max 1A output current. But the servos stall current could use up to 2.1A. So i need to use a battery shield with 2 batteries to have a higher output current. Do you think so as well?

[camsysca]

That drawing is wrong. +5 to relay coil, relay coil to Arduino 5V? How could that work?

[TomGeorge]

Hi, @danielz1983
Welcome to the forum.

Can you please post some images of your project so we can see your components and layout?

Can you please label the terminals on your relay?

Please hand draw your circuit so you can draw the relay as it really is.
Sorry its a Fritzy, but this is how you connect up one of those relay modules.

Tom..

[danielz1983]

Sorry that i drew it wrong, i was not sure how to read this relay stub on this online circuit drawer

But my assumption was correct, a 2 18650 battery holder was needed, now there is no voltage drop.
But i will add a picture of the working project here