Powering servo from Battery not through Arduino

[marvinwright]

Hello

I remember reading that it sometimes (always?) is better not to power a servo through the 5V port?
I tried to find anything on this topic just now, but couldn't find any direct answer, so here's my question:

I am using

• Arduino Nano
• 2x 18650 Cable Li-ion 3.7 V 3000 mAh
• 1 x 2s BMS
• 1 x HS-755HB (Operating Voltage Range (Volts DC) 4.8V ~ 6.0V)
• 1 x TP4056 charging board

I connect the Batteries in series using the BMS and now wonder what is the best way to power the servo.

Can I connect the servo directly to the TP4056 together with the Arduino and would this be better than to connect it to the Nano 5V and GND?

Attached a schematic I made with fritzing.

Thank you in advance

[Idahowalker]

Something to note: the TP4056 is rated at 1 amp max output. A simple plastic geared servo has a stall current of around 800mA.

[marvinwright]

Good point thanks!

The stall current draw is 1800 mA.

I could also connect it to the batteries before the TP4056? I also need to fit a switch somewhere to switch everything on/off.

[Paul_B]

It is important to note that the "5V" pin on the Nano is not an output for power and that the "Vin" pin is not useful for supplying power.

For any purpose other than testing programs on the bare Nano and flashing a few LEDs with up to 20 mA, the "Vin" pin is of no use whatsoever. That quite limited "test" situation is its only function.

You need to provide 5 V - reasonably regulated depending on the application - to the "5V" pin to operate the Nano and the same 5 V will power other connected devices. You need to design your battery power system around providing a 5 V supply with your given current requirement.

[marvinwright]

Thank you.

Then I will power the arduino through the 5V. I read in other threads that the supply voltage of 7.2V shouldnt be a problem.

Do you have any thoughts on how to power the servo?

[bluejets]

Anything over 6v is going to kill the servo.

Perhaps a buck converter off the 2 x 18650's set to 5v.

[slipstick]

Personally I would use a 5v 2A or 3A DC-DC converter from the 2 series batteries and drive both the servo and the Arduino (through the 5V pin) from that.

Steve

[Grumpy_Mike]

Then I will power the arduino through the 5V. I read in other threads that the supply voltage of 7.2V shouldnt be a problem.

I think you misunderstood what you read.
It is 7.2 for powering through the internal regulator. If you connect to the 5V pin you must not exceed 5V otherwise you fry the Arduino.

[TomGeorge]

Hi,
I think you had better check your "fritzy image" especially the power connections for the servo, please draw your circuit with pen(cil) and paper and label all your connections.

The charging board in your picture does not have terminal labels and has allowed you to connect the servo up to the charging board backwards.

Tom....
PS If you must Fritzy, RED positive. BLACK negative/gnd

[marvinwright]

Hello,

Apologies I made a mistakes in previous reply
I also redid the schematic, hope its corrected and more clear now.

So the servo will be connected to the same out and in port of the TP4056. This means the servo and Nano are connected in parallel, hence, equal Voltage.

I will use the Vin pin on the Nano. I found it has a recommended (can handle) 7-12V input.
Reference: Max. voltage and amps for Vin to handle + best way to supply power to Arduino ? - General Electronics - Arduino Forum