Advice on battery power supply. FS5106R , SM-S2309S, nRF24L01

Hi all,

I am working on a project with Arduino, 2x servos - FS5106R and SM-S2309S and 1x nRF24L01 Transceiver. Apart from doing the projects coming with the Arduino starter kit I don’t have much experience, so consider me as a beginner.

More information on the project: Essentially I am designing a sort of harmonograph, which needs to run on a battery for max 2 hours. I am using a nRF24L01 Transceiver to receive data from a gyroscope and control SM-S2309S servo, while other FS5106R will be running continuously at the same time at very slow speed (controlled by potentiometer) and nothing heavy would be attached to it. After reading various posts I understand I shouldn’t run the servos from the arduino, but external power supply and this is where my trouble comes.

I would appreciate if anyone can advise me on what battery power supply to use. A schematic diagram is attached to show the system.

The requirements are:

  • be able to power the system (both arduino,transceiver and servos) for at least for 1 hour.
  • be able to deliver power in case SM-S2309S is later replaced by FS5106B servo. Therefore having 1x FS5106B and 1x FS5106R.
  • Smallest size is preferable.

I am happy to provide extra information if needed. Thanks in advance.

Image from Original Post so we don’t have to download it. See this Image Guide

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If it was my project I would replace the Uno either with a 3.3v Pro Mini (I don’t know if there are 3.3v Nanos) or just an 8MHz Atmega 328 on a piece of stripboard and then select whatever batteries you need for the servos and use an LM1117/LD33 3,3v regulator to provide power for the Arduino and the nRF24.

If the servos need 6v it is not so easy to drop from 6v to 5v for an Uno - though a couple of silicon diodes in series (giving a drop of about 1.2v) may be suitable.

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I should probably mention I have a powerbank available, which has 5V /2A output (if label is correct). However, I don't know how (scared to experiment) to connect it to a breadboard so it can power both the servos and the uno.

PS. Note taken regarding the image attachments.

If you have a 5v power source then just connect it in parallel to the servos and to the Arduino.

If you post a diagram (a photo of a simple pencil drawing will be fine) showing how you think they should be connected we can look at it.

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It's not the best diagram, but I guess it summarizes the options I have considered so far ,because of what I have in hand.

Option A (powerbank): I am not sure how safe this is. Don't really want to damage any of the components

Option B (9V battery & AMS1117-5V): The output provides only 700mA (as far as I know). Would that be enough for 2x servos and 1x Uno?

As far as the Arduino is concerned I don't see any difference in the two options in Reply #5 - but 700mA is unlikely to be sufficient. Better to budget 1 amp per servo - more if they are powerful servos.

I am assuming the power bank produces a regulated 5v output.

What sort of 9v battery are you thinking of?

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A. I am not sure if the powerbank produces regulated or unregulated output. This the model I have -Canyon CNE-CPB100W.

B. Regarding the 9V battery, I was looking at standard (square) 9V or 6xAA (which should last longer).

C. If I consider the option to use 3.3V Arduino as suggested previously how are things going to work in more details? Can I use 6V (4xAA) battery to power directly the servos and drop the voltage down with AMS1117-3.3V (found on-board on the YwRobot Power supply) to power the 3.3V Arduino? And what about the 3.7V required for the nRF24 module or using potentiometer? If this how things are going to work I am okay doing that, but the problem is ordering and getting on time new 3.3V Arduino and new components in general due to Christmas holidays, as my deadline for the project is first week on Jan.

Btw thanks a lot for the help.

Referring to Reply #7

A. if the powerbank is for connection to a USB input it will be a regulated 5v.

B. a PP3 type 9v battery would be completely useless. They cannot provide enough current. 6 x AA cells should work for a time

C. I have some nRF24s and Atmega 328s running off a pair of AA alkaline cells without any problem - i.e. 3v or a bit less is perfectly adequate.

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Just to recap.

A. It is safe to power the system with powerbank 5V/2A output via stripped down on one end USB cable to be plugged to breadboard.

B. 9V from 6xAA batteries should work for a short period ,but the AMS1117-5.0V would limit the current to 700mA , which is unlikely to be sufficient for the 2x servos.

C. 6V from 4xAA batteries can power directly the 2x servos and the AMS1117-3.3V (on the YwRobot Power supply) can drop the voltage for 3.3v Pro Mini, but again this should work only for a short period.

Given these options ,if I am correct, then the best option is the powerbank. I am not missing anything right?

cecoka: Given these options ,if I am correct, then the best option is the powerbank.

That is my view, yes. It is certainly the simplest.

However I have not taken account of how much stored energy the powerbank has, whether it can be recharged, or whether the 4xAA cells would be a cheaper option. You can get rechargeable AA cells - though 4 NiMh cells would only produce 4.8v. I guess you could use 5 x NiMh cells for 6v.

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