Powering NANO + Bluetooth HC-06 + Servo from external source.

Using Arduino Motors, Mechanics, Power and CNC
#1

Hi guys, newbie here :slight_smile:

I’m just wondering how to power all my devices together to make my project work.
Here’s my project: An arduino Nano uses a bluetooth module to get strings from a phone and then activates a servo 9G .There’s also an LDR connected in this project.
Here’s the problem: Powering all this stuffs from the arduino micro-usb socket seems quite unreal to me. i think the current draw is higher than the amount nano could give.

Here’s my power supply hardware: a 12V DC 330mA wall power supply that i used before with arduino with no problems.
Here’s my idea : I know that nano has a voltage regulator onboard (using the VIN pin) , but i thought that 12 Volts was too much for that little regulator to dissipate. So i would use a LM7809 Voltage regulator to drop down the Vin for the NANO( who will power the LDR and the bluetooth module from that source) . And then , besides, adding another LM7805 parallel to the nano to drop down the Vin for the servo ( that has an operating voltage between 3.0-7.2V).
Do you think it could work?

Here’s a little and really simple scheme

And what about powering all with a common microUSB phone charger? (5V 700mA)

Scheme.jpg
Scheme.jpg2718×1022 92.8 KB

#2

Basically, that's sound.
Just a "heads up" for you: whatever current the servo pulls will come in/through/from the 7809.

#3

Thanks Pancake!
I was just wondering if ther 330mA that my wall adapter could give are enough....
The informations i have on current draw are:
HC-06 bluetooth = 150 mA
LDR (10 kOhm + 10 kOhm resistor, powered with 5 Volt ) = 0,2 mA more or less.
Nano running current = about 20 mA
Servo 9g Tower Pro: BIG MISTERY
I found no datasheets reporting current draw for this small servo , asking google for some informations had really different results.
Some says it draws about 50 -80 mA , some 80-100 mA, some others 200-250 mA, another google result 80-90 mA standby and 300 mA (!!!) while moving
Can someone light my mind up about this cameleon-like specs?

#4

Well, 330mA... I overlooked that.
A servo draws a lot of current when it starts moving and less when it's in motion (it's that inertia deal) and then more or less depending on the "work".

#5

Mmmmh...
I think i'll switch to a Wall -to-USB adapter and a microusb cable....this way i can get 5 clean volts and up to 700mA, with no regulators to solder and extra circuit.
Sounds also a bit cheaper :smiley:

#6