I'm looking into building a smart blinds system to hook into a controller. My proposed main components are
Arduino mini pro 3.3v or 5v
Servo 4.8-6v
NRF24L01+ 2.4ghz RF @ 3.3v
3/ 4 AAA NIMH 1100 MAH batteries @ 1.2v per battery. AAA Batteries are chosen as a design choice as they are small enough to be hidden behind the blinds and easily accessible for replacement if required.
The RF unit will communicate to a 2.4ghz unit on a raspberry Pi.
So my requirements are:
The system works for at least a month on Battery. Ideally as long as possible.
RF control of MCU to get the servo to go to 2 options - Open/Closed. This will be used a minimum of 2x a day. With no maximum use. I understand that using the servo more will reduce battery life.
I am torn between this setup:-
3 batteries @ 3.3v Setup with MCU and RF with a step up booster to power the Servo when required.
4/5 batteries @ 5v Setup With MCU to power servo and step down converter to power RF unit.
I think you will need the higher voltage to operate the servo so a step-down for the nRF24 would be appropriate.
For this application I'm not sure if a servo is the best choice unless you plan to include a system (a relay or a transistor) to shut off power to the servo. And if you do that I don't know if the servo will be able to hold position.
A DC motor with a worm gear drive will hold its position without any electricity. It may also be possible to choose a motor that works adequately on 3volts.
You must keep in mind that raising a blind can be hard work and may draw heavily on your batteries even if it only happens occasionally. You probably need to experiment and measure the current draw before you can tell how many movements can be obtained from your batteries.
Robin2:
You must keep in mind that raising a blind can be hard work and may draw heavily on your batteries even if it only happens occasionally. You probably need to experiment and measure the current draw before you can tell how many movements can be obtained from your batteries.
...R
Robin, it may be that the blind doesn't have to be raised, but instead rotated to open/close.
That would explain why Kenny has chosen to use a servo motor as the motive power.
Yes, I'm only looking at a servo to rotate the metal bar in a set of Venetian blinds. Already built a mechanism to connect the servo to the shaft and have demonstrated a prototype using a arduino uno and either a usb battery pack or 4 AAA batteries. As there are no weights to hold I have no issues using a standard servo.
note apologies for not responding sooner, I wasn't expecting such fast response on the forums
