DC Stepper motors/Rotary actuators/Solenoids power requirements for low voltage systems

Thread Starter

GC302

Joined Sep 28, 2021
4
Good morning,

I'm new to the forum and I'm here specfically to ask for your advice and/or suggestions. I'm trying to design a system to control a flow of very slightly vacuumed air to a sensor through filters. This is to measure air quality in the ecosystem local to my device to quantify the presence of gases.

Currently there is only one filter in the system and I'm trying to figure out a way to introduce 3 or 4 filters in a 'bank' of sorts to be switched in and out as the previous filter degrades to extend the time between maintenance.

I've designed a kind of circular labyrinth of sorts that will be 3D printed that will guide air from the intake to an output towards a filter, and when rotated will then guide the intake to another output (and then again to a 3rd output) without any 2 outputs being used at the same time.

Where I'm struggling is to consider a component to rotate this labyrinth to allow the active output to change.

My system is powered by solar power and has a limit of 12V DC, the entire system without a motor uses about 8-10W of power and I'd like to use a motor or actuator that can be powered up to rotate the device and then be powered down. The output would be changed roughly every 6 months or so and to that end having a continuous current draw for 6 months isn't ideal when it's not being utilised.

Originally I was looking at 12v latching solenoid valves to switch the air in and out as that would avoid contamination of the air through leaks however there isn't any kind of product that can meet the needs I'm looking for.

I'm aware this is very niche so again any advice would be appreciated. I've attached 2 crude drawings to show what I'm trying to design. Any suggestions at all on ways that it could be done using very low voltage (12V DC or less), latching solenoids/pinch valves or motors or anything would be great.

Thanks,
George
 

Attachments

Sensacell

Joined Jun 19, 2012
2,908
You don't say much about the details- like reliability, cost, size, weight etc.

A kind of simple solution might be a hobby airplane servo.

You could make a valve with 3 positions, have the servo move to the indicated position, then power it off.
These things rotate through about 190 degrees, and can be positioned accurately, but are not very repeatable unit to unit, so you might need to calibrate it in production?
Zero power when idle.

As long as the valve has little or no back drive force, the geartrain friction would hold it in place.
Obviously not good for high vibration environments, it might move on you.
 

Thread Starter

GC302

Joined Sep 28, 2021
4
The systems I'm maintaining are in remote locations across the globe so reliability is mostly focused around weatherproofing although they are inside a metal box housing. I'm not expecting robustness like you'd see in military aviation grade and I'm not expecting any kind of external interference except perhaps curious animals.

The air is being drawn through 6mm OD, 4mm ID sort of medical tubing.

Cost wise the reason for this system expansion is because it's not feasible to fly out to Australia from the UK every 6 months to replace these £70 filters so I believe up to £200 is probably a good place to start. Weight isn't necessarily an issue although size is, the housings that the systems are in can be as small as about 300mm x 300mm x 200mm and there are other components in there.

Would you be able to provide a link to an example of a servo? They sound like they could be ideal.
 

MaxHeadRoom

Joined Jul 18, 2013
23,805
For a controller you could look at a Smart Relay, there are a few manuf. of these, they also come with a 24hr clock which can be utilized by timers, if necessary.
 

Thread Starter

GC302

Joined Sep 28, 2021
4
There is a logger for collecting and processing the data at the heart of the system which can be signalled remotely via GPS or SIM (or programmed in before it's installed) and that is what's going to switch the filters in and out every 6 months
 

KeithWalker

Joined Jul 10, 2017
1,947
The simplest solution I can think of would be like the rotating magazine of a revolver, rotated in steps by a ratchet and solenoid.
 

Thread Starter

GC302

Joined Sep 28, 2021
4
I did think about something like this but the issue comes with making it air-tight so the other filters aren't being used at all until they're selected in
 
Top