Hello everyone,
I wonder if anyone can give me some advice please.
I am planning a sculptural work which requires a number of elements to move forward when someone walks up to the work, around the 3m range. I was planning to use a normal IR sensor to trigger the movement and sound.
Now all of that seems pretty straightforward, however, the bit that I’m struggling with is the pushing movement towards the viewer from the frame. I first thought of linear actuator type of thing but this would make the frame really wide. The idea is the wall hang the work.
Then I thought of using compressed air pistons, but they will probably be too noisy.
They don’t have to move that quickly, up to 1 sec to fully extend forward to say around 12 cm.
I also considered some sort of push rods or stepper motor with a gear head that pushes forward like a worm drive?
So basically would like a wall mounted box with a minimum width that contains a mechanism to push around 5 elements forward.
IS this a one-time movement, or will they need to return to a resting position? ANY piston moved by a fluid(air or oil) suffers from "sticking" where much more for force is needed to begin movement than is needed to continue movement, so movement will be "jerky". Then you need to reverse the direction.
Consider all the moving parts are attached to a panel with locating guides that will hold the moving pieces and move them all together towards the viewer. Only a single prime mover will be required.
What is your mechanical construction and shop ability?
Thanks for your suggestion Paul, yes they will need to return and all five elements will need to individually at different times. I have pretty good shop skills as I teach 3D workshop at a local college.
I’m thinking of using a worm drive motor as I can reverse it, with two guiding runners on each side for each one mounted on a frame. To keep the size down I’m thinking of having the threaded rod go into the objects but have the nut assembly at the bottom of the thread for maximum extension if that makes sense?
I can purchase quite cheaply on Amazon the following 300rpm in 6v or 12v not sure how quickly that would move and which voltage is most suitable for the Arduino?
Old floppy disk drives have steppers hooked to a linear leadscrew. About 1" of travel.
Servo mountd on side with arm can rotate 90° and raise up.
Solenoid with bellcrank (L shape with pivot at junction) can raise an arm with a pull. Long wire to end could allow mounting at edge of frame with actuator arm in center.
10cm ~4", no biggie for bellcrank & solenoid (sudden motion) or servo with 4" arm (slower but controllable)
Leadscrew takes 2x travel, 1x in front, 1x behind, follower. McMaster sells leadscrew assy's and all sorts of industrial actuators. But for this i figured chesp & easy - nothing you can't 3D print & build out of cheap hardware. sg-90 (?, commonly found in lots of Arduino kits) servo with arm can move 4" depending on load.
I originally thought of a servo but as the elements I want to move need to push into a latex far enough to see their shape min 100-150mm I don’t think a servo would be strong enough. I need variable travel each time to create variety so solenoid is out.
I like the leadscrew assy's tip, for a faster travelling thread, I’m based in the UK and found these on eBay, but how do you rotate them with a motor ?
I wonder if you can get them with a gear attachment or build in motor?
There is a shaft coupling on the leadscrew (that cylindrical bit on the right end) that will easily attach to any motor with the correct sized shaft. The particular couplers shown will allow for slight shaft misalignment. Again a 3D printer can solve a variety of mounting issues.
You're going to want to have a zero (and maybe max) travel limit switch(es). Otherwise after a power blip during motion, you'll lose reference and index the follower into the end block or completely off the leadscrew.
OR you can eliminate the far end bearing by using concentric tubes. The inside tube is fastened to the nut and the outside tube is fastened to your framework. The inside tube will do the pushing.pulling on your stuff.
Standard lever micro switches are common and cheap.
More reliable, and slightly more expensive, are optical interrupter modules.
Both are available with a variety of actuators and mounting configurations.
I must say I’m really impressed with this forum, some really good advice, thank you.
Could I possibly ask if someone could list out the electrical hardware/parts I would need?
as a few parts have been mentioned that I have not even considered.
Im using a Mega and as a reminder wanting it to trigger when the viewer comes up to the wall mounted work in the 0-4m area, would be useful if there was a way to give a different response the closing the viewer got to the artwork rather than a simple switch on and off.
The trigger would move the elements we have already discussed forward 100-150mm.
This movement will need to vary so as not to repeat the same pattern each time (within reason) and play different sound options (spoken word) again would be wonderful if this could vary depending how close someone was to the work.
All parts to be contained within the wall mounted box.
I am confident about the metal shop work it’s the electricals I don’t have the expertise in.
I have not mentioned anything about code yet as I was thinking about tackling this after I have a mechanical solution then work to control it. Is this the best way to start a project like this? I can’t think how you would write code if you don’t know what you’re using?
The sonar module gives distances so you can change actions based on distance. LDR's can sense shadows. PIR sensors trip when a warm body is sensed. A mat switch can trigger when someone steps on it. Sounds, vibrations, etc can also be sensed and reacted to in real time. Here is a "busy box" that does all sorts of crap.
One small step at a time is necessary in order to make your project work. You have never mentioned the power supply for your project, but will need to consider them soon. As far as "code", you cannot develop a step at a time without writing code to test each step. By the time for the final project, you will be an expert on all the subsystems!
