Some logic questions here. Seems more like a riddle....
There is one particular sequence driven by a transmission I made. The sequence uses gears to move a cartridge up/down via tongue/groove. On the cartridge you can see there are 3 dimples. I'm planning to use the concept of a Spring Plunger to hold the cartridge in 3 different locations. You can see the spring pushing the metal ball down into one of the 3 dimples. I am using a Nema17 for the transmission motor. You can see there is an optic sensor at the top for determining when the cartridge is up all the way.
Dimple 1 is down and connects the cartridge to an assembly.
Dimple 2 is in the middle of assemblies.
Dimple 3 is up and connects the cartridge to another assembly.
How could the system automatically detect and know which direction to go to find home, Dimple 2? For example, In case a power failure, or a sudden stop the system would need to recalibrate somehow and ideally go home to Dimple 2 which would then avoid any collision with the other assemblies in case they start moving. But how would it know which direction Dimple 2 is?
I was thinking 2 sensors, maybe 3 but can't figure it working. I thought of maybe using an SG90 servo which could detect/remember positioning? is this right? but I was hoping to only use the transmission Nema17 motor to move the parts with some sensors instead of an adding a servo. Is this possible somehow? How could you go about homing this?
Seems like a photogate or single limit switch could solve this. Move to one end until you trip the sensor and then you know exactly where you are and can move back to wherever you want to be.
In the absence of a reason not to do so, the home switch is typically at one extreme of travel for exactly this reason: on power failure/startup, the device always knows which direction to go to find home.
thanks Delta and Cedar. Yes, I could home it on either end but at that point the assemblies are in conflict. For example, if I home it up, the mating assembly may not be low enough (because it too moves up/down), there may be a collision. You are correct, It is more common to home it on either end as opposed to the middle.
But I'm wondering if there is a way to home it to Dimple2, in the middle?
Maybe I'm just complicating things but space is very limited on either end.
You'd need a photogate on either end set so that if it is in dimple 2 then neither is tripped but any movement either direction trips one.
It might make more sense to think about the order of operations at bootup so that things always make sure they get out or each others way. Bootup for some devices is a delicate dance.
I used to work on a system that had multiple two-axis gantries where the Y-axis moving when Z was down could cause something to break. Solution on power up was to home all the Z axes and only after they were successfully homed, then home the Y-axes.
