Levelling mechanism for work table, how do I wire 4 linear actuators to operate independently?

Total newbie here, so thank you for your patience.

I am building a moveable table for my table saw, but my garage floor is very uneven. My plan is to install 4 linear actuators to level the table over the floor. All 4 linear actuators need to operate independently and at the same time. Because I’ll be moving the table to different locations in my garage I need to control each actuator independently so that it can lift and level the table over differing heights in the floor.

Ideally I would like the setup to be as follows:

What I need to know is:

I’ve attached a circuit diagram of how I think it should go. Please let me know if I’m going to burn my garage down with this!

Thanks in advance!



Problem: Uneven concrete floor for table saw that weighs over 50 lbs. When it wobbles it doesn't perform well.

Idea: use motor actuators with position feedback to balance weight on each leg so it is stable.

Problems:

How can you sense position or balance it level or have even balanced weight and be level?

How can you design 4 servo error drivers from those "sensors" to null the error in each so they match?

How much floor imbalance do you have? 1" 2" 4" 8"

How much power is needed to drive the max weight on each when it starts unbalanced on 3 legs? How about using 3 legs instead then it will always be stable. Then use a 1'x1' plywood with 2x4s to make a footing for leg(s) to make it more stable OR use Leg screw levellers ( Use threaded bolts like a washing machine for 2 legs)

How many times per day or how long must it take to level and stability to meet your expectations?

How about long 1" x 4" x 1' tapered wedges to balance 2 legs so the table does not slip. Use a hammer to adjust. There are even better ones with telescopic slide and lock feet. Or use 2 little inverted hydraulic jacks fastened to the table. Pump and lock... done.

If there is a simpler mechanical solution that meets your requirements, make it so. A 50W linear actuator won't be strong enough and very unstable with dynamic loads unless the force is 10x the weight with a well-designed servo or a gear motor.

Why get fancy with a servo linear actuator when you haven't thought of all the problems?

The best Design Engineers research make or buy solutions then write specs and iterate until it is "perfect", which just means meets or exceeds expectations.

"Make or buy" "Slightly ahead of time and lowest cost"

how do I wire this together? I will attach a diagram on how I think it should go.

Except for the indicator lights, you're good to go (more on that later)

is a 50 amp power supply overkill or would it even work with a 110v plug?

It depends on the nature of the supply.

When you buy a motor rated at 8A, that means it'll draw 8A at its rated load, after it's going full speed. Before it gets up to speed it'll pull more current -- this is known as "inrush current". If it's listed in the motor specifications at all, it'll be listed as "stall current" or "inrush current". An 8A motor may well draw close to or more than 50A of inrush current.

When you buy a power supply rated at 50A, that's the current that it can deliver when everything has settled down. Different supply styles can have dramatically different response to temporary overloads -- and motor inrush current is most definitely a temporary overload.

If you're buying a switching supply, then you'll have a little brick a few inches on a side, and the thing will either shut down or outright die if you ever pull more than 50A from it. If you're buying a linear supply, it'll weigh about 15 pounds, it'll be nearly a foot in at least one direction and at least six inches in the other two, and you'll probably be able to pull 200A or more from it, briefly.

So figure out what your worst-case inrush current is, by looking at the stall currents of the motors.

If you have a switching supply and too much inrush current, you can limit the inrush current with a series resistor in series with the supply (or individual ones on each motor). Doing so will make your motors wimpier, but this may not be a bad thing (more on this later, too).

with the indicator light I assume I need a resistor on both sides of the light.

Nope. Just one. Resistors resist no matter what the direction of the current flow may be.

Amazon lists the lights as being 20mA/ 1.1-2.2V, so I’ve calculated a resistor of 490 ohms, and I’m guessing I need one on either side of the LED so that the polarity can be reversed.

What you do need is to put the indicator light (or lights) in parallel with the motor (after, not before, the switches). Where you have the thing now it'll always come on in the same direction no matter what.

If you're using a red/green LED, then what you have (with one or two resistors) connected in parallel with the motor.

As a side note, if you use a red/green LED, then about 6% of owners of Y chromosomes (and about .004% of owners of X chromosomes) won't be able to tell the color difference. If you want to be nice, use individual red and green LEDs connected in anti-parallel:



simulate this circuit – Schematic created using CircuitLab

What sized wire do I need? Is 6 aw

This is an astonishingly complicated subject if you want to get "just the right wire" in there. I suggest that you do a bit of web-dredging and find the recommended size of wire for automotive applications, for 10A on the motor side of things and 50A on the power supply side.

Lastly, should I be integrating a fuse or a circuit breaker into this circuit?

It depends on the power supply. If it's current limited (because it's a switcher) or has a fuse on the output side (likely if it's linear) then no, you're fine. If it's a linear supply and it's not fused for 50A, then yes, find a fuse or fusable link.

It's not bad practice to fuse each motor circuit for the size wire you use -- 50A is a lot, and if a motor were to short-circuit then you could easily smoke a wire that's intended for 10A. If that happened in an environment with a lot of flammable stuff around (like, say, sawdust) it could spark a larger fire. Personally I'd get 10A automotive fuses (and maybe an automotive fuse block) and use that -- or I'd get 10A automotive fusable links (they're basically short sections of special wire that act like fuses). Fusable links will be easier to install but more of a pain to replace than fuses, but they'll keep your saw from burning down just the same.

A downside to your whole approach is that you're using 10" stroke actuators, a control method that makes it hard to move them just a teeny bit, and you have a problem (getting all four feet matched to the floor to within a fraction of an inch) that requires them to move a teeny bit.

Remember when I said "more on that later" to resistors in series with the motors? If you put resistors in series with the motors to limit the current to 8A when the motors are shorted, then the motors will deliver much less stall current than normal. This means that when you're driving a leg into the floor with little blips of a switch it will slow down with greater load. So putting a resistor in series with each motor may be a good thing.

The downside is that if you use, say, a 1-ohm resistor on each motor, then you'd either need a resistor on the order of 100W (150W if the motor were a short circuit), or you'd need to get something smaller and remember not to lean on the switch once you're grinding a leg into the ground. 100W power resistors are expensive, even if you luck out and find something surplus.