Total Newbie on a budget

[bitternboy]

If you're keeping it simple and using a single switch for the weapon then a set of RC switch + relays would do fine (plus some microswitches for end stops if the LinAc doesn't have a limit switch of its own) to just flip it between the battery voltage in either direction. You'd have to do some simple circuit design to get the receiver signal controlling it properly.

Alternatively, you could get a reversible brushed ESC but if your not worried about controlling the speed then you'd be wasting some functionality.

[bitternboy]

If what you salvage from the mondeo has some sort of end stop switches then possibly (assuming it's a suitable motor :P)

Bare in mind you don't just need physical end stops that stop the motor turning, they need to actively cut off power supply to the motor in their respective directions when the limits of the lin-ac are reached. The controller won't know when to stop on its own and will stall the motor at the limits of movement, which you don't want.

Lots of off the shelf lin-acs have this built in so you can drive them against their limits of movement and they won't stall, a bit like this:

[RogueTwoRobots]

They're just two microswitches, and each has a diode connected to it. This allows power to travel in one direction only. The idea being that when something reaches the end of its travel, it hits the switch which cuts the power to it, thus protecting the mechanical bits. But it only cuts power in one direction, allowing you to reverse/retract the motor to reset or reposition it. A microswitch at the other end of the travel will cut power there too. I fitted these on my featherweight grabber bot and they worked pretty well.

[bitternboy]

That diagram shows the typical set up for using switches at the ends of travel to stop current flowing and letting the motor push it any further, sorry for being confusing :P

The ends with V+/- are the voltage you would be supplying from your ESC. The things labeled "NC" represent switches that are activated when the limit is reached, one for each end; NC stands for normally closed, so when it hits the end, they are opened.

The components represented by the arrow and line are diodes. Their function is to only let current flow in one direction.

The M in the circle is the motor driving the lin-ac.

Imagine the lifter is halfway up. Both switches are closed, so the diodes are redundant/bypassed and current can flow in either direction i.e. you can tell the ESC/relays to provide a voltage across the circuit in either direction and the motor can spin in either direction, raising it up or down.

Now the lifter hits the top of it's path, you don't want the motor to try and keep pushing because you'll break the mechanism or stall the motor. One of the switches is at the extreme however and is activated/opens. This means that if current wants to flow through the circuit it has to bypass the switch and flow through the diode instead of the switch. The diode won't let current flow in the direction that would result in the motor trying to push the lifter beyond its limit.

The other switch is still closed so it can still move back.

The same thing happens with the second switch and diode for the other limit.

Hope that's more helpful.

EDIT: Ah, got beaten to it :P

[R9000]

You do need diodes here, because otherwise, your linac will disconnect permanently when it gets to one end. Think of it this way: The diagram Bitternboy posted shows a circuit where there are two one-way paths for the current to follow, and a path for current to flow in either direction (if both switches are closed). Now if one switch opens (or disconnects), the current can only flow one way through the circuit now because the current is now forced across the diode that is connected over the switch. This means that, while the circuitry will stop your motor from trying to push the linac past its limits, it will still allow current to flow in the opposite direction so you can retract it.

Your diagram would stop the linac moving completely since it pulls both contacts of the motor to the same voltage, which then stops it (I think). You basically just need to make something like Bitternboy posted. The diodes you need can be fairly basic, you just need ones with a higher reverse voltage than you're running your motor at, and some that can handle the current through it (which you can measure while it's running). Also keep in mind that diodes introduce a small voltage drop when used (usually around 0.7-1V) but as long as your linac can move off the limit switch again, it'll be fine.
Something like this should do, but check your voltage and current as I said: https://www.arrow.com/en/products/1n...FQMM0wodY6MGTA

Oh, and don't get Zener diodes. They're not what you need here.