Circuit help - diagram included

[Dkendri]

Hello all. I have a project where I have to design a box that, basically, turns itself off. It is a ME project, and though I have the mechanics figured out, the electric part of it is beyond my knowledge. Here is the simple explanation. I hit a toggle switch (A) on the outside of a box, and it turns the motor on. It extends a 'hand' that comes out of the box and switches the toggle switch back down. The power doesn't turn off then, but the motor inside reverses direction, bringing the hand back in. When the hand gets back to its position, it hits another switch (B) that shuts all power off. I asked my smart cousin about it, and he sent me some info, but it is a little confusing. Here is the 'truth' diagram:

A B OUT

1 0 1
1 1 1
0 0 -1
0 1 0
A = outside switch
B = inside switch
OUT = motor direction {1 = Forward, -1 = Reverse, 0 = Off}

Okay, i actually understand this. When the outside switch is on, no matter what the inside switch is like, the motor rotates forward. When the inside switch is not pressed down, and the outside is flipped back down by the hand, it moves backwards. And when the outside is down and the inside is pushed down, the power quits.

He also sent me a diagram of the circuit he proposed to achieve the behavior of the truth table. I attached it.
His words: "Relays 1 and 4 are connected to the correct voltage for your motor, Relays 2 and 3 are connected to ground. Switches A and B should be connected to a lower voltage source (usually 5VDC) that is compatible with the electronic gates and the coil of your relays. The [BIG D] is an electronic AND gate, and the arrowhead on the connection between A, B and the [BIG D] represents NOT gates.
If you use a Double-pole, Double-throw (DPDT) relay, you can replace the 4 relays with one."

Okay: What is a gate? That is something you buy? He is saying I need a separate power source for the relays (or one DPDT) relay? What can that be? The motor I want to use is an electric screwdriver motor that uses 4-AA batteries. How do you connect something to ground? Isn't that just a piece of metal? They make all types of different relays (i've looked online); do the different ratings matter (different amp, different volts), or as long as I do not exceed it should I be okay?

If i use the relay seen here: https://www.radioshack.com/product...._name=CTLG_011_002_013_000&product_id=275-217

what kind of toggle switches and such do i need? Basically, I am not very smart in the electronics field. Any information and answers to my questions will help. Thanks for looking at my problem.

 

[eblc1388]

This is my idea of how it can be done. You would need a toggle switch with three or four pole(set) of contacts. Most common toggle switch has only one or two set of contacts. Remember to buy a switch with only two-position, as some of them are designed for three-position(center OFF).

At fully retracted position, limit switch is pressed by the hand mechanism and so in open-circuited position. Motor has no power and is not rotating.

When user flip the toggle switch, lower part of the switch contacts bridges across the position limit switch so motor gets power. The motor operates to move the hand away from its fully retracted position. Once the hand has moved away from its resting position, limit switch closes but this does not effect motor running direction.

When motor-hand reaches the toggle switch, it flips the switch to the oppositive direction. This causes the motor to reverse direction. Power to the motor is now maintained via the limit switch as toggle switch contact became opened.

Motor-hand continues to travel in reverse until hand moved into final resting position and operate limit switch to cut itself off.

If the current/voltage of the motor is too high, then you can replace the connection by two additional relays as shown. In this case, you can use different power supply voltages for that of relays and motor if you wish. But the first circuit is good for a screwdriver motor.