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Beginner's Guide (Inputs)

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DaOld Man:
There is a function that Mrotate has been able to do in all versions. This function is optional so you dont have to use it, but it can be handy.
This function turns the monitor off while it is rotating.
Whats the advantage of this? Well as was discussed in the previous post, turning the monitor off while it is rotating may do away with the need to degauss the monitor, since most PC monitors (CRT) automatically degauss on power up.
MRotate turns on a printer port output which you can wire to relay. The relay turns off the power to the monitor.
When Mrotate senses that the monitor has reached it's destination, it turns off the output, which turns off the relay, which turns the power back on to the monitor. The monitor automatically degausses and you are playing without the screen being skewed or mis-colored.
To do this, you will need a relay with a normally closed contact (N.C.)
This means when the relay is turned off, the contact is closed. When the relay is turned on, the contact is open.
The relays contact must be rated for the voltage of the monitor (120 AC in US and 220 AC in the old world). And it must also be rated for the current that the monitor will draw. (A 10 amp contact should be good.)
This contact wires into one of the power wires going to the monitor.
The relay will also have a coil, that when energized (or turned on), will open the contact and turn off the monitor.
Here is where it gets a little tricky.
Since I have not been able to find a solid state relay (SSR) with a normally closed output, you will have to rely on a relay with a coil.
Now since most relays coils draw more current than the printer port can put out, you will need to buffer it with a transistor. You can also use an opto isolator or even a SSR to turn the relay on, instead of the transistor.
(see diagram below)
If you are not using the printer port, or the software you are using does not support this feature, and you are not controlling the speed of the motor, you can wire a relay in parallel with the motor.
The voltage of the relays coil must be the same as the motors voltage.
This way, when the motor is running, the monitor is off.

In earlier versions of MRotate, I called this function the "Monitor Off Relay".
But in MRotate3, I called it the "Kill Monitor" function. (Kinda like "Kill Bill", only different;)
I may have slipped up on some of the help files in MRotate3 and called it monitor off relay, but I think Kill Monitor is a better term, dont you?

If you are using an LCD monitor you may not want to use this function, but it is there if you want to use it.

DaOld Man:
With MRotate3, I added another option. This option is for a brake.
Why would you want a brake?
Well, if your monitor tries to turn back to horizontal after the motor turns off, you may need some way to hold it still.
Some motors have a built on brake, which when power is supplied to a coil on the brake, two plates separate, which allows the motor to turn. When power is turned off from the coil, the brakes are returned to the touching position by a spring.
This stops the motor, or at least makes it very hard to turn.
This type of brake is called a friction brake.
And when the coil of the brake is turned off and the plates are touching, it is called "set" , and when the coil is turned on and the plates are separated by the magnetic pull of the coil, the brake is referred to as being "released".
In the first picture below I show a stepper motor that has a brake attached to the end of the motor.
The motor has a gearbox that increases the torque and decreases the speed, but when the output end of the gearbox is turned, it increases the speed of the input, or motor end of the gearbox. The torque is greatly decreased too, so the brake doesnt have a very big job of holding the motor end still.

But what if your motor doesnt have a brake attached to it?
You can still use a solenoid to apply a friction type brake to the monitor disc.
See Figure one.
This figure is pretty general, but it should give you an idea what Im talking about.

There is still at least one more option, which may be simpler.
Instead of a brake, you can use a solenoid to lock the disc in position.
Look at figure two.
The solenoid, when energizes, disengages the plunger from the notch in the disc, unlocking it and allowing it to turn.
One of the disadvantages to this type of brake (actually a lock), is that if the motor stops between 0 and 90 degrees of the disc, you wont have any braking action at all. However you can design your rig to allow the plunger to engage when the notch is aligned with the plunger. (Notice the beveled edges of both the plunger and the disc notches in figure two.)

DaOld Man:
Ok, I drew a quick diagram of how you would hook up the brake circuit.
Of course you will need a power supply for the brake, a transistor to switch the high current of the brake, a diode to protect the transistor from voltage spikes from the brake's coil, and a current limiting resistor to couple the transistor's base to the printer port output.
The transistor needs to be NPN, and it needs to be rated for the amount of current the brake coil will pull.
Also, the transistor you use may not match the lead orientation I show in my simple drawing. Just connect base to printer port (through the 1 K resistor), emitter to ground, and collector to the brake coil and you should be ok.

In the attached drawing, I have on top the component layout, trying to make the circuit look how it would in real life.
Below that is the schematic diagram, showing symbols instead of drawings of the actual devices.
You should now understand why I use symbols, they are much easier to draw and look a lot neater. you just need to know what each symbol represents.

About the circuit:
When the printer port output is low (ground) the transistor is turned off. No current flows between emitter and collector, so the brake coil is not energized (turned off, or set).
When the printer port output goes high (+5VDC), the transistor turns on, and current flows between emitter and collector, energizing the brake coil (turning it on, or releasing it.)
The 1 K resistor limits current flow on the printer port output and diode D1 protects the transistor from spikes when the brake coil turns off.

Next post I will duplicate this same drawing using a solenoid instead of a brake coil.

DaOld Man:
Here is a diagram showing the same hookup using a locking solenoid instead of a brake.
Notice the only difference in the schematic diagram is the symbol for a solenoid. It looks like a tilted Z, and it is the symbol for a solenoid coil.
Notice also that the diode is still needed on the solenoid coil to protect the transistor.

DaOld Man:
Dont want to use a transistor? You can use a SSR (Solid State Relay) to turn on the brake or solenoid.
This drawing shows only the schematic.

OK, I think I have pretty much covered the brake.
Remember, first decide if you need to use a brake or lock. If you dont need it, then dont waste a lot of time and energy (and money) on it.
But if you do need a brake or lock, then you now know that it is possible.

Lets move on to Inputs.

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