Thread: MITB shutoff problem

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im finishing up my monster in the box and everything was looking really good. got the motor working and the controller and sensor hooked up with animation and almost audio and i go to try it out and the motion works fine but i cant help to see that it doesnt always end closed. sometimes its half open when its routine is up and sometimes it doesnt. can anyone help me with how this can be fixed?

It is a bit hard to answer a question like this without knowing how your prop is designed, but since you mention a motor I will make some assumptions.

You are using motor like a wiper motor to move a arm or rotate a cam that opens and closes the lid. The problem is that the routine stops and the motor sometimes stops with the lid open.

So the easy answer is a parallel circuit. If you are using a DC or an AC motor it really makes no difference. You just need a micro switch that can handle the voltage and amperage of the motor.

Now I could get fancy and ask you to mount a cam on the motor. That is the way I would do it. But you can also mount the micro switch just below the lid somewhere and add a small block that when the lid is open will allow the micro switch to open. When the lid is closed you want the block to close the switch.

You will take a lead from your power source to the common on the switch. Then from the normally closed side of the switch you will take a lead to the same contact on your motor that your prop controller lead goes to. This is easier to explain with DC. So lets say you have a battery. The negative of the battery is attached directly to the motor on it's negative side. The positive of the motor has two leads attached. One that goes to the relay on your prop controller and the other goes to the normally closed side of the switch. The common on the switch connects to the positive on the battery. The positive on the battery also connects to the source voltage for the relay on your prop controller.

So how does it work?

When your routine starts the prop controller closes the relay which routes the + from your battery to the motor and the motor rotates. But when the routine stops there is no way to know where the motor will stop. But with the addition of the switch, there is now a second path for power to the motor that will only be available when the lid is open. It does not matter that the motor is getting power from two different paths during the time the door is open. One bit of caution. Make sure you do not reverse the polarity between the two circuits. That would be very bad and you can expect smoke. LOL !!!

Hope this helps. Oh and be clear on the normally open NO and normally closed NC. Micro Switch when the tang is up completes the circuit between common and the NC connection. When the switch tang is pressed down the circuit is now complete between the common and the normally open. So if you miss wire this, then you would see the prop shut off and continue to run until the door opened. Then it would shut off. Exactly the opposite of what you want.

Yep, that'll work. I was going to suggest a way to index the motor rotation, but for a MITB this is a great solution.

I was thinking if the motor had a "park" position on it just end it with that command. Most WW motors have a park position.

You would likely use a circuit I know. I am guessing an encoder to offer a home signal?

If you can design something, I am sure we all would appreciate it. I think more and more people would like to use motors instead of pneumatics, but as you can see without some kind of continuation circuit, the effect can be uncertain.

I went low tech cuz I don't know how to design circuits. Wish I did.

That's a good point. Maybe missing something here. I suspect the parking circuit on a wiper motor mimics my micro switch idea. I bet if Chris checks he will find another wire that if he attaches the hot lead to it the motor will run to a park point.

Good catch Scary. Of course we need to know if the motor he has is a wiper motor and it has a park circuit.

Chris,

If you can locate the park circuit, then the best option is to run a lead from the NC on your prop controller relay to the park circuit. This way when the prop controller deactivates the relay the NC will provide power to the park circuit and the motor will continue to rotate until it hits the park switch. The only thing we do not know is if you are using a wiper motor that has a park circuit. Then all you need to do is mount your actuation arm so the door is closed when the motor parks.

The park feature cuts you off after a single rotation, unless you can figure out a way to override it. Spinman's solution will allow the motor to rotate as long as you need it to. I use the dual power source trick on my coffin lid motor - works great.

Spinman, I do have a circuit that uses a snap switch as a crude encoder, allowing 180° rotations and letting the motor go to a home position when the cycle is complete.

hmmm this is foreign to me! LOL
okay what am i looking for on the wuper motor its one from monster cuts and there are only those 2 wires that come out?

Just use my solution. It is the easiest way.

Just place a micro switch as I indicted and wire it using the NC side of the relay. So on the NO side the wire goes directly to the motor. On the NC side the wire goes to the common on the switch and then a wire goes from the NC on the switch to the motor. Same connector that the NO from the relay goes to.

When the relay is on the NO side will close and the prop will run. When the prop shuts off the NC side will be hot and it will provide power to the motor until the lid closes.

Simple and easy to set up.