# Turning head with electric motor help needed



## Mazz (Jun 24, 2007)

Hey folks, for next year I'm looking to build a prop that has a head that moves from looking straight ahead to turning ninety degrees to the left. For this I'd like to use either a reindeer motor or a wiper motor. This will not run constantly, it will be triggered using a motion sensor. Where I'm confused is how to make to motor stop at ninety degrees and return to looking straight ahead, plus how to do the linkage.
Thanks for all your help,
Mazz


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## halstaff (Nov 18, 2009)

Check this out - http://www.hauntforum.com/showthread.php?t=15212
I've used this a couple of times and it works great.


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## toozie21 (Aug 23, 2012)

halstaff said:


> Check this out - http://www.hauntforum.com/showthread.php?t=15212
> I've used this a couple of times and it works great.


I seem to miss the the link in that thread after two perusals, can you point me to "Jeff's" site where he sells the boards? Thanks!


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## halstaff (Nov 18, 2009)

Here is the link to Jeff at Simple Circuit Boards - http://www.simplecircuitboards.com/
Jeff hasn't updated his site for a while now. Just ask for the wiper motor controller circuit and he'll know what you're talking about.


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## Otaku (Dec 3, 2004)

I'm not sure that the wiper motor circuit will do what you need. The circuit doesn't actually reverse the direction of rotation of the motor (polarity flip), it just pauses halfway through the 360° rotation to hold the coffin lid open for a few seconds then continues rotating in the same direction back to the home location. The head of your prop could be stopped at the 90° position by installing the proper limit switch actuator, but the head would still rotate the full 360° when going back to the home position. To reverse the polarity you'd need a couple of relays and possibly a different controller. That said, I designed a circuit that does just that; it's for a repeating cycle tester at my work. I'm using a BS2 OEM board as the controller and a pair of DPDT relays to flip the polarity. It's a simple circuit to make on a small protoboard, and I can supply the code. PM me if you'd like to know more.
Another option is to use a 90° servo motor and controller - there's lots of ways for controlling the servo, and you get the advantage of being able to rotate the head at various speeds.


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## David_AVD (Nov 9, 2012)

I've just made a board for a slightly different purpose, but could probably be used for props like that.

It has a pair of relays arranged to reverse a motor. There are two trigger inputs, as well as two feedback inputs that could be used with limit switches.

I actually wrote some basic code for it yesterday. It's based on a ATtiny20 micro.


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## toozie21 (Aug 23, 2012)

David_AVD said:


> I've just made a board for a slightly different purpose, but could probably be used for props like that.
> 
> It has a pair of relays arranged to reverse a motor. There are two trigger inputs, as well as two feedback inputs that could be used with limit switches.
> 
> I actually wrote some basic code for it yesterday. It's based on a ATtiny20 micro.


That is a nice board David, you selling it anywhere?


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## David_AVD (Nov 9, 2012)

I have a bunch of boards on the go. Some are done and waiting for me to write code and others are still in development.

I do plan on offering them for sale in due course. One of my concerns though is how much postage from Australia to USA will be.


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## toozie21 (Aug 23, 2012)

David_AVD said:


> I have a bunch of boards on the go. Some are done and waiting for me to write code and others are still in development.
> 
> I do plan on offering them for sale in due course. One of my concerns though is how much postage from Australia to USA will be.


Like a true american, I forget that there are people in other countries .

You could always ship large batches to someone stateside and let them ship them for you. I'd be happy to help if it gets some of your awesome products out there (plus you helped me many moons ago with some of my Christmas projects and probably don't even know it, so I owe you).


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## Otaku (Dec 3, 2004)

Just a reminder, folks - let's stay on topic. Thanks...


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## toozie21 (Aug 23, 2012)

Otaku said:


> Just a reminder, folks - let's stay on topic. Thanks...


Mea culpa, a bad habit on the forums and in person...


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## BillyVanpire (Apr 22, 2015)

if your motor can reverse direction when polarity is flipped..
would just a double pole/double throw relay work?

you would need contact switches at the end points in the head swivel to tell the relay to flip.

or am i missing something?


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## David_AVD (Nov 9, 2012)

A DPDT relay to reverse the motor voltage will certainly work, but you'd also need a tiny bit of smarts to make the relay flip state at the ends of the travel.

Since the limit switches will be momentary you can't use them with a single relay to achieve the toggling effect.

EDIT: Actually, you could possibly do it with 3PDT (or 4PDT) relay. I'd have to draw it out.


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## David_AVD (Nov 9, 2012)

I'm 99% sure that this circuit I just drew out will do the trick.

Initially the relay will be off and the motor will be traveling towards the "extended" limit switch. When it hits that switch, the relay will energise (reversing the motor) and the 3rd pole of the relay will latch it on.

When the motor hits the "home" position, that switch will break the relay coil current and the relay will drop out causing the motor to go forward again.

EDIT: This circuit will continuously cycle between the two positions. I just reread the OP and they want to trigger it so is not exactly what is required.


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## David_AVD (Nov 9, 2012)

OK, here's a circuit that uses 2 relays. Shorting the points marked trigger (for 1 sec or so) will start the motor in the forward direction. When it gets to the extended position the motor will reverse. Finally, when the motor returns to the home position it will turn off.


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## Otaku (Dec 3, 2004)

Nice work!
I use two DPDT relays in the circuit I designed and two limit switches that tell the BS2 when to switch the relays on and off. It's a very simple circuit, but it does have the advantage of a bit of logic in the BS2. The microcontroller is there mostly to give me options for the number of cycles I want to run for a given test series. If you (really) trust the repeatability/overrun of your motor, you could do away with limit switches and just use an adjustable oscillating timer to run the relays.


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## David_AVD (Nov 9, 2012)

In my micro controlled version I set a max motor run time (a little longer than it should take) to take action in the case of limit switch or mechanism faults.


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## David_AVD (Nov 9, 2012)

Just had another thought. What about an automotive windscreen wiper motor?

The ones for rear screens have the gearbox mech set up to do an approx 90° sweep and have a set on contacts that open in the home position.

To trigger that you'd just need one SPST relay.


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## Mazz (Jun 24, 2007)

Great ideas, folks. Unfortunately, I don't really know anything about electronic boards etc.


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## BillyVanpire (Apr 22, 2015)

nice work david, i figured there should be a simpler solution to this movement.

@Mazz, using the method david describes all you need is a rear window wiper motor (with its gearing), a simple relay and a power supply.

find an old computer tower and use the power supply to give you 12v (or 5v, etc)
find an auto/electronics store for a single pole/single throw relay.
find an auto wrecker for a rear window wiper motor.

then make it work


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