# Servos for props



## tattman98 (Jun 29, 2011)

Looking to go into a new line of props, Have made animated props before.
I have always used wiper motors and oscillating fan motors. Now I want to jump into servos for my props with light sensors, so they move on command. This is a whole new undertaking for me. I thought this year we would give the haunted house a break. Therefore I have another full year to get my props into action. Can anyone help me with this, I have a few ideas on what I would like to do, I have no idea where to start. HELP ME PLEASE........


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## neverhart (Sep 5, 2011)

I'll start you off, but there's a ton of information out there.

Servos usually rotate 180 degrees. You can position them anywhere inside this range with a PWM signal from some sort of controller. The controller can be a simple 555 timer circuit, a microcontroller like a PIC or Arduino, or a wireless controller like those found in RC cars. 

Servos have three connections: Ground, Power, and Signal. Hobby servos are usually rated around 6V. They are electronically "noisy" so usually need a separate power source than the controller (but remember to connect the grounds from the two circuits.)

They're usually best at small, light movements. The wiper motors from your props probably provide much more torque than your standard hobby servo, although you can buy beefier servos... however since they can be positioned they tend to be more expensive than simple motors that are simply on or off. Your local hobby shop will have servos, or you can find them online at sites like servo-city.com to get an idea for prices. I like to buy them in larger lots on auction sites to get the cost down.

If you have specific questions, I'm sure everyone here would be happy to throw down with some answers. Good luck!


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## Lightman (Aug 25, 2014)

Great summary Neverhart. I can add that hobby servos also come in "continuous rotation" mode. The PWM signal corresponds to speed and direction.

There are several cheap servo testers out there to get you going quickly. Tstraub has a cool servo tester with LCD readout to help set positions.


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## tattman98 (Jun 29, 2011)

Ok, thanks Guys I didn't know that hobby shops would have them. What I really need is to know the movements on different models. I have a specific idea in mind for my first (prototype) for the lack of a better word, that is what we shall call it.. What I want is to make a body rise from about the midriff to the height of a normal person. And do it slowly, and to make the mouth and arms move simultaneously. I saw this at a Halloween shop and liked it a lot.. So this will be my first attempt.. Thanks again guys for your help..


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## Mr_Chicken (Nov 26, 2008)

It's not that you can't do that with servos, but I think it's a little complicated for a first project. Off the shelf hobby servos don't generally have the kind of torque you'll need for lifting a whole torso, except at well over $100 each. My advice would be to start with something, like a talking skull, that's a little simpler and well documented so you can learn the basics.


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## neverhart (Sep 5, 2011)

Servo movement is generally all the same: it's a rotary motor. They come with servo "horns"... attachments that act as levers and can help turn the rotary motion into linear (pushing/pulling) motion, but the range of motion is going to be very small. If you think about an RC car's front wheels turning, thats usually the range of motion you're looking at with a hobby servo. To move something over a linear foot, you're either looking at a linear actuator (over $100) or you're back to your motors. I've used stepper motors (the motors that drive 3D printers) as a winch to move things slowly... they're nice because you can tell them to rotate a certain number of turns. If you used a regular motor, you might use a limit switch to turn off the motor once its gone far enough. Since you want the motion to happen slowly, you might look at a screw drive like what's on a garage door opener... in which case a motor is your best bet again to achieve the required torque. 

Now making the mouth move on a prop is a perfect thing to do with a servo, and there are plenty of projects that demonstrate all the details. You could probably start by googling "installing a servo in a bucky skull by scary terry", which takes you through the general idea, then adapt it for your needs. 

And while I never thought this sentence would make sense (-: you should listen to Mr. Chicken. I wanted to jump into the deep end when I started, but it took me a few years to crib together what I needed to know, and it was actually quite fun.

You have lots of parts to your project that all need to be addressed (controller? servo/motor? rising motion? arm motion? talking? speakers? power supply? armature? ) Maybe tackle one piece at a time, breaking it down to something you can achieve for this year, and improvements for next year? 

Here's a thought: usually the store-bought prop's movement is very simple (cheaper) but very clever. Have you peeked "under the robe" so-to-speak? I went to Spirit over the weekend for inspiration and snapped some pics of things I could build better... it's only fair since I'm pretty sure they browse forums like this looking for ideas.


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## tattman98 (Jun 29, 2011)

You are correct about that neverhart. I have made props and it seems the very next year they have them...Thank you for information in any case it will be used wisely....


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