Hi everyone. This is a great site, lots of excellent info. I am new to anamatronics and was stoked to find this forum.
I am going to a crazy hat party and want to animate a Steampunk hat. I want to have the lid of the hat lift up and a puppet come up with it and say a joke, and some LED lighting. I have gone thru almost all of the posts on the forum and I have found most of the info I need but I will still need some help putting it all together. I am hoping I can get that here. I have not done any programming but found n great step by step tutorial here: www.instructables.com/id/Arduino-animatronics-make-your-awesome-costumes-m/
If someone has any suggestion or other ideas please let me know.
To keep it simple I think that only the front part of the lid should lift, with the back part acting as a hinge. I will need about 3" of lift. Because I will be wearing the hat weight is important. Any suggestions on how to accomplish 3" of lift. Most of the micro/mini servos do not have a horn with that much movement. I have seen some mini actuators but they would be too heavy. If I have to use a lever mechanism, how do I determine the needed torque.
I am starting building the hat today. Here is a Pic of the hat I am going to make.
I want to have the keyhole back lit with a LED.
Thanks in advance for this great form and the help.
Post by propmaster2000 on Jan 16, 2017 14:19:57 GMT
Wow, this is a very ambitious project. Not only are you creating the hat from scratch, but you are building the Arduino Controller and servo circuit as well. Can't wait to see your progress. Take lots of pictures to document your steps.
Sounds like a cool project. Much of what you can do will depend on how much room you have in the hat. There are lots of different ways you can do this. If you can fit at least a standard size servo you can put a longer output arm that would allow for the 3" lift. You could have the long arm move a rod that lifts your puppet. That's probably the simplest solution. You could also use a multi turn servo like this one with a vertical gear drive- www.servocity.com/hs-785hb-servo
Using a multi turn servo with a servo drive gear (https://www.servocity.com/32p-24t-c1-spline-servo-mount-gears) and a gear rack (https://www.servocity.com/32-pitch-standard-gear-rack) will allow you to get the necessary vertical lift. You will probably need to mount the gear rack to a small linear slide. A slide like this one from Igus would get the job done- www.igus.com/wpck/3594/drylin_n_NK_02_17
Basically you have to figure out the weight of the hat lid and puppet and from there you can figure out the right servo drive gear to use. That servo is pretty powerful and since it will turn four rotations you could use a relatively small drive gear. Remember that the servo torque rating is with a one inch output arm (which equates to a 2" diameter drive gear. By using a smaller drive gear you will increase the torque rating.
What I would do is figure out the smallest gear that will give you just over 3" of movement, given the servo's four rotations. Since circumference = 2 (3.14) x radius, a 1" pitch diameter gear (32 tooth) should give you enough movement, just over 3". The torque rating of the servo is then doubled to 366 oz/in @ 6V power (using 4 AA alkaline batteries.) That of course is the stall torque (the point at which the servo will stop moving) so in reality I'd probably go 1/2 that value to play it safe. That means that your puppet and hat lid should weigh around 183 oz (which is silly heavy!)
Now you have to figure out speed. Most servos are rated in terms of how fast they can rotate the output shaft to 60 degrees. Using the specs for that servo, it would take 5.6 seconds for it to turn the gear four rotations and lift the hat lid- and that's if that hat lid were really light and there wasn't a puppet. That's really slow and I'm guessing you want it to move a lot quicker- sort of pop up out of the hat. So this is where the gearing and weight of your puppet comes into play. Once you figure out the weight of your puppet you can work backwards to find the right gear size that will give you enough movement with decent speed. If you puppet is light weight you could even use a standard servo with a larger gear to get the necessary movement/speed.
As an example, if you could get your puppet/lid weight down to around 8oz (.5 lb) you could use a servo like the Hitec 5585MH (https://www.servocity.com/hs-5585mh-servo), which has a torque rating of 236 oz/in @ 7.4 V so with a 2" diameter gear it could lift your puppet 3" in probably a little over one second. It's a lot faster because of the larger drive gear and the fact that the servo only has to rotate 180 degrees to get 3" of lift. If you go with a simple arm/rod solution to lift the puppet remember that that you will be reducing the servo output power: servo torque is rated using a 1" long output arm, so a servo that outputs 236 oz/in will output half that amount with a 2" long output arm. Using this info it becomes apparent very quickly that the lighter weight your puppet the smaller/less powerful/less expensive servo you can use!
For a controller I'd use the 3.3V Arduino Pro Mini or an Adafruit Pro Trinket. Both are small and cheap and will get the job done. Take servo power directly from the battery pack and use a regulator to step down the pack voltage for the Arduino. Adafruit also has a small sound board that would work and you can wire the LED back light directly to an output pin.
Post by propmaster2000 on Jan 17, 2017 14:24:09 GMT
Hi hobib, Another option to consider:
I have used both servo and plan geared motor drives. Many times I have used low voltage DC motors that have gear driven shafts. They have a fair amount of torque and speed. The thing you need to know is that since there is no feedback to stop the motor, you will need end travel DPST micro switches (N.O. / N.C. contacts) to stop the motor at the top and bottom of the puppets motion.
Since the motors are DC, you can reverse the polarity to change it's direction. When the puppet reaches the top of it's 3" travel, the upper micro-switch will open removing voltage. When you reverse the polarity, a DIODE will allow the motor to see this voltage and start down to the bottom until it hits the lower switch and diode and stops. Then the process starts over.
To reverse polarity, you can use a simple circuit with a DPDT relay wired as an X. Normally open and closed contacts of the relay are the key.
The positive and negative DC will go into the two poles wired as an X, then out the common of each relays contacts. When you energize the relay coil with a switch, the polarity is allowed to change at the commons and to the motor. The motor speed is set by it's voltage.
As a motion slide for the puppet, you could use two brass tubes (one outside the other like a piston). nested together to create this slide action. The inner tube would be mounted securely at the bottom, while the outer tube is allowed to slide up and down freely. Micro switches would be located at the top and bottom of it's travel. The brass tubes would be large enough to give the puppet good, secure movement. The outer tube would be attached to the inside of the puppet. Also, I have found that PVC pipe is another good inexpensive option. One tube inside another could be used to support the puppet and move up and down with a slot in one tube and a pin in the other. You can then use a cable and pulley setup attached to the motor shaft to move the outer tube up and down. There is no clutch on gear driven motors, so the shaft will turn where it wants. If you design a rubber wheel setup, that might give you some "slip" if it jams up.
I think if the lid of the hat is made light enough, the puppet would just push the lid open when it comes up and falls when it goes back to home position. Your sound circuit could be wired to the control relay as well.
Please note: This information should be used as reference only. You should have a good understanding of electronics before attempting. . . .
Post by propmaster2000 on Jan 20, 2017 18:29:47 GMT
Hi again Hobib,
Since my last post, I wanted to mock up a prototype of my design explanation above. I decided to go the PVC route instead of brass tube. Since the mock up started to get a bit larger then I anticipated. There are two sizes of PVC, 1 MODIFIED servo motor, two pulleys and cable, 2 micro limit switches and small relay to change the polarity to the drive motor. The motor started out as a non-continuous rotation servo drive. Since the gear ratio was good for the torque I need, I removed all the electronic feedback and control circuits. Also, the mechanical stop pin was taken out to allow the motor to rotate 360.
Here is a video of the mock-up hat and Sock puppet: