by littleBits November 20, 2013
Powered with littleBits, this programmable lazy susan doles out dishes with a mission – to equally distribute food. With two timeouts, the tray spins on a dc motor in timed increments. Set how long the tray waits before it spins as well as how far it turns in between. Try it out at your Thanksgiving table or next party!
Find a disposable serving tray for the top of your lazy susan and a box to use for the base. The box should be big enough to support the plate with its rim. We used 16” plastic plate and a circular tin box with a 7” diameter. Be mindful that if the plate is too big and heavy, the dc motor may not able to turn it.
Build the circuit: power + inverter + double OR + timeout (on-off mode)+ wire + dc motor + wire + led + timeout (off-on mode) + wire (goes back to the other input snap of the double OR bit). The led module was added to indicate when the tray spins. You could add a buzzer to warn the user as well, or you can eliminate them both considering UX aspect of your project.
Set the time on timeout modules to control how far the serving tray will rotate for and how long it will remain stationary in between rotations. The first timeout, which sits directly after the double OR module, decides how long the tray will turn for. The other timeout bit controls how long it stays still. To adjust time, use the small purple screwdriver to turn the small x-shaped dial (trimpot) on the timeout modules. These little dials are VERY sensitive, and range from 0 - 5 minutes, so you will have to play around to get the time timing just right.
Now for the large tray. Make sure the bottom of your tray is clean and flat. Then take sandpaper and roughen up the bottom center a little. This will help to glue parts to this area.
Make a piece with a 3mm D-shaped mounting hole. We used a laser cutter, but if you don’t have access to a laser cutter, you can use a ready-made part with 3mm shaft hole. (for example, http://www.pololu.com/product/1420 ). Glue this part to the bottom of the very center of the tray. You can also use the motorMate and try out some of the motorMate tips & tricks from our blog.
Drill a hole at the very center of the bottom of the circular base container. It should be slightly bigger than the diameter of the motor shaft (3mm).
Make a ring that goes around the rim of the circular container. We made our ring out of acrylic, but other materials will work as well. This ring is supposed to work as a sliding bearing so it is best if you choose a material with a smooth surface. You may even want to add some soap or WD-40 to reduce friction. If you want to be able to put a lot of weight on your spinning tray, you might want to use a lazy susan turntable bearing (http://www.tapplastics.com/product/plastics/acrylic_displays/revolving_display_bases/355)
This step may not be necessary to your process, so you can decide if you need the ring or not.
Grab a block of balsa wood, and cut a channel at the one end of it. The width of the channel should be 0.7 inch and the depth should be 1.0625 inch. This is where the dc motor module will sit.
Measure how deep your container is and cut the balsa block to the same height as this measurement. Have the motor shaft pass through the hole you made in the bottom of the circular container and stick the balsa block to the surface around it. Use adhesive to stick it in place - epoxy works well for this.
Make a hole in the wall of your container for accessing the power switch. Be careful not to cut yourself if you are using a tin box like us.
Place your circuit inside the container. Feel free to use extra wire modules in order to fit the circuit in the container.
Use the top of the container to close up the base at the bottom. The motor shaft should now be sticking out of the top of your enclosed container. Place the large tray on top of the d-shaft, making sure the d-shaped hole from the tray matched up with the d-shaped shaft.
Turn the switch on to be an efficient and fair server!
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