Halloween Play-Doh Dispenser

As a result of the concerns around trick or treating and COVID-19 I decided to make a treat dispenser for Halloween to allow kids to trick or treat safely, and have a brief moment of normalcy. I saw many people online building way to give out candy while being socially distanced like candy chutes. They were good ideas, but I saw a way to challenge myself and my engineering skills. My concept was to build a machine that would dispense a single treat per child without any physical contact with the device. So I built this, the Pumpkin 3000 as my son likes to call it.

The Play-Doh canisters would sit on a simple incline plane (slide). I use some old 1/8" plywood from a former build, about 1.5'x2.5'. Using a piece of cheap common wood I cut a groove with my table saw in it so that the plywood would fit in. This would be the primary guide for the slide so that Play-Doh containers wouldn't fall out. To hold everything in place I opted for hot glue. (No judgement here this was a last minute build and I have two kids so limited time to work on it. lol)

Just a small note, the stand which you don't see much through this Instructable is reused. It was the back part of a firetruck I made my son to ride in a few years ago for Halloween. https://www.instructables.com/Halloween-Firetruck/

So the Play-Doh canisters slide easily down the plywood, but I needed to control them so they would go one at a time. I designed and 3D printed a simple four spoke cog which had an opening in the center to fit over a small stepper motor. I measured out the correct mounting position and drilled my hole for the motor shaft to come through and connect to the cog. The stepper motor was then hot glued into position. I took a piece of scrap wood and made an assumption that I could use it to make a V feed for the Play-Doh. I also put a piece of plywood over it so the canisters wouldn't pop out when they were pressing against one another. Unfortunately I discovered immediately that when I filled the feed full of Play-Doh canisters, they'd jam up. I discovered this after I glued the plywood top piece on, this is a good reminder to test often. I removed the plywood cover, added a straight piece of cardboard for a simple straight chute for feeding the Play-Doh and then replaced the cover. This reduced my ability to hold what I hoped would be 20 canisters to about 10. I attached a small lever switch so I could detect a quarter turn, because the stepper motor isn't great at turning exactly at the rate and speed I wanted when under load.

Using a 2'x2' piece of plywood from an old project I painted a pumpkin on the front. I 3D printed an L shaped mouth, which could pivot to "open" revealing a Play-Doh. Using a jig saw I cut a hole for the L shaped piece. One side of the 3D printed "mouth" was attached to a servo, the other side was held in place with a pin and bracket that I 3D printed. The bracket and servo were hot glued to the plywood.

For the controller I used an Arduino compatible NodeMCU board. I attached a simple power adaptor which would convert to both 3.3v for the NodeMCU with 5v for the servo and stepper motor. The canisters would sometimes fall too fast or hard, resulting in them falling off of the L shaped mouth piece. I hot glue some cardboard "guides" so that the canisters could only land in the mouth.

I wanted a true contactless approach, so I used the Blynk.io platform rather then a button trigger for the kids to press. This allowed me to create a simple phone app which could connect to the board, via wifi, using an Arduino library. I have attached the code I wrote. When a child approached I pressed the dispense button in my app. This would rotate the cog a quarter of a turn dropping one Play-Doh into the mouth. The mouth would then open for 5 seconds allowing a child to take the Play-Doh. If the mouth closed before the child took it, I had created a second button which would open the mouth for an additional 5 seconds without dispensing additional Play-Doh. This allowed children as many tries as needed to take the Play-Doh in case they were scared or excited.

I posted my progress on a local facebook group to advertise our safe trick or treat option. I was noticed by The Hartford Courant and ended up with an article in the paper. My wife suggested I make some updates just in case we get more kids then we were expecting. I added a small caddy to the right side to hold some hand sanitizer. I also took some small skulls, inserted LEDs for eyes and had a simple 2032 coin battery powering them (side note the eyes are still on over a week later). These were hot glued to a thin 1/4" dowels and stuck into the ground every 6-7 ft as social distancing guild markers.

Here are the links to articles I was mentioned in:
Hartford Courant: https://www.courant.com/news/connecticut/hc-news-connecticut-halloween-treat-dispenser-20201030-pa7cdfrqnjcxblflvmancqa6su-story.html

We-Ha.com: https://we-ha.com/halloween-in-west-hartford-2020-style/

In the end we had a strong turn out with over 70 kids showing up, about double what we normally get. I was please with the numbers as many families decided not to trick or treat this year. I hope you liked this build, I am happy to answer any questions you might have.