Halloween Chocolate Thrower

For Halloween this year I thought it would be an interesting challenge to break out my LEGO Mindstorms EV3 set and build a robot for dispensing candy. These mini chocolate bars are pretty common where I live, so building a machine that would toss them at the kids seemed like a great idea!

It uses the EV3 Infrared sensor to detect when something is in front of the machine to trigger the delivery mechanism. The chocolates are stored in a gravity feed stack and are pushed out from the bottom using a simple piston arm. Once they are pushed out, they land on a platform that is rotated up to throw them.

I designed the feed system to be adjustable, so it can accommodate a range of these mini chocolate bars. Or pretty much anything that will fit and stack reasonably well.

The building instructions and program file for running it are here, and there are some construction notes below, along with the wiring info.

Instructions

Building Guide

PDF File

Digital Model Files

LDraw File

Instructions for wiring the motors and sensor are as follows.

Infrared Sensor: Port 1
Motor under the throwing platform: Port A
Motor under the feeding tower: Port B

This robot performs best with items that are rectangular and stack well. Some mini chocolates which are rounded on the top might not stack so well, so you might get mixed results with them. All the chocolates I showed in the video work quite well.

I had an absolute blast building and playing with this model, and eating all the chocolate that’s been lying around! I hope you have fun with it too.

Chocolate Machine

Jason Strikes Back!

This week marks three years since I built my Ultimate Useless LEGO Machine! In all that time, I still haven’t figured out a way to turn it off. At last I will have my revenge! Or will I?

There is actually some cool programming going on here. The black box and the hand robot coordinate their behaviors using the Mindstorms Bluetooth capabilities. I have to say, I was super impressed with the ease and performance of this feature. Kudos to the EV3 team for such a fantastic implementation!

Despite what it might look like, the black box robot is actually driving the entire sequence. It sends messages to the hand robot to tell it what to do, then it either does an evasive maneuver, or waits for the hand to turn the switch off.

It responds to the switch being turned off the same way it always has, using the light sensor inside. It doesn’t use the proximity sensor to detect when the hand is there though. Since it is telling the hand what to do, it always knows what is going on. The hand would always trigger it anyway, since it is always above the sensor.

Instructions for building the the black box can be found in my original blog post. I haven’t put together instructions for the hand robot. Had a lot of fun making this video, hope you enjoy it!

LuuMa Hand

EV3 Egg Decorator

With Easter just around the corner I thought it would be a great time to dust off my EV3 and build an egg decorating robot. These machines, commonly referred to as Egg Bots, have been around for a while. In fact, an early version dates all the way back to 1990! Since then, many versions have been created, some scratch built and some others using LEGO Mindstorms. I really enjoy the challenge of designing my own models, so here is my version, the EV Egg Bot! Instructions, program file, and notes for building your own can be found below. Other than the eggs and marker, all the pieces you need to build this model come in the EV3 Home Edition kit 31313.

Instructions

Building Guide

PDF File

Digital Model Files

LDraw File

The motors should be connected to the ports as follows:
Port A – the large motor that turns the egg
Port B – the medium motor that raises and lowers the marker
Port C – the large motor that moves the arm from side to side

Operating the EV Egg Bot is pretty straight forward. Once the program is running, you can use the left and right buttons on the EV3 unit to scroll through the available patterns and select the center button to ‘print’ it. Before decorating you’ll want to make sure the marker is about .5 cm/.25 in above the surface of the egg. I’m using standard Sharpie markers, but I think any felt tip marker that can draw on an egg will do.

The video should give you a pretty good idea of how it all works. Feel free to delve into the program file to design your own patterns!

EV Egg Bot

EV3 Cookie Icing Machine

After returning from my trip to Qatar for the Word Robot Olympiad, I was super psyched to build another LEGO Mindstorms machine. Kristal suggested that we build a cookie icing machine for the upcoming holiday season, and so, we present to you, the EV Icer!

EV Icer

I have put together building instructions for the EV Icer, along with the program file for running it, but be sure to read the operation notes below! The icing results can vary drastically depending on many factors. When everything goes according to plan it actually works quite well. All of the cookies in the picture at the end of the post were iced using the machine. To build the EV Icer you only need the LEGO Mindstorms retail set number 31313.

Instructions

Building Guide

PDF File

Digital Model Files

LDraw File

The motors should be connected to the ports as follows:
Port A – the medium motor for the cookie turntable
Port B – the large motor for the squeeze roller
Port C – the large motor that pushes and pulls the turntable assembly

The most important factor to successfully icing a cookie is the consistency of the icing. If it is too runny you will get a blobby mess. If it is too thick you won’t get a complete design. It’s hard to describe the ideal consistency, but it’s probably about the same as you would want if you were icing the cookies by hand. You may have to experiment to find the right balance. Don’t expect it to work perfectly the first time you try it.

You will probably get icing everywhere, especially if it is too runny. Be sure to adjust the height of the ‘ice stopper’ so that it blocks the end of the icing tip when it’s not icing. For smooth operation of the squeeze roller it is best to fold the sides of the icing bag in on itself as you drape it over the squeeze plate, before securing it in the back.

We are using a Wilton brand decorating tip (#4 Round) with a Wilton brand Coupler, which fits snugly in the bracket I have designed (see picture below). I don’t know if other brands of icing tips/couplers are much different, but if they are you will need to improvise to keep the icing tip secure. We are just using a generic icing bag.

The height of the icing tip should be adjusted (by sliding the entire squeeze roller/plate assembly up or down) so that it is just above the top of the cookie.

The patterns are designed to work with cookies that are 9 LEGO studs in diameter. Any larger and the cookie will get caught up in the frame. If they are much smaller the icing will be placed off the edge of the cookie.

Feel free to delve into the program file to adjust some of the variables. Manually adjusting the power applied to the motors is one way to accommodate icing of different consistencies.