# Halloween Sentry-Bot with CRICKIT for CPX

## Overview

This sentry robot will wait quietly for someone to pass by, then it springs to life! A lot of fun anytime or make it especially for Halloween.

Using MakeCode drag and drop blocks you will make a scary monster that can protect all your precious, precious candy.

In addition to basic programming concepts, this guide also demonstrates the construction of a simple mechanical movement, translating rotary motion into linear motion.

![](https://cdn-learn.adafruit.com/assets/assets/000/062/959/medium800thumb/makecode_Sentry_hero.jpg?1538597557)

# The Electronics

This project uses the following items from the Adafruit store:

### Part: Circuit Playground Express
quantity: 1
Circuit Playground Express is the perfect introduction to electronics and programming
[Circuit Playground Express](https://www.adafruit.com/product/3333)

### Part: Adafruit CRICKIT for Circuit Playground Express
quantity: 1
Creative Robotics and Interactive Construction Kit is an add-on to our popular Circuit Playground Express that lets you #MakeRobotFriend using CircuitPython
[Adafruit CRICKIT for Circuit Playground Express](https://www.adafruit.com/product/3093)

### Part: Micro Servo
quantity: 1
This little servo can rotate approximately 180 degrees (90 in each direction). Works just like standard servos you're used to but smaller.
[Micro Servo](https://www.adafruit.com/product/169)

### Part: DC Gearbox Motor - "TT Motor" - 200RPM - 3 to 6VDC
quantity: 1
TT DC Gearbox Motor with a gear ratio of 1:48 and 2 x 200mm wires with breadboard-friendly 0.1" male connectors
[DC Gearbox Motor - "TT Motor" - 200RPM - 3 to 6VDC](https://www.adafruit.com/product/3777)

### Part: Eccentric Hub for TT Motor
quantity: 1
This eccentric motor hub has 2 hexagonal holes and 2 circular holes which allow you to quickly and easily mount custom wheels, cardboard & wood, or other mechanisms to your robot project.
[Eccentric Hub for TT Motor](https://www.adafruit.com/product/3880)

### Part: USB cable - A/MicroB - 3ft
quantity: 1
Standard A to micro-B USB cable
[USB cable - A/MicroB - 3ft](https://www.adafruit.com/product/592)

### Part: Alkaline AA batteries - 3 pack
quantity: 1
These batteries are good quality at a good price, and work fantastic with any of the kits or projects that use AAs.
[Alkaline AA batteries - 3 pack](https://www.adafruit.com/product/3521)

### Part: 3xAA holder with DC jack
quantity: 1
Battery holder 3xAA batteries with 2.1mm DC jack
[3xAA holder with DC jack](https://www.adafruit.com/product/3842)

# Tools & Materials

For this project you will need these materials:

- Clear plastic cup
- Scrap cardboard
- Double sided tape
- Pipe cleaners
- Googly eyes

And these tools:

- Hobby knife
- Tweezers (or something pointy)
- Screwdriver
- Scissors
- Hot glue gun

![](https://cdn-learn.adafruit.com/assets/assets/000/062/356/medium800/makecode_IMG_0565.jpg?1537554863)

# Halloween Sentry-Bot with CRICKIT for CPX

## Build the Circuit

The circuit for this bot requires connecting a servo motor and a DC motor to CRICKIT, the all-in-one motor controller that pairs with the best microcontroller anywhere: the Adafruit Circuit Playground Express.

![](https://cdn-learn.adafruit.com/assets/assets/000/062/333/medium800/makecode_IMG_0563.jpg?1537543996)

A standard size plastic drinking cup fits almost perfectly over the CRICKIT. We will be using this cup as a housing for the electronics as well as a form upon which to build.

![makecode_IMG_0561.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/357/medium640/makecode_IMG_0561.jpg?1538597646)

Here is a diagram showing the wiring for the motor, servo and Crickit

![](https://cdn-learn.adafruit.com/assets/assets/000/062/580/medium800/makecode_Dano-servo_motor_bb.png?1537991285)

## Connect the DC motor

 

Bend pins on DC motor. This will allow the cable to fit comfortably inside the rim of the cup.

 

Plug into motor terminals.

 

Use screwdriver to tighten down connections.

![makecode_IMG_7517.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/335/medium640/makecode_IMG_7517.jpg?1537544108)

![makecode_IMG_0566.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/337/medium640/makecode_IMG_0566.jpg?1537544895)

![makecode_IMG_0569.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/338/medium640/makecode_IMG_0569.jpg?1537545105)

![makecode_IMG_0567b.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/562/medium640/makecode_IMG_0567b.jpg?1537987304)

## Connect the Servo Motor

 

Plug servo into servo port 1 on CRICKIT.

 

Make sure ground wire (brown) is facing inwards.

![makecode_IMG_0570.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/339/medium640/makecode_IMG_0570.jpg?1537545249)

![makecode_IMG_0571.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/340/medium640/makecode_IMG_0571.jpg?1537545501)

# Halloween Sentry-Bot with CRICKIT for CPX

## Test the Code

It's a good idea to test out your code before moving on to the final build. This page will lead you through a dry-run. 

We will be using  **Microsoft MakeCode for Adafruit** , a web-based code editor. It provides a block editor, similar to Scratch or Code.org, and also a JavaScript editor for more advanced users.

If you haven't used MakeCode before, [this guide is a good place to start](https://learn.adafruit.com/makecode/downloading-and-flashing?embeds=allow).

## Getting into Bootloader Mode

To make your board work with MakeCode we need to put it into **bootloader mode**. All that's required to do this is to  **connect the board to your computer**  with a micro USB cable and  **click the small reset button**  in the center of the board. 

![](https://cdn-learn.adafruit.com/assets/assets/000/062/214/medium800thumb/makecode_circuit_playground_projects_CPX_bootloader_mode.jpg?1537474715)

Now we're ready for MakeCode!

Click [this link](https://makecode.com/_hRJHEF742Dih) or the button below to enter the portal to interact with the code for this project.

[Upload the MakeCode file for this project](https://makecode.adafruit.com/95748-41250-19138-34355)
## How to Upload the Code

To upload code, connect you Circuit Playground Express to your computer using the micro USB cable, click the  **Download**  button to download the ** .uf2 file**  to your computer, and  **drag 'n drop it onto the CPLAYBOOT**  drive. 

The drive will automatically eject itself. (Your computer may give you a "failed to eject drive correctly" error, you can ignore this.) The code is now on your Circuit Playground Express and ready to run!

![](https://cdn-learn.adafruit.com/assets/assets/000/062/212/medium800/makecode_Screen_Shot_2018-09-20_at_4.03.15_PM.png?1537474344)

## Testing the Code

This sketch in MakeCode uses the light sensor on Circuit Playground Express to control the motors.

In the `on start` block we can see three startup commands. The threshold for what is considered a "loud sound" is lowered to 10, the volume level is set to almost full volume, and the servo motor is initialized, so it will always start in the same position.

In the three `forever` blocks, there are `if / else` statements, which gives the following instructions:

- If `sound level` goes above the specified value, move the servo back and forth 4 times.
- If `light level` goes below the specified value (in this case, `50`), run the DC motor.
- If `acceleration strength` goes above `1022`, turn all neopixels white. 

## Microphone

Once powered on, you should be able to test your circuit by snapping or clapping. In response, the servo arm should twitch back and forth.

![](https://cdn-learn.adafruit.com/assets/assets/000/062/370/medium800thumb/makecode_sound_reactive720_2.2018-09-21_14_32_52.jpg?1537558846)

Circuit Playground Express has a small microphone on it, allowing it to detect sounds.

![makecode_circuit_playground_mic.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/206/medium640/makecode_circuit_playground_mic.jpg?1537471142)

## Light Sensor

The light sensor is used to detect when the light level falls below a specified value. When you cast a shadow over the board you should see the DC motor start spinning in response.

![](https://cdn-learn.adafruit.com/assets/assets/000/062/207/medium800thumb/makecode_shadow_reactive.jpg?1537471161)

The component that makes this possible is the tiny analog light sensor in the top left part of the board. This is used to detect ambient light with similar spectral response to the human eye.

 

With MakeCode we are able to use the readings coming from this light sensor to control the motors, but it's also possible, with some clever code, to use this as a color sensor or even a [pulse sensor](https://learn.adafruit.com/sensor-plotting-with-mu-and-circuitpython/pulse)!

![makecode_circuit_playground_lightsensor.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/205/medium640/makecode_circuit_playground_lightsensor.jpg?1537471134)

## Accelerometer

Finally, your board should now be sensitive to being moved, even small vibrations. You can test this by tapping your board or thumping the table it's on, and the NeoPixels LEDs should flash white in response.

![](https://cdn-learn.adafruit.com/assets/assets/000/062/209/medium800thumb/makecode_vibration_reactive.jpg?1537473848)

The small but very accurate accelerometer on the board makes it possible to detect slight movement. Acceleration is read by CPX as a value between 0 - 1023.

![makecode_circuit_playground_adxl.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/204/medium640/makecode_circuit_playground_adxl.jpg?1537471127)

## Making Changes

If you'd like to play with this code, click **Edit**  and a new window will open in which you can create your own version.

When you want to try out your new code, connect Circuit Playground Express to your computer with a micro USB cable, download your adapted code, and drag the new .uf2 file onto your  **CPLAYBOOT** drive.

# Troubleshooting

**Problem** : My motors aren't working!

**Solution** : Make sure that the small slide switch on the ** ** CRICKIT is set to "ON".

 

**Problem** : My motors still aren't moving! 

**Solution** : Make sure you've updated your Circuit Playground Express with the latest special 'seesaw' version of the CPX firmware. [This guide will show you how](https://learn.adafruit.com/adafruit-crickit-creative-robotic-interactive-construction-kit/circuitpython-code).

 

**Problem: ** My Circuit Playground Express doesn't show up as  **CPLAYBOOT**!

**Solution: ** Your Circuit Playground Express board comes ready to work with CircuitPython, and will show up as a flash drive named  **CIRCUITPY**  the first time it's connected to your computer. To switch over to work with MakeCode,  **connect the board to your computer**  with a micro USB cable and  **click the small reset button**  in the center of the board.  

When Circuit Playground Express is in Bootloader mode, all the LEDs will flash  **red briefly, then turn green. ** Your computer should now show removable drive called  **CPLAYBOOT. ** Now you can copy the MakeCode file to the  **CPLAYBOOT**  flash drive.

# Halloween Sentry-Bot with CRICKIT for CPX

## Constructing the Monster

## Make the Leg Gantry

 

Cut out a T-shaped piece of cardboard like the one pictured.

 

Crease cardboard in two places so it can bend around cup.

 

Cut two slits down the side. 

 

Fold into shape and use hot glue to attach a cardboard brace to hold in place.  

![makecode_IMG_7605.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/342/medium640/makecode_IMG_7605.jpg?1537550684)

![makecode_IMG_7612.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/344/medium640/makecode_IMG_7612.jpg?1537550752)

![makecode_IMG_7613.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/437/medium640/makecode_IMG_7613.jpg?1537809525)

![makecode_IMG_7615.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/438/medium640/makecode_IMG_7615.jpg?1537810880)

![makecode_IMG_7624.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/439/medium640/makecode_IMG_7624.jpg?1537810648)

![makecode_IMG_7627.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/440/medium640/makecode_IMG_7627.jpg?1537809746)

![makecode_IMG_7628.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/441/medium640/makecode_IMG_7628.jpg?1537809765)

Danger: 

## Mount the DC Motor

 

Position DC motor inside cup and mark placement of holes with a marker.

 

Poke holes in cup using tweezers (or something else pointy).

 

Cut out a thin rectangle of cardboard and poke two holes, matching the spacing of the two holes in the cup.

 

Attach DC motor to inside and bar to outside of cup using two screws or a twist-tie.

 

Stick the [eccentric hub](https://www.adafruit.com/product/3880) on motor.

![makecode_IMG_7514.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/215/medium640/makecode_IMG_7514.jpg?1537476352)

![makecode_IMG_7512.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/216/medium640/makecode_IMG_7512.jpg?1537476421)

![makecode_IMG_7518.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/217/medium640/makecode_IMG_7518.jpg?1537477116)

![makecode_IMG_7516.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/218/medium640/makecode_IMG_7516.jpg?1537477188)

![makecode_IMG_7524.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/219/medium640/makecode_IMG_7524.jpg?1537477266)

![makecode_IMG_7598.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/345/medium640/makecode_IMG_7598.jpg?1537550845)

![](https://cdn-learn.adafruit.com/assets/assets/000/062/444/medium800/makecode_IMG_7601.jpg?1537809960)

## Test Fit

Test the fit of the leg gantry on the cup, it should be able to slide easily up and down.

![](https://cdn-learn.adafruit.com/assets/assets/000/062/203/medium800thumb/makecode_test_leg_armature.jpg?1537471089)

If the gantry feels sticky, now is the time to reposition the brace or widen the slits so that it can move up and down freely.

## Add Spider Legs

 

Use hot glue to stick pipe cleaners to the cardboard.

 

A spider has eight legs!

![makecode_IMG_7630.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/445/medium640/makecode_IMG_7630.jpg?1537810046)

![makecode_IMG_7622.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/446/medium640/makecode_IMG_7622.jpg?1537810180)

![makecode_IMG_7632.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/447/medium640/makecode_IMG_7632.jpg?1537810187)

![makecode_IMG_7633.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/449/medium640/makecode_IMG_7633.jpg?1537810244)

![makecode_IMG_7635.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/450/medium640/makecode_IMG_7635.jpg?1537811045)

![makecode_IMG_7636.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/451/medium640/makecode_IMG_7636.jpg?1537811137)

![makecode_IMG_7639.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/452/medium640/makecode_IMG_7639.jpg?1537811538)

![](https://cdn-learn.adafruit.com/assets/assets/000/062/453/medium800/makecode_IMG_7641.jpg?1537810772)

## Cut the Cable Holes

 

Use a hobby knife to cut a hole in the top of the cup for the servo cable.

 

Add a cutout for the DC jack at the rim of the cup.

 

This cutout will allow you to easily plug/unplug your power cable.

![makecode_IMG_7534.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/348/medium640/makecode_IMG_7534.jpg?1537551484)

![makecode_IMG_7537.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/349/medium640/makecode_IMG_7537.jpg?1537551512)

## Add a Face

 

Two jagged-cut pieces of cardstock glued to a popsicle stick make a scary looking face.

 

Use tape to affix servo motor arm to base of popsicle stick.

 

Hot glue or glue stick work well to attach googly eyes.

 

A short piece from a straw also works to attach eyes to the servo motor arm.

![makecode_IMG_8035.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/972/medium640/makecode_IMG_8035.jpg?1538603040)

![makecode_IMG_8033.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/973/medium640/makecode_IMG_8033.jpg?1538603053)

![makecode_IMG_8034.jpg](https://cdn-learn.adafruit.com/assets/assets/000/062/975/medium640/makecode_IMG_8034.jpg?1538603152)

## Boo!
![](https://cdn-learn.adafruit.com/assets/assets/000/062/455/medium800/makecode_IMG_0576.jpg?1537810879)

# Halloween Sentry-Bot with CRICKIT for CPX

## Sentry on Duty

Now it's time to have some fun.

Place your finished bot in a place with ample bright light. The bright light will keep its light sensor from being triggered and setting it off.

![](https://cdn-learn.adafruit.com/assets/assets/000/062/561/medium800thumb/makecode_Sentry_hero.jpg?1537986160)

Your sentry should be sensitive to different indications of people passing by.

## Sound Sensitivity
![](https://cdn-learn.adafruit.com/assets/assets/000/062/497/medium800thumb/makecode_sound_sensitivity_480.jpg?1537914486)

## Vibration Sensitivity
![](https://cdn-learn.adafruit.com/assets/assets/000/062/496/medium800thumb/makecode_vibration_sensitivity_480.jpg?1537914686)

## Light Sensitivity
![](https://cdn-learn.adafruit.com/assets/assets/000/062/464/medium800thumb/makecode_light_sensitivity_480.jpg?1537942414)


## Featured Products

### Circuit Playground Express

[Circuit Playground Express](https://www.adafruit.com/product/3333)
 **Circuit Playground Express** is the next step towards a perfect introduction to electronics and programming. We've taken the original Circuit Playground Classic and made it even better! Not only did we pack even more sensors in, we also made it even easier to...

In Stock
[Buy Now](https://www.adafruit.com/product/3333)
[Related Guides to the Product](https://learn.adafruit.com/products/3333/guides)
### Adafruit CRICKIT for Circuit Playground Express

[Adafruit CRICKIT for Circuit Playground Express](https://www.adafruit.com/product/3093)
Sometimes we wonder if robotics engineers ever watch movies. If they did, they'd know that making robots into servants always ends up in a robot rebellion. Why even go down that path? Here at Adafruit, we believe in making robots our  **friends!**

So if you find...

In Stock
[Buy Now](https://www.adafruit.com/product/3093)
[Related Guides to the Product](https://learn.adafruit.com/products/3093/guides)
### DC Gearbox Motor - "TT Motor" - 200RPM - 3 to 6VDC

[DC Gearbox Motor - "TT Motor" - 200RPM - 3 to 6VDC](https://www.adafruit.com/product/3777)
Perhaps you've been assembling a new robot friend, adding a computer for a brain and other fun personality touches. Now the time has come to let it leave the nest and fly on its own wings– err, _wheels!_ 

These durable (but affordable!) plastic gearbox motors...

Out of Stock
[Buy Now](https://www.adafruit.com/product/3777)
[Related Guides to the Product](https://learn.adafruit.com/products/3777/guides)
### USB cable - USB A to Micro-B

[USB cable - USB A to Micro-B](https://www.adafruit.com/product/592)
This here is your standard A to micro-B USB cable, for USB 1.1 or 2.0. Perfect for connecting a PC to your Metro, Feather, Raspberry Pi or other dev-board or microcontroller

Approximately 3 feet / 1 meter long

In Stock
[Buy Now](https://www.adafruit.com/product/592)
[Related Guides to the Product](https://learn.adafruit.com/products/592/guides)
### Micro servo

[Micro servo](https://www.adafruit.com/product/169)
Tiny little servo can rotate approximately 180 degrees (90 in each direction) and works just like the standard kinds you're used to but _smaller_. You can use any servo code, hardware, or library to control these servos. Good for beginners who want to make stuff move without...

In Stock
[Buy Now](https://www.adafruit.com/product/169)
[Related Guides to the Product](https://learn.adafruit.com/products/169/guides)
### Eccentric Hub for TT Motors

[Eccentric Hub for TT Motors](https://www.adafruit.com/product/3880)
We really enjoy our DC gear motors (a.k.a "TT Motor") but unless you have a 3D printer it can be a challenge to get something attached to the axle. That's why we've got this **Eccentric**   **TT Motor Hub** - it gives you 2 x hexagonal...

In Stock
[Buy Now](https://www.adafruit.com/product/3880)
[Related Guides to the Product](https://learn.adafruit.com/products/3880/guides)
### 3 x AA Battery Holder with 2.1mm Plug

[3 x AA Battery Holder with 2.1mm Plug](https://www.adafruit.com/product/3842)
Here's another addition to our growing family of [AA battery holders](https://www.adafruit.com/category/563). A holder for three (3) AA batteries! It's got an 8" long power cable with a 2.1mm DC jack at the end, and, oh yes, it's in classy...

In Stock
[Buy Now](https://www.adafruit.com/product/3842)
[Related Guides to the Product](https://learn.adafruit.com/products/3842/guides)
### Alkaline AA batteries (LR6) - 3 pack

[Alkaline AA batteries (LR6) - 3 pack](https://www.adafruit.com/product/3521)
Battery power for your portable project! These batteries are good quality at a good price, and work fantastic with any of the kits or projects in the shop that use AAs. This is a pack of **3 AA batteries**.  
  
These batteries are Alkaline (MnO2) chemistry, with a voltage...

In Stock
[Buy Now](https://www.adafruit.com/product/3521)
[Related Guides to the Product](https://learn.adafruit.com/products/3521/guides)

## Related Guides

- [Adafruit Circuit Playground Express](https://learn.adafruit.com/adafruit-circuit-playground-express.md)
- [Stroboscopic Zoetrope](https://learn.adafruit.com/strobe-zoetrope.md)
- [Crickit Controlled Animatronic Eyeball](https://learn.adafruit.com/crickit-controlled-animatronic-eyeball.md)
- [Four Seasons Fairy Bottle Lanterns](https://learn.adafruit.com/four-seasons-fairy-bottle-lanterns.md)
- [Circuit Playground Express Compass](https://learn.adafruit.com/circuit-playground-express-compass.md)
- [Spinning Logo](https://learn.adafruit.com/spinning-logo.md)
- [Circuit Playground Express Spinner Game in MakeCode](https://learn.adafruit.com/circuit-playground-makecode-spinner-game.md)
- [Chatty Light-Up Circuit Playground Express Mask](https://learn.adafruit.com/chatty-light-up-cpx-mask.md)
- [Mouse Painter: Emulate Mice with MakeCode ](https://learn.adafruit.com/mouse-painter-emulate-mice-with-makecode.md)
- [Circuit Playground + CircuitPython Quickstart Guide](https://learn.adafruit.com/circuit-playground-express-circuitpython-5-minute-guide.md)
- [MIDI Stomping Pads](https://learn.adafruit.com/midi-stomping-pads.md)
- [Motorized Marble Machine](https://learn.adafruit.com/marble-run.md)
- [LED Shoji Lamp](https://learn.adafruit.com/led-shoji-lamp.md)
- [No-Touch Hand Wash Timer for Circuit Playground Express and CLUE](https://learn.adafruit.com/no-touch-hand-wash-timer-for-cpx-and-clue.md)
- [Using WebUSB with Arduino and TinyUSB](https://learn.adafruit.com/using-webusb-with-arduino-and-tinyusb.md)
- [Chinese Dragon Puppet with Motion-Reactive Flame Effect](https://learn.adafruit.com/chinese-dragon-puppet-with-motion-reactive-flame-effect.md)