Since this is the first project I have placed on Element 14 I will introduce myself. I am a retired mechanical engineer who got into electronics when my grandson asked me to build him an airplane several years ago and we put some “avionics” into it. Of course it turned out looking like something I would have liked to have had myself back in the '50s .
Since that time I have attracted more "customers" and have steadily increased the complexity. I use MSP430 microcontrollers, WS2812 LEDs, scrap electronics, cardboard, things from the Dollar Store and whatever I have on hand for these builds. This year my granddaughter wants to be “Ladybug Girl” with flapping wings and a tiara. My grandson wants to be “Rocket Boy”.
Microcontroller
I designed a custom PCB for the Texas Instruments MSP430G2553 microcontroller that I use for wearables.
It can be powered by a CR2032 coin cell battery on the back as shown here or by external power. The pins numbers on the front match up with the Texas Instruments MSP430G LaunchPad header numbering with actual port designations on the back. The four pads on the front top with 0.1” pitch are for programming as will be explained below. I use 0805 SMD parts which I find easy to solder by hand. On this latest version I have placed a WS2812 (aka “neopixel”) and there is a red LED and a button for the user. The pads on front right are used for stringing additional WS2812 LEDs and an IR sensor. Here is the schematic.
Ladybug Girl’s Wings
I started with wings I found at the Dollar Store. Movement is from a servo, power from a battery pack with 4 AAA cells and control by the custom MSP430G2553 designed for these creations.
I attached the wings to a small piece of wood and built a cardboard enclosure for it. The enclosure is covered in black fabric and held shut with Velcro. The servo pokes through to the front and moves the wings up and down by pulling with monofilament fishing line. Hot glue, a bit of stitching and elastic hold everything together.
The MSP430 cannot handle 6 volts so there is a LD1117AV33 LDO voltage regulator to bring it down to 3.3 volts. And that is all there is to the electronics.
Since the MSP430G2553 can be programmed using Energia, a fork of Arduino, I just used the servo library and modified the speed and limits of the servo to meet my needs. The final product is shown in the short clip below.
Ladybug Girl and Bumble Bee’s Tiaras
Lady Bug Girl has a baby sister that will be a Bumble Bee this year. Last year I made a tiara for Ladybug Girl and that was a hit so I thought it would be nice to make one for both her and baby sister that synchronize and can be controlled wirelessly. After looking at the power requirements and the limitations of a CR2032 battery I selected infrared. By using sleep modes on the MSP430 and reducing the brightness and number of WS2812 LEDs lit at any one time it is possible to get down to 4 mA or less current draw and get acceptable battery life. The plastic tiaras came from the Dollar Store again. The infrared receiver is hidden behind the top LED.
I made a PCB for the WS2812s that are embedded in the tiara so that they can be tested as a string and then individual LEDs snapped off and used as desired. The 5050 WS2812s are a bit fiddly to solder up by hand but otherwise no worries.
The tiara schematic is below. Note that the TSOP38238 IR receiver fits nicely into the 3 through-hole pads provided on the MSP430 PCB and the WS2812s are in series with the one onboard.
Infrared Controller
For the infrared controller I am using a prototyping PCB that I designed to fit in an off the shelf project box.
The microcontroller is a MSP430G2553 again with a LED, two user buttons, on/off power switch, headers that match the standard Texas Instrument BoosterPack headers, and a prototyping area. The optional display is a Nokia 5110 and there is provision for an external XTAL . I hand cut the opening for the Nokia display as well as the openings in the end plate. The photo below shows the open enclosure with the prototyping PCB adapted for use as an IR transmitter. The IR LEDs, power switch, and control buttons are in the end plate at top.
The IR transmitter is driven by a NPN Darlington transistor and while 10 LEDs are shown in the schematic there are only 5 in this build.
IR transmission is done by bit banging modulated serial over the IR LEDs at 2400 baud.
A TSOP38238 IR receiver and UART do all the work on the receiving end and the TSOP38238 converts the modulated IR directly into serial that the UART can handle. I haven’t seen this done before (although I am sure someone else has done it) but it works reasonably well. I use a SPI hack to control the WS2812 LEDs.
Programming
A MSP430 LaunchPad (in this case a MSP430G5529) is used to load the firmware with pogo pins attached to jumpers that are pressed firmly against the PCB with the microcontroller to be programmed. This works well if not too many microcontrollers are being programmed.
The programming leads were made by pushing the pogo pins through a 4x DuPont female header, soldering leads to the pogo pins and then tying everything together with heat shrink insulator.
The clip below shows a finished tiara being tested with the IR Transmitter.
Rocket Boy
Rocket Boy is always quite specific about what he wants. The rocket backpack was to have a motor, lots of LEDs, and have hand held control. The build consists of two coffee cans for fuel canisters on the sides with cardboard and foamboard to hold it together and form the rocket enclosure. I placed a latching pushbutton into a cylindrical USB device that never worked to switch it on and off. Webbing is used for the adjustable straps. A MSP430 controller is placed where it can be seen in the middle of the backpack (this is an old version that uses standard SMD LEDs instead of WS2812s).
There is a small cooling fan underneath the “grill” with a WS2812 ring around it. There is a half circle pasted on the fan for visual effect. The batteries and supporting electronics are hidden in the structure. Some of the parts, such as the switches, battery holder, and WS2812 ring are off of the original airplane costume. The cardboard is covered in metallic paper for aesthetic purposes and the MSP430 sits inside the plastic lid from one of the coffee cans. The tops of the two fuel canisters are from a Styrofoam ball cut in half and painted silver.
The motor is controlled with a NPN transistor and has a flyback diode as seen in the schematic below.
The firmware is equally simple. The motor is either on or off (no PWM) and the WS2812s are controlled with the SPI hack.
For the most part these are revisions and upgrades to previous Halloween projects I have done over the last three years. I enjoy making them and the kids have fun with it too. Adults always comment and seem to appreciate the handmade aspects as well as the recycled parts. Last years Fairy Princess and Jet Pilot are below. Thanks for reading…
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