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Personalized Message Displaying Trinkets

Around last month, we were welcoming our new freshmen to the department. My friend came up with an idea that we should have some kind of gifts for them, and this is my take for that. It took me a day to experiment on how to build the first one, then several hours to build the rest 4.

The trinket is ATTINY414-controlled. The message is stored on the MCU and then displayed one letter at a time on the common anode 7 segments display. You could have a very long message since my 10 letters word used up only 400 bytes of program space on the 4k device. The 7 segments display cathode pins are connected to the MCU through 1k resistors.

I tried to use as many parts I already have on hand as possible and it turns out we only have to buy battery holders and batteries. The trinket is pretty cheap to build too, coming at just over 2$ each excluding the battery.

This piece is ideal for decoration or for hanging on your bag.

Note: This is my first Instructable and I took waaay fewer pictures than I should. I will make up for those by drawing some sketches for those steps I have no pictures. Also sorry for potentially confusing writing.

Note 2: You can use any microcontroller for this project, butthe placement in this Instructable is for ATTINY414 and other pin-compatible devices.

Supplies:
(The list is for 1 piece)

Parts
- 1x Breakout board for SOP28/TSSOP28 chip
- 1x ATTINY414 (you can use other microcontrollers and adapt it yourself)
- 7x 1k resistors (THT, 1/4 or 1/8 W)
- 1x 100nF capacitor (THT or SMD)
- 1x 0.56in common anode 7 segment display
- 1x Slide switch
- 1x Coin cell battery holder (I used CR2032 here.)
- Some AWG30 wires and resistor legs (for jumping in tight areas)
- Sticker or Double-sided tape (for covering the area to prevent shorting)
- 1mm shrink tube
- 1x keychain

Tools
- Soldering iron and smoke extractor
- Helping hands or PCB holder
- Small diameter solder (I used 0.025in.)
- RMA Flux
- Alcohol wipes or Isopropyl Alcohol + Flat brush
- Tissue paper
- Masking tape
- Microcontroller programmer (based on your MCU)”

Link to article

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