Update: August 11th, 2019
I have been gathering parts and components to get this project going and my apologies for updates being so few and far between.
The Tricorder itself you can get on Ebay pretty cheap since they manufactured a ton of these. Think I paid around $15 for mine. They are cheaply made with very little circuitry. It has 2 LEDs, a tiny speaker, couple of C9013 PNPs, couple of resistors, and of course the black blob that is "Chip on Board."
The most difficult aspect is going to be the LCD. I purchased a Chinese MP3/MP4 player ($12 on Ebay) will try and hack it enough to play videos with a few buttons. The player has the default tactile buttons for control. I will be using regular panel buttons on the Tricorder body so I will need to add wires to the button circuit so we can have control of play back.
Refer to the image and you can see how I soldered a ribbon cable to the button pads of the mp4 player. This will alow me to place regular momentary buttons anywhere on the case to control the player.
Update: September 23, 2019
Made some progress on the tricorder, It's not much but it's something. I started breadboarding the circuit and added the LCD. Like I said, it's not much but it's progress none-the-less. The LEDs are controlled by a TLC5940 with a generic code. Still have some work to do before going to the next step which would be adding more LEDs and also having the ATmega controlling the LCD screen directly.
Update: January 11th, 2020
Sorry for the amount of time between updates. Life always finds a way to get in the way. Anyway, I prototyped the LED circuit using the TLC5940 and added the Ebay mp4 player that will be used as the tricorder screen. I've had no issues driving the 5940. Right now it's just running the example code that's provided with the library.
On the other hand, the LCD is giving me issues. The buttons for the mp4 player is used to scroll through the menu and to start playing video. They operate with active LOW. But, when I try to set pins to LOW then HIGH to simulate button presses, the player shuts off. I did some troubleshooting and found that the buttons are at ~1.5V when not activated (not grounded). So when I set a pin back to HIGH, the Arduino is drving the button to ~3.9V. Note that I am planning on using a single cell LiPo to power the tricorder which runs between 3.5V and 4.2V. So my next goal is to use a voltage divider to bring the button voltage to where it likes it. I'm still not convinced that this will solve my power off issue though.
Once I deal with that, I will be adding the sound circuit along with the charging circuit.
Update: January 26th, 2020
Little update, I damaged one of the pins on the cheap mp4 player and had to order another. But I did get a better one! So I found out the hard way that the buttons are at a different voltage level than the rest of the system. Even though the system is powered by a LiPo battery which is 4.2V at full charge, the controller's IO pins are at a 1.8V level. So by controlling these buttons with a 3.3V logic level wasn't a good idea.
Now that I have a little more knowledge, I will use a simple voltage divider provided by resistors to get that 3.3V down to 1.8V.
On another note, I did start ordering some of the other parts, the square LEDs. Since the cutouts on the tricorder body are quare, I needed square LEDs. They are a little more expensive but should give good results. I'll post some pics and vids soon.