I was watching a film and seen someone using a magic 8 ball, I thought to myself wouldn’t it be cool to make a digital one. So I went to my parts draws and seen if I had anything on hand to make it since the current pandemic I didn’t want to order anything unnecessarily. I pulled out a 3 axes gyro a nokia 5110 screen and a arduino pro mini and got to work. Join me below to see how I pulled it off.
- Arduino pro mini
- GX-12 male connector
- MMA7660 3 axes gyro
- Nokia 5110/3310 screen (PCD8544)
- TP4056 lipo battery charger
- DD0505MD (DC DC 5V boost)
- 14500 lipo battery
I have had this screen in my parts bin for some time, When I first pulled it out I wondered why I hadn’t used it in the past. After powering it on and finding the current library I was greeted with why I hadn’t used it be, Contrast and the need for external components. I found this Adafruit nokia 5110 screen Library, I seen that there was a way to use a potentiometer on the analog pin. I decided to use the gyro to set the contrast level, In a setting menu if you tilted it to the left it made the value go down and if you tilted it to the right it would go up. I added a button so when you press it it saves the current value to the eeprom.
I didn’t just want to navigate the menu with buttons because that would be boring. I thought why not use the gyro to navigate the menu which worked out quite well, I made it so you tilt it to the left got you into the contrast menu so It was easy to do if the contrast had gone wildly out of whack. I just used UP, DOWN, LEFT and RIGHT to pick the different apps I had made. Here is the library I used
My first idea was to make a magic 8 ball but I thought I might as well add a few more apps. I made a dice app which randomly picks between 1 – 6. I made a YES NO app for when you can decide on what to do. I can add more as I need to.
The problem with my projects is I always put a lipo battery in them, I then don’t use them for awhile so they go flat or go bad. With this project I wanted the battery to be removable so I wouldn’t go bad and can be used in a different project. I have already designed a 14500 battery holder but I needed to design a battery bay complete with door. My first attempt was overly complicated and bulky so I redesigned it. I can then import this design into different projects.
The lid idea was to use a magnet but I hate using external parts so I decided to use tangs to clip into the battery bay. The first lid wasn’t 3d printer friendly so I redesigned it so it could be printed flat.
It ended up working quite well but It does limit the design because the battery bay has to be exposed on the top because I did try and print it on its side and didn’t quite turn out right
Power without a PCB
This is also a first, I didn’t want to add the power circuity to the main PCB because It makes the PCB bigger and cost more. If I could incorporate the TP4056 lipo battery charger and DD0505MD boost into the 3D printed design so It wouldn’t cost me a thing.
I made it so the 2 board would be held in place and then soldered together with solid core wire to cut down the bulk. I can import this into my designs when I need it.
Rework and bad board design
I had a disaster with this project. After I had assembled the board I dropped it on the hard floor, After that the screen wouldn’t work. At first I thought it must be the screen so I re-flowed the screen pins but that didn’t fix it. The problem with the layout I had used was to save space I mounted the screen over the arduino. I had to de-solder the screen to get at the arduino, I re-flowed the solder joints there to see if that would fix the problem but it didn’t. I had used a new arduino for this project so I still had my one I used for breadboarding which hooked back up to the screen worked. I had to de-solder the pins on it because I had used SMD pad on the PCB. While pulling the pins out of the board I had caused the VCC and GND to become shorted mid board. The only thing to do was order a new arduino but I haven’t got time for that. I decided to try and pull the chip off the shorted board and transplant it onto the original dead arduino. I got my hot air station out and applied some flux, To my surprise it worked the only pin I had to touch up was the reset pin.
Normally I wouldn’t have gone to this extent but with a new arduino about a week away I just gave it a shot. What this pandemic has taught me is to be more experimental and to be more resourceful
I’ve been adding lanyard holes to my projects because you never know when and where you will use it.
Thingiverse – https://www.thingiverse.com/thing:4422273