This week’s blog post comes from Mike, one of Dayton’s many makers. Since Pi Day was Tuesday, a Raspberry Pi project seemed appropriate!
When I originally bought my Raspberry Pi, I had primarily thought of using it as a Retro Pi; I figured it would be fun to play the games of my childhood with my kids. Pretty quickly though, I became interested in the other possibilities of the Pi, and I started playing with the Sense Hat, turning it into a media center, and a few other projects that are out there for the Pi. But, what I discovered is that, if I wanted to work on it away from home, it wasn’t very convenient. So, I decided to make it more portable.
First things first, I needed a container for the electronics. A family trip to the local antiques mall yielded up a very nice, wooden cigar box. With that acquired, I started looking around for a tutorial online for what I wanted to do. Adafruit has a good outline for this, as well as several YouTube makers. Ultimately, I came up with the following layout for the electronics:
The Pi consumes around 1-2 Watts under normal use. This requires about ½ Amp from the Li-ion cells. With two Li-ion cells (2.2 Ah each), the Pi should last around 8 hours. I haven’t tested this yet, though.
Additionally, the LCD screen consumes about 5 Watts. This requires about 1.4 Amps from the Li-ion cells. This may be pushing capability of TP4056, I really don’t know. That is why I don’t recommend charging batteries while using the screen. The TP4056 likely can’t handle the amperage required to do both simultaneously. With four Li-ion cells (2.2 Ah each), the LCD screen should last around 6 hours. I haven’t tested this.
There are a few quirks to this design. First, the Pi and the display run from two separate power supplies, which is the reason for the two toggle switches. I suspect that I would be able to combine them so that everything runs from one supply. Also, the display controller I bought doesn’t allow me to dim the display backlight, but advanced users might be able to do this from the Pi via pulse width modulation.