The Wireless Charging and Portable Raspberry Pi for under $10 dollars – in all its glory.
It ain’t pretty…
The concept works. But, technically it was sorted out in 2009 when the first Palm Pre came out. I, in fact, had a Palm Pre back then. Since then, Palm and WebOS has ingrained itself into me like the love of a childhood cartoon show. For all its flaws, you love it like nothing else.
It isn’t surprising I immediately went to the old Palm phones immediately when I started this project. (Fun fact: I started this project 3 years ago! It’s been on the back burned for a long time.)
This was a short build, despite the 3 year gap in development. I originally was going to make a wireless and portable Pi B+. Then it was a 2. Now a 3.
Luckily, power demands and mounting footprints stayed the same.
Although wireless charging, inductive charging technology has advanced a bit more since the palm days, I found the prices of such “Qi” charger kits to be a little high for my taste. But, since Palm/webOS phones are nearly gone… I figured it was the perfect time to pick up a bunch of the accessories.
In the end, I have what I wanted. It can stay off the charger for around 1hr with the single Palm Pre/Pixi battery. It charges and stays on and useable at all times. Super-happy success!
Here is what I bought for this project:
1 Palm external battery charger with extra battery
1 Palm Pixi Inductive charging back cover
1 Palm Touchstone wireless charger base kit
I bought all 3, with more accessories, as a group on eBay for $5.00 with free shipping.
Sources I used were Amazon and eBay. I also bought a HP Pre 3, the last webOS phone, just for fun. I am currently using it on the service “Ting.”
1 surface mount relay (pulled from electronic surplus)
1 Voltage boost regulator (Bought in a pack of 10, so $2 each)
Bits of breadboard (surplus)
Project wire (surplus)
Raspberry Pi 3
Adafruit GPIO 2.8” Touchscreen
3D printed parts (Printed on my printer for cents in material)
So… to add wireless charging and portability to a Raspberry Pi with a touchscreen… was below $10.
I win! Yay! …
But no one is keeping score…. Hmm
Problems I experienced in the build:
- I didn’t quite realize the size of some of the components I used. The breadboard (pieces) in particular were very large and made fitting all together look terrible.
- Likewise, the project wire I used were not able to be tucked, neatly, into the housing. So, wires spill out everywhere.
- Ultimately, the screen I used was way too small to do anything with it. Using a 5” screen would be way nicer.
- Using a cellphone battery is a big issue. On a lot of batteries there are 3, 4 or more contacts. They aren’t simple +5V and GND. No, some are thermal sensor contacts, among other uses. In this case, I had 3 contacts. The 3rd contact is a for a thermistor for internal battery temperature sensing. To charge the battery, and use it for power, I had to “trick” the battery into working. When the system in placed on the Palm Touchstone charger base, the relay is powered… connecting the thermal sensor contact to the battery’s negative. This was the BRUTE FORCE way I chose to make the battery charge when it was on the base. When you take it off, the relay would turn off, it would disconnect the thermal contact. Which was the only way I could force the battery to supply power to the Pi when off the base. If I left the thermal and battery neg connected, the battery wouldn’t supply power to the Pi when off the charger base, in other words.
- The battery charger needed 5V to charge. But then, it would only output the typical Lithium 3.7V to the Pi. I added the voltage boost circuit to then bump up the 3.V back to 5V. I either need to boost or buck a voltage no matter what I did. I just found it annoying, to be honest. The Pi should have a voltage regulator onboard, in my opinion. Take any voltage and use it.
If I continue to refine this project:
- Taking all the additional components and make a small PCB for them.
- Use modern wireless charger components. Which would affect the first refinement. With this, a much larger battery. The Palm Pre was 1125mAh, I would make the new one close to 5000mAh.
- Use a bigger screen, and in turn, a larger 3D printed case.
Schematic, block, diagram.
All the parts used in the project's build. Note: I soldered the power pins to the bottom of the Raspberry Pi GPIO. Why? The screen was covering up the pins.
One of the first tests. The Raspberry Pi is on and booted to the OS. The whole system is running off the battery.
The whole Wireless&Portable Raspberry Pi, charging, on the base. Yikes... that is one ugly mess. But it works!
See more of my project here: