Juice4Halt – Supercapacitor UPS for Raspberry Pi
When we started thinking about using the Raspberry Pi in applications requiring a bit more reliable operation, we always had to face the same problems:
- Power outages
- Corrupted file systems or SD-cards
- Inrush currents
As a solution to these problems, we have created the Juice4Halt module. It combines brownout protection and a short-term UPS for properly shutting down the Raspberry Pi. Instead of a conventional battery, the module uses two supercapacitors.
The advantages of using supercapacitors
- wide temperature range
- no maintenance
- long lifetime
- no mechanical contacts
- uncomplicated transportation
- no environmental issues
The Juice4Halt module is a supercapacitor based energy storage. Combined with a Raspberry Pi (Model B, OS Raspbian) it offers:
- 1 minute backup time for a safe shutdown
- 12 seconds protection against short-term power failure or brown-out
- high reliability of operation with peripheral devices attached to the 5V supply output. No risk of voltage drops on the power rail (e.g. at hard drive start up)
Communication with Raspberry Pi
The standard handshake between the Juice4Halt module (J4H) and the Raspberry Pi (RPi) requires the I2C-bus interface and the GPIO25 pin. There is a script file running in the RPi background. If you don’t want to use the GPIO25 and the I2C-bus there are other options too (e.g. only GPIO25, only I2C-bus, UART, SPI)
DC power connector
Type: Barrel power plug 0.7 x 2.35mm
e.g.: Digi-Key part number: CP-012-ND
The Juice4Halt module is stacked on the Raspberry Pi board using a 2×13 pin stacking GPIO header:
a) Stacking height 13.6mm (e.g. Adafruit ID: 1112)
b) Stacking height 8.5mm (e.g. Samtec SSQ-120-03-F-D)
Operating in shock and vibration environments requires making use of the 3mm mounting hole. The mounting hole and the push-button share the same space on the board. So when using the mounting hole, the push-button option is not available. Additionally, the supercapacitors have to be fixed to withstand the environment influence.
In embedded setups, the Juice4Halt module can be placed on a carrier board and soldered using the edge plated contacts at the sides of the module.
Supercapacitor assembly variants
There are several ways how to assemble the two supercapacitors:
- Depending on the distance between the Juice4Halt board and the Raspberry Pi board, the supercapacitors can be assembled on the top side or on the bottom side of the board – whatever makes the two stacked boards more compact. There are two types of GPIO headers which lead to different stacking heights (13.6mm or 8.5mm).
The assembly position of the supercapacitors is different for the Raspberry Pi B Model and B+ Model.
If you are not sure, no problem: You can choose the DIY version instead of the PLUG&PLAY version and solder the two supercapacitors yourself to fit exactly to your needs.
Personalize Your Juice4Halt
You like the Juice4Halt, but you would prefer using another pin for communication at the GPIO interface? Or do you want to have your own connectors assembled? No matter!
Just download the circuit diagram, choose the perk “Personalize Your Juice4Halt“ and tell us what components you want to have changed. We will modify your Juice4Halt and you don’t have to solder the parts yourself.
There is just one condition: We have to review your change and we must agree with it. This is just to protect your project from failure.
And the components? We will cover the cost of materials up to a value of 50 cents. That means if you want to have a few resistors changed, we will not charge you for it. However, if you want to have a connector changed, we have to agree on the price beforehand.
For more detail: Juice4Halt – Supercapacitor UPS for Raspberry Pi