Ever since the storm Hans and Matilda's power supply had been quite flaky. The electricity company had sent engineers round several times who found and fixed loose connectors and faulty wiring deep in the forest. But the problems kept occurring so Matilda was keen to get their battery based supply up and running.



The Blue Haired Woman


On the day that Matilda planned to connect up the Yun they had a knock on the door. Hans opened the door and was greeted by a large blue ball of fur, carrying a pie. "Hello Hans" said Mrs Spratt's voice from inside the ball. Hans invited her in and they went through to the kitchen where Matilda was busy soldering. A space was cleared for the pie and Hans found a knife and plates so they could all have a piece. Mrs Spratt explained that she'd found an old shampoo recipe made from blueberries that was supposed to make your hair stronger and full bodied. It was not till after she tried it out that she read that it sometimes had side effects. She'd had a few berries left over so had decided to make a pie for Hans and Matilda. Mrs Spratt had been eating whilst she was talking so Hans washed up the empty pie dish and Mrs Spratt took it home.


Off Grid Living


Matilda was keen not to have any unexpected side effects with her battery and power so she built a simple circuit on the breadboard to test it.


The AdaFruit board that has been selected provides 5.2v rather than 5v so the schematic was examined and each of the datasheets checked to avoid an expensive mistake.


ComponentData Sheet
Max Supply Voltage
RT8010 - 3.3v Regulator for the MIPS Processorhttp://www.richtek.com/download_ds.jsp?s=2825.5v
MAX3375E - Bridge Level Shifterhttp://www.maximintegrated.com/en/products/interface/level-translators/MAX3375E.html/tb_tab05.5v
NTB0104 - ICSP Level ShifterNTB0104UK :: NXP Semiconductors5.5v
NTB0102GF - Handshake Level ShifterNTB0102GF :: NXP Semiconductors5.5v
AU6350 - USB hub and card Readerhttp://wenku.baidu.com/view/6c347a4ac850ad02de8041905.5v


The voltage across the LED and resistor were measured and was around 5.1v so comfortably in the range of all of these components.


Mounting the Yún


There are several engineering drawings for the Arduino series explaining where the holes are located, it's also possible to use a board as a template to mark the holes. After looking at a selection mounting plates on Thingiverse, Matilda decided to go for 3mm threaded rods, captive nuts and some spacers.




The Arduino Yún provided it's own challenges here. The SD card is right next to the mounting hole so makes it difficult to put in a spacer. The height of the 90° USB and Network sockets are particularly high so long pins are needed. The stacking headers found from CPC did not have enough clearance so were swapped those with the long pins provided in the kit and then soldered the shortened stacking headers on top. The Infineon board could then be used with standard length pins.


The protoshield also threw in it's own curveball having only 3 out of the 4 standard mounting holes. With the test fitting it's fairly sturdy so one of the screw threads can be shortened to just support the Yún.


The battery will also need mounting somewhere, perhaps a battery box strapped to the back of the house? This is also a challenge as the pre-wired cable is quite short.


The Wolf


Meanwhile in the forest the wolf put away his wire cutters and realised he'd need to find another way to sabotage the project.


Next: Enchanted Objects Design Challenge - Hans meets "Injector"