Whilst Hans was busy coding, Matilda was looking into power requirements. She was worried that the batteries might take a long time to deliver so wanted to order them long before they would be needed.


DevicePower Required
Arduino Yun300mA
MicroSD Card100mA
Infineon RGB LED controller9mA
RGB LED 20mA per colour60mA


Totting up the numbers she arrived at 569mA peak consumption, she realised that by turning things off and running tasks in series that number could be reduced. She also concluded that if they only checked the weather a few times an hour then their overall consumption could be reduced too.



Based on these numbers she concluded that a 2000mAh battery would give them several days run time. She would need to measure the actual consumption once the circuits were assembled.

Given the small size of the cottage, a Lithium Polymer battery gave the best size to capacity, it was also easily capable of providing the peak power requirements. The PowerBoost 500 from Adafruit was selected to charge the battery and also boost the 3.7v of the battery up to 5v needed by the Yun.


The Flaming Postman

The next morning Matilda was telling the postman about her purchase and he explained that they could not deliver her battery. They'd stopped taking LiPo batteries after that time when old Bob's hair caught fire after a battery exploded in his sack. He was half way to the next village before someone caught up with him and helped put out the fire. "I smelt something but thought it was that pudding lane pie shop" he had said.


The blind man and a trip to the market

Matilda would need to collect the battery herself so grabbed her basket and headed off to the market. On the way to the market she met and old blind man carrying a basket of apples. She walked with him for sometime and chatted about the work on the cottage. As they approached the market some small boys ran up and each took apples from the man's basket, the old blind man appeared not to notice so Matilda shouted at the boys. Matilda apologised to the old blind man that she could not stop them. "I used to wave my stick at them" explained the old blind man "but that was very tiring, so now I just wear this blindfold so I don't have to watch them taking my apples". "So you're not actually blind then?" asked Matilda. "Oh, no dear", said the old man with a blindfold. Matilda said farewell and popped into the supply office to collect her battery.


When Matilda returned from the market with the battery she found Hans still struggling to get the appropriate modules to compile for secure python requests. "Can you believe that everyone just recommends turning off the warning messages" exclaimed Hans. Yes, Matilda could.


Next: Enchanted Objects Design Challenge - The Blue Haired Woman and Off Grid Living