beyond the energizer bunny

 

The Internet of Things Doesn't Exist -

 

The other day I gave a conjecture talk on some possible architectures and evolutions of networking and computation to support densely deployed sensors and actuators. There are times when you resort to catchy title to attract an audience.  This was successful in filling the room.¹

 

One faces a variety of challenges with power being a dominant issue for many of the use cases you might dream up.  You find yourself talking in terms of nano and even pico-joules per bit of communication with device power drains in the microamp range. A smartwatch is a Humvee compared to a bicycle by comparison.

 

To get everyone’s attention I mentioned the Clarendon Dry Pile at Oxford's Clarendon Laboratory (if you’re into this history of science, this is a must visit). It consists of two dry pile batteries with a metal ball on a pendulum wire. Two metal bells are at the ends of the ball’s swing. The charged ball swings to a bell, transferring change and then is attracted to the other as the balance of charge has changed. Twice a second there is a ding. The power drain is small and the amount of energy stored in the battery comparatively large. It also turns out the chemistry, which is not perfectly known, is very robust.

 

Twice a second, 3600 seconds a day, 365.26 days a year. It started ringing in 1840 and continues to this day 175 years later.

 

Some details — batteries are stacks of about 2,000 Zn foil and MnO₂ impregnated paper disc pairs connected in series. Each cell generates about a volt, so each battery is about 2,000 volts. There is a coating to keep the moisture content stable - as the electrolyte is just water. The current is very low - about a nano amp so the power is a couple of microwatts. If you work through the arithmetic about 11,000 joules of energy have been delivered over the years. The battery in an iPhone 5s stores a bit under 18,000 joules. Estimates of the energy storage of the dry pile and its leakage are such that the bell should ring for at least several more centuries.

 

This type of battery is an odd duck - it has found use in some odd applications, but its high voltage low power characteristic coupled with an extremely poor energy density saw it replaced by more appropriate chemistries.  

 

A beautiful example of how demonstrations just past the limits of human lifespans - the properties of the pitch once used to waterproof boats and a light in a California firehouse -  fire the imagination.   I'm sure people in the audience will remember the battery better than what I had to say about what they came to hear.

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¹ Fundamentally the Internet is not hardware - that gets into a variety of topics that would have me writing for hours.

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Recipe Corner

 

A vegan West African vegan dish from Nigeria with some modifications to fit my ingredients.  I have no idea what it is supposed to be like, but this is definitely worth repeating.  Other dried fruit would work well - I'll try cherries next time.  Adding some nuts might be interesting too...

 

West African Rice

 

Ingredients

 

° 1 cup black-eyed peas

° 1 cup water

° cooking oil (3 or 4 tbl)  I used an olive oil, but.. whatever you have

° 1 medium onion, chopped

° 3 cloves garlic, minced

° 1/2 tsp salt

° 1/2tsp ground cloves

° 1/2 tsp ground cinnamon

° 1/2 tsp ground cumin

° 5 cardamom pods , seeds out and pods crushed

° 1 cup basmati rice

° 2 cups vegetable broth

° 2 - 3 tbl raisins

 

Technique

 

° preheat oven to 350°F

° put the water in a pan with the peas and bring to a full boil for about five 

° drain the peas and put them in a bowl

° put some oil in a pan (say the one you just used) and bring to medium heat - and the onion.

° When the onions are soft add the salt and spices.  Cook for three minutes stirring constantly.  Wow the aroma is amazing.

° Mix in the peas and add the rice and vegetable stock

° crank the heat to high until you have a boil and then back off to medium high.

° stir gently until the liquid is absorbed

° stir in the raisins

° transfer to a covered cooking dish.  Cover tightly with aluminum foil for a good seal and then cover

° bake for 45 minutes