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• status2

  Robert Mateja • 01/08/2018 at 21:54 • 0 comments

  spark dispenser waits for mosfet and it's low voltage driver

  imagine Pratchett an Catch-22 combined in customs office - that's what i'm dealing now :)  so a little delay on this project

• Day one on potential well - how to talk to your kids about electrons

  Robert Mateja • 12/06/2017 at 22:08 • 0 comments

  Due to fast crash on modern art market I loose interest in sketching. Fortunately my exquisite skill stayed with me, and now i can share it with the rest of the world.

  Below is analog representation of author momentary imagination.

  Coin cell powered spot welder. Clearly symptom of troubled mind.Nevertheless, preliminary calculation looks promising so bear with me for a while.

  CR2032 has 220mAh of umpf to share, at 3mA/h rate (assumption based on  datasheet curves).That's 3.6 Coulombs.

  Assume that drawing that much current (3mA) in that moment, will drop 

  battery voltage to 2V (again from datasheet curves).

  1Coulomb x 1Volt = 1joule

  3.6C x 2V = 7.2J    <---  our energy umpf budget per second from single 

  coin cell

  Now we have to find a bucket and a hose to pump it and hold.As famous 

  fun killers Clausius and Carnot tells you, there is always a few holes.

  I hear you! Don't worry, we have time to talk about ultracaps and big, 

  fat copper highways.Just look for a second at our goal here.

  Best way to join two parties that don't get along, is to send a two 

  platoons of succes hungry, angry pixies down the road.They melt all the 

  resistance in their way and leave strong bond.Howewer to do it, you need 

  to provide energy.How much you ask? Man that's a good question, let's 

  interrogate science lady.

  Standard li-ion cell has terminals made of stainless steel,copper or 

  aluminium plated with nickel.Most spot welds strips are made of nickel 

  or - when god of Shenzhen is not merciful this week - steel plated with 

  nickel. So basic idea is to poke sharpened sticks of metal on top of 

  nickel strip on top of nickel cell tab, you get the idea - turtles all 

  the way down.

  Then send anger thru angel of Volta - a humble, trusted mosfet, to melt the two together.

  All that carnage is happening on relative small area.Depending on your poke sticks, I would say a circle with 1mm in diameter 

  (a.k.a 0.03937 inches, 4.971×10^-6 furlongs or 0.003281 feet,  simple).

  Adding 0.5mm strip thickness and 0.5mm cell tab melt depth,  we got ~ 0.786 cubic millimeter metal volume to melt at one shoot.

  0.786mm^3 Ni  <--- how much energy then?

  Oh boy, that's a time in our story to call Captain WA. 

  https://www.wolframalpha.com/input/?i=heat+0.786mm%5E3+nickel+from+25degC+to+1455degC
  

  Asked politely, Captain says:
  

  nickel mass of 0.786mm^3  =  7mg
  melting point  =  1455 degC

  and a true gem:
  
  

  energy required to heat to melting point (from 25C):  0.00445kj
  + energy required to convert to liquid: 0.00205kj
  total umpf:   0.0065kj  =  6.5 joules!

  That's in our budget! On next episode: Thermal IRS on conduction tax. Stay tuned!

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