SUPERDUPER low power!

Sniper King

OK, so I have finally been able to get extremely low power draw out of the Propeller (.007ma). Now what Voltage regulator do we use to keep that extremely low power?

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·- Ouch, thats not suppose to be hot!··


Michael King
Application Engineer
R&D
Digital Technology Group

Mike Green

What's your power source? What's the maximum you want to draw?

Paul Baker

Switching regulators are always more efficient than linear regulators. What type to use depends on what your using to power it.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Sniper King

Power source chosen is a 6v lantern battery with 11000 MAH charge.· To get the low power I dropped the clock speed to RCSLOW and I am waiting on a WAITPEQ statement that stops COG operation until PIN 3 goes high.· Upon activation the Propeller will "Wakeup" and the clock speed will go to a blazing 80MHZ drawing 30mA according to the Manual...
500 μA per MIPS (MIPS = Freq in MHz / 4 * Number of Active Cogs)
I have the Main program running·in COG 0 and the FullDuplexSerial object opens another COG so...
80000 / 4 * 2=20000uA
or 20mA
·I also have a PIR Sensor onboard that draws about 100uA and when activated draws 12 mA.
add 12ma to·the propeller draw·and we get a maximum draw of 32ma.· Add an OOPS factor and spiking and I imagine about 100ma would be a safe VR

.··

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·- Ouch, thats not suppose to be hot!··


Michael King
Application Engineer
R&D
Digital Technology Group

Paul Baker

With a 6V source you will want to use a Buck (aka step-down) switching regulator.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Sniper King

Are ther any part numbers out there for the dumb...LOL

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·- Ouch, thats not suppose to be hot!··


Michael King
Application Engineer
R&D
Digital Technology Group

Phil Pilgrim (PhiPi)

Paul,

If maximum power is drawn infrequently, the quiescent current required by a switching regulator circuit may disqualify it in favor of a "micropower" linear regulator. OTOH, if you charge up a supercap during maximum power periods, you could simply turn off the switcher during quiescent periods. You'd need some sort of fail-safe mechanism to force the switcher "on" if the supercap drained too far, though. Yet another option would be to employ both regulator types, automatically switching between the two, depending on the current draw, thus obviating the supercap.

Michael,

How were you able to measure a 7uA current draw? Do you know how accurate that measurment is?

-Phil

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'Still some PropSTICK Kit bare PCBs left!

Sniper King

Here is the code.· Real short and really simple.· We may get multiple hits one right after the other.

This is being used on the US/Mexico border to detect illegal immigrants so sometimes there are 20+ people in a line walking north.· The PIR sensor sends a 2 second pulse when activated.· That is what trips my WAITPEQ statement.· So we would see multiple activations from a single group.

{{
PIR UDA Sensor.spin, v1.1,Michael King
 ┌──────────────────────────────────────────┐
│ Copyright (c) 2008 Michael S. King       │               
│ See end of file for terms of use.        │      
└──────────────────────────────────────────┘
  }}
CON
CON
          _clkmode        = rcslow
        '_xinfreq        = 5_000_000
OBJ
        Clock : "Clock"
        Send : "FullDuplexSerial"
        
PUB main
dira[noparse][[/noparse]16]:=1
clkset(%00000001 , 0)                          ' Set internal oscillator to RCFast and set PLL to start
  waitcnt(cnt+120_000) 
                       ' Set internal oscillator to RCFast and set PLL to start
   
repeat
  waitpeq(%0100, %0100, 0)   'Wait port Port 3 to go high
         
  
    
  clkset( %01101000,80_000_000 )
  waitcnt(800000+cnt) 
  clkset( %01101111,80_000_000 )
   waitcnt(800000+cnt) 
   outa[noparse][[/noparse]16]:=1    
  
  
  send.start(31,30,0,9600)  ' start FullDuplexSerial
  waitcnt(20_000_000+cnt)   'Wait a bit for the XTEND to be ready
  send.str(string("<*00000001*S*>")) 'Send activation of sensor Message
  waitcnt(20_000_000+cnt)   ' Wait for message to be sent
  send.stop
  outa[noparse][[/noparse]16]:=0
  clkset(%00000001 , 0)                          ' Set internal oscillator to RCFast and set PLL to start
  waitcnt(cnt+5_000) 
  

It should be on for no more than 2 seconds.

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·- Ouch, thats not suppose to be hot!··


Michael King
Application Engineer
R&D
Digital Technology Group

Paul Baker

Thats true the efficiency of switchers for micropower apps can be dismally low.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Sniper King

I have never used switching power supplies are they hard to implement?

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·- Ouch, thats not suppose to be hot!··


Michael King
Application Engineer
R&D
Digital Technology Group

Paul Baker

If you're not careful with your design they can be an absolute pain, but they are rather simple once you figure it out. I would get one of the few chips that is still availible in DIP, something like the LM2594N-3.3.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.