Power switch

iseries

Has anyone designed a power switch that works like a tablet switch.

For example if you push the switch it powers on the Propeller and if you hold the switch for five seconds it powers itself off.

I have not seen any project like this and would like to build one. I thought of using a couple of MOS Fet switches to do the work.
The Propeller could also start a watch dog timer and if there is no activity it could power it's self off.

Mike

tonyp12

Tablets & phones uses a Supervisor Reset Switch, as having to relay on the mcu to reset itself from a input is not 100% foolproof in case it hangs.

http://www.mouser.com/Semiconductors/Power-Management-ICs/Supervisory-Circuits/_/N-wnws/?Ns=Pricing|0

iseries

While this device provide protection from the processor depleting the battery it is not a solution to providing a power on circuit.

Mike

yeti

I have no idea about pros and cons of this solution.

Can someone here comment it?

idbruce

iseries

I am not exactly sure how a tablet switch works, but I think this is what you might be looking for... forums.parallax.com/discussion/156184/discussion-of-latching-a-momentary-switch-to-control-a-power-supply#latest

tonyp12

The link is for all supervisor, there are 3 category's of supervisor ic's: voltage, watchdog timer & switch reset.
The one that powers up the tablet with a simple push and reset it if you hold it down for 6seconds is there.

I sorted all by price, so keep looking until the first one does just that.
you learn something from looking at all those data sheets too.
Very tiny as for latest smartphones:
http://www.mouser.com/ProductDetail/Torex-Semiconductor/XC6190AN157R-G/?qs=sGAEpiMZZMunEhqKs81nFPBhTyRLN/sACxAqNzxo6yU=
http://www.mouser.com/ProductDetail/Microchip-Technology-Micrel/MIC2782DRYCS-TR/?qs=sGAEpiMZZMunEhqKs81nFLHEzlgNxanPcc/kqIIy9mo=

Some of them are in the Clock & Timer ICs category, this could work:
http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/FT3001MPX/?qs=sGAEpiMZZMsFq5dYAzx%2bAP98CwVzF87p1If7c/bJGf0=

iseries

I was thinking of something a little simpler. Like the following:

On one side would be the Propeller such as pin 0. On the other side would be a momentary switch.

When pushed it would power on the Propeller and in code would make pin 0 high turning on the second fet.

when the button is released the unit would stay powered on. At any point the Propeller could power itself off.

Mike

kwinn

Don't need a second fet. Propeller pin goes to gate and push button across fet provides power long enough for propeller to boot and output signal to keep fet on.

T Chap

Here is what I did. This board requires 3 different voltages. One of the voltages is 3v3 for the main propeller section. There is a button labeled "Mode" that has several functions. You can press it to turn on the power (hardwire enables power ENA on the 3v3 Reg which then powers up the Prop which then holds itself ON). If pressed and held, a timer starts counting to see how long it was pressed, if long enough a Prop pin holding the regulator ENA High will then shut off. This uses a bi polar mosfet. The Mode button gets it's power source direct from the battery.

PUB PowerDown  | counter
  outa[22..24] := %100   'main power reg ena, dac V reg ena, flash V reg ena
  dira[22..24] := %100
  dira[19]~~  
  
  Repeat
   if ina[FlashBut] == 0
      counter~
      bp   ' beep
      blink1   ' flash led
      repeat while ina[FlashBut] == 0
          counter++
          if counter > 100000
             Dive  ' make beep sequence t indicate power off
             outa[22..24] := %000

iseries

The reason for the two Fets is that the switch is tied to a pin say pin 1 that is used as input to determine if it should shutdown if already powered up. IE this would be an external power on power off switch with the Propeller in a case.

I was also thinking that I might need some RC circuit so that if a reset were to occur it would hold the pin high long enough for the Propeller to boot up and take over again.

Mike

tonyp12

And after you add all those parts, one of the single chip I mention probably seems like the smart move.

Could you reset system hang if you by mistake pull the pin low the first thing during boot up?
a endless reset cycle there you can not get in to reprogram the firmware? (until you desolder a part)

That is why tablet and phone manufactory use these reboot ic's

iseries

I looked at some of those solutions and they are not a solution but only a piece of the puzzle. The only provide a reset mechanism and do not power anything.

I can purchase two MOS fets for $.50.

Mike

tonyp12

If you want to turn power off, go to the source, get a LDO with shutdown.

TI also have power gating IC's
http://www.mouser.com/Search/Refine.aspx?Keyword=TPL5

For LDO with PG (powergood)
http://www.mouser.com/ProductDetail/Texas-Instruments/TPL5000DGSR/?qs=sGAEpiMZZMvARmQSk64rF8ksTkAGkThd

For LDO with Enable
http://www.mouser.com/ProductDetail/Texas-Instruments/TPL5111DDCR/?qs=sGAEpiMZZMvdy8WAlGWLcDBFGpzDUAXiydVgRsRjRxc=

erco

@tonyp12 :

You're a freaking rock star, I learn tons from your many posts. Thanks for carin' & sharin'.

MikeDYur

If you didn't want to get too involved,

Pololu has FET soft switches:

https://www.pololu.com/category/121/pololu-power-switches

WBA Consulting

Dang, Mike just beat me.... My fav:
https://www.pololu.com/product/751

Ron Czapala

WBA Consulting wrote: »

Dang, Mike just beat me.... My fav:
https://www.pololu.com/product/751

FYI - Today is last day of Pololu's Memorial Day sale - the above mentioned switches are on sale 15% off

https://www.pololu.com/category/153/memorial-day-2017-sale

Publison

Ron Czapala wrote: »

WBA Consulting wrote: »

Dang, Mike just beat me.... My fav:
https://www.pololu.com/product/751

FYI - Today is last day of Pololu's Memorial Day sale - the above mentioned switches are on sale 15% off

https://www.pololu.com/category/153/memorial-day-2017-sale

OH NO YOU DINT send me to yet another Memorial Day sale. My Plastic is a hurtin'.