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Topic: using a momentary switch with dc-dc convertor to turn arduino on (Read 777 times) previous topic - next topic

dania25

I've picked up a dcp01b series TI DC-DC converter and I'm working on a circuit to use it with a momentary on/off switch to turn on an arduino (well, actually just an Atmega328).  By using the atmega's output pins to toggle ON pull up resistors (and an open drain on the other side of the switch) could I use this set up?  I can already see that when all power is off, the SYNC IN will be left floating, which I will need to address in the final design.


I'm trying to achieve battery efficiency over a wide range of voltages from ~4.5V to 6V using Alkaline batteries-

Maybe It will be simpler to reference the below schematic and technical data:

http://focus.ti.com/docs/prod/folders/print/dcp012415db.html



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dania25

Oops, see another problem!

When I push the button for OFF when sketch running, it will immediately stop the open drain on D4 and engage the P/U, keeping the system ON.  Hmmm, anyone with a bit more hardware experience have a suggestion on using a momentary pushbutton switch to toggle on/off state of chip? (without using an on/off switch!) I guess I could use 555s or something, but lots of devices have this, how do they do it and how do they avoid excessive OFF current consumption?

Graynomad

I had a quick look at the chip data sheet and don't see where it says you can use the SYNC input as an on/off.

Quote
open drain on D4

Arduino doesn't have any open drain pins AFAIK, (except the i2c pins). You can mimic that feature by swapping a pin from input to output though.
Rob Gray aka the GRAYnomad www.robgray.com

CrossRoads

Why not have a pulldown switch that goes to the interrupt pin - if the sketch is running and the interrupt occurs low (use the internal pullup on D2), then go into sleep more - and if in sleep mode and the interrupt occurs, wake up.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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dania25


Why not have a pulldown switch that goes to the interrupt pin - if the sketch is running and the interrupt occurs low (use the internal pullup on D2), then go into sleep more - and if in sleep mode and the interrupt occurs, wake up.


I was hoping to use the power supply sync to completely cut power to the chip, cutting the total consumed power to nearly zero, as this device will be in storage from time to time for periods of weeks.  On looking again at the schematic, yes, it doesn't say the SYNCIN pin can be used as a power switch, however, it also says that pulling it low will 'inactivate' the converter.  I didn't see any power consumption specs for the 'inactive' state, so maybe it isn't a stable state meant for periods longer than a high frequency cycle?

My current version of the schematic just has an open circuit on/off switch, but I would really like to use my nice surface mount buttons if possible! any ideas? I would like OFF power consumption to be <.1mA....

Thanks!

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