Need IC that pulses every few seconds - Page 1
Forum section: electronics / projects

author: seeigecannon
author_rank: Newbie
timestamp: August 01, 2016, 02:46:23 pm
content: I am working on a battery operated device, and I want it to be able to last as long as possible. I am putting the MCU into idle, but it is still taking way more power than I would want it to. I would love to be able to put it into full-fledged sleep mode, but it cant wake itself up again without an external interrupt.Is there an IC I can use that pulses once a second or once every few seconds, but doesn't need many external components and takes very little power? I would like to use that to trigger an interrupt. Thanks.

author: MosherIV
author_rank: Super Contributor
timestamp: August 01, 2016, 02:51:26 pm
content: QuoteErm, you want to be using a timer peripheral built in the microcontroller, they can generate a regular timed interrupt.QuoteAlternatively, I would suggest the good old 555 timer, try a CMOS variant for extra low power.

author: Marco
author_rank: Super Contributor
timestamp: August 01, 2016, 03:04:29 pm
content: http://www.discovercircuits.com/DJ-Circuits/3NAOSC1.htm

author: StillTrying
author_rank: Super Contributor
timestamp: August 01, 2016, 03:10:13 pm
content: Quote from: seeigecannon on August 01, 2016, 02:46:23 pmIts watchdog timer.Or an RC on one of it's pins that charges or discharges when it's asleep.

author: Ian.M
author_rank: Super Contributor
timestamp: August 01, 2016, 03:25:17 pm
content: Which MCU?

author: Fungus
author_rank: Super Contributor
timestamp: August 01, 2016, 03:58:06 pm
content: An Atmel ATtiny85 will do it.I've made things that run on a Tiny85 for years using a single coin cell. They wake up every now and again and do something. Making a pulse every few seconds would be easy.Edit: And so will an Atmel Mega328 - all Atmel AVR chips can sleep on microamps and wake themselves up periodically. I only mentioned the Tiny85 because they're small and I've built lots of coin-cell devices with them.

author: TiN
author_rank: Super Contributor
timestamp: August 01, 2016, 04:08:44 pm
content: Linear TimerBloxif 3$ and 300(800)nA fine for you

author: seeigecannon
author_rank: Newbie
timestamp: August 01, 2016, 05:38:59 pm
content: Thanks for the replies. I am using an internal timer right now, but when I go into the full-on power savings mode the timer gets shut off and requires an external interrupt to get things kicked off again.I am using a stripped down Arduino Pro Mini, so an ATMEGA328 MCU. I unsoldered the LEDs and removed the regulator and am running it strait off a 3.6V battery.I did consider a 555, but I was worried about current draw, I can look into how low I can get it though. I am also worried about anything with a moderate component count as I am gluing all of the components to the bottom of the Arduino board dead-bug style.

author: JPortici
author_rank: Super Contributor
timestamp: August 01, 2016, 05:39:29 pm
content: Read the datasheet of your MCU.The power saving chapter.Unless you are using a 20 years old pic or something you will have a number of options to get the cpu out of sleep by timers and/or interrupts.And if you are using a 20 years old pic or something all those options will reset the mcu or trigger the interrupt so you just need to set a register/bit to chech whenever a reset or interrupt was fired by exiting from sleep, so your program act accordingly

author: hans
author_rank: Super Contributor
timestamp: August 01, 2016, 05:44:27 pm
content: You can use the watchdog timer to wake up the chip periodically. See page 39 of datasheet.On some newer devices you may also have a RTC or RTCC that can wake up the chip for a given amount of ticks, or at a specific time/date.There is absolutely no need to use an external timer chip for this.I'd suggest looking around in some of the IoT libraries for their sleep/power management functions, or write your own with the datasheet on the power management/watchdog pages in hand. I believe JeeNode had a wonderfully simple to use sleepy function that slept the micro for an approximate amount of ms.

author: seeigecannon
author_rank: Newbie
timestamp: August 01, 2016, 05:53:44 pm
content: Quote from: hans on August 01, 2016, 05:44:27 pmThanks. Found a tutorial herehttp://donalmorrissey.blogspot.com/2010/04/sleeping-arduino-part-5-wake-up-via.htmlthat looks like it will do everything I could want. No more external parts for me.

author: seeigecannon
author_rank: Newbie
timestamp: August 01, 2016, 10:24:13 pm
content: You guys are awesome. I was shooting for about a year of battery life and a quick calculation says that I should have about 5. All this with no external hardware. Thanks.