sleep for stand alone uno

i search the many pages of the forum and did not find anything related to my issue so i am asking.

i have designed, built, programmed a project that works but have an idea to add sleep instead of turning on and off with power.

project: 3 temp sensor controlled relays with adjustable set points and atmega328p, 20x2 lcd.

i am using in truck stereo system for amps attached to system power. instead of turning system on and off for listening and arduino being on same power line getting turned on and off, is it possible to leave constant power to 328p and do sleep function until stereo powered up again to wake 328p? is there any benefits to the sleep or leaving the 328p switched with system the better?

is it possible to leave constant power to 328p and do sleep function until stereo powered up again to wake 328p? is there any benefits to the sleep or leaving the 328p switched with system the better?

Yes it possible , sleep the arduino and then wake up using an external interrupt on either pin2 or pin3.

JUST MAKE SURE TO ADD A 5V ZENER DIODE OF VOLTAGE DEVIDER OR SOMETHING TO REDUCE THE 12V TO 5V.

thanx for replies, really appreciate info, especially for a nub to arduino.

next question you guys made me think of saying it is possible.

I want to retain settings from being powered up initially, sleep, woke up …
if I power_down, will it retain settings??? or should I use standby?

the circuit is running off my secondary battery bank so not really crucial for draining but don’t want to have low cells every morning to charge back up. I have default setting of 90 deg F but will most likely be adjusting so if I ‘power down’ the 328p, I want to retain the set point instead of having to reset each time it wakes. being power down is most saving, that would be great to use.

ok, I have one more question, I lied.

I also have three separate pcb’s. 2 have 5v reg’s and third is just lcd and buttons ribboned from main board.
being I am using the same 12v (14.5V) from battery string do I need to loop the boards together with the power feeds?
power in to main board and out from main board to next, or being same power will the ground (negative) be same with separate board power feeds.

I have a main power rail in the back with power line to radio up front. im thinking the return bar will carry over from one board to next without having to loop power feeds. I have attached a sketchy sketch of existing power supply I ‘think’ (help us all) should work.

disclaimer:
I don’t hold myself responsible if there should be more dimly light bulbs going off for further question… TIA

I have a main power rail in the back with power line to radio up front. im thinking the return bar will carry over from one board to next without having to loop power feeds. I have attached a sketchy sketch of existing power supply I 'think' (help us all) should work.

It's really hard to follow your terminology. What do you mean by "loop" ? There's two ways to connect multiple devices, but normally the one is PARALLEL (THEY ALL SHARE POWER & GROUND). The second way is SERIAL but that is more complicated because it depends on the voltages and nature of the devices and whether they have inputs and outputs so I don't want to get into that unless we have to.

sry for late response. thanx for reply.

by 'loop' I mean from one board to next - parallel wiring.

I am an electrician by trade for 20+ yrs and little knowledge of electronics but it seems to be pretty close to the same just different components and way lower voltages.

Ok, FYI, I'm an electronics tech (Engineering Tech) last 30 years and if it is easier for you, when you do a drawing , rather than having lines going diagonal , you can line up all the devices or subsystems and have all + lines run vertical and all - lines vertical but make the minus lines shorter than the + lines . Then run a pair of parallel lines horizontally that intersect with the vertical lines. At the point on the left of the page where the pair of parallel line begin, is the power supply powering everything. It looks cleaner.

well, i have the pwr_down working great. thanks so much for help.

dont know if i can post next question with this thread or new thread. issues is with same project but possible voltage drain???

is there a way to post .ino and eagle .sch files for somebody to look at and help me figure if i need to change/add certain small items? which section to post?

is there a way to post .ino and eagle .sch files for somebody to look at

Click on Additional options to add attachments.