I want to make timer with a 7-segment display that shows how much time (in hours and minutes) has passed since the reset button was pressed.
I want it to consume very little power, so that it will last as many days as possible on a tiny battery, with a low voltage (like 3 volts). I want the circuit to be small, so it shouldn't take too many components, especially big ones.

I don't have much experience with digital circuits. However, I have small amount of experience programming the Arduino Uno. But I won't use an Arduino Uno for this, as it's too big and valuable for this.

What IC's should I use to build this?

 

(At least) Four LED digits are going to drain a tiny battery fairly quickly unless they are very small digits. You could use LCD instead. That's a lot less current but more complicated to drive.

 

If you look though this youtube search (the search is "how to save power arduino"), I looks like there are some great videos on power saving.
A.H.W.

 

I believe there is no one IC that will do that.
It seems like a lot of work to build something that's so easy to buy already built as a kitchen timer.

 

I want to make timer with a 7-segment display that shows how much time (in hours and minutes) has passed since the reset button was pressed.
I want it to consume very little power, so that it will last as many days as possible on a tiny battery, with a low voltage (like 3 volts). I want the circuit to be small, so it shouldn't take too many components, especially big ones.

I don't have much experience with digital circuits. However, I have small amount of experience programming the Arduino Uno. But I won't use an Arduino Uno for this, as it's too big and valuable for this.

What IC's should I use to build this?

The LED displays consume a huge chunk of your power. Do you need them on all the time or just to show the current clock value when a button is pressed (either the same or different than clock reset button).

 

Forget it mate,!!!! you won't make for less than you can buy it, ask yourself which battery you want, then how much current it can supply, that will give you the maximum length of time it will run for, leds take far more current than a Lcd display. Get on Ebay, Amazon...

 

Perhaps a real time clock circuit?

 

Why not just a cheap stopwatch? Remove the case to shrink the size.
https://www.amazon.com/gp/product/B...289a-5d35-bd86-6255c58c48a1&pf_rd_i=698866011
https://www.amazon.com/gp/product/B...289a-5d35-bd86-6255c58c48a1&pf_rd_i=698866011
Ken

 

Taking a stopwatch and removing the case won't work. I need to be able to supply an external reset signal.
To reduce the power, I could use an LCD 7-segment display, or I could use an LED display that is only turned on while holding down a button.

Isn't there any kind of IC that can count upwards starting from 0 until reset, and another IC that can output this data to a 7-segment display?

 

Maybe you can buy a small lcd timer and choose the count up function, you also need to connect two keys as Start/Stop and Clear(reset) from inside, and using two transistors to replace them, plus one Gnd wire, the two transistors as two switches, when you want to do the Clear(Reset) then you need to send two signals begin with Start/Stop key and the following is Clear(reset), and then the display will be clear to 0:00 00, but this timer only can be count up to 9:59 59, 9 hours, 59 minutes, 59 seconds.

 

What is the max. number of hours?
What happens if the counter exceeds that number; stop or roll over and keep going?

ak

 

Taking a stopwatch and removing the case won't work. I need to be able to supply an external reset signal.
To reduce the power, I could use an LCD 7-segment display, or I could use an LED display that is only turned on while holding down a button.

Isn't there any kind of IC that can count upwards starting from 0 until reset, and another IC that can output this data to a 7-segment display?

Just some random thoughts.

With regard to your last question above: No, not in hours and minutes.

You might get away with a microcontroller and an LCD display. One IC, handful of external components and a display module.

Why wouldn't a stopwatch work? I'm sure it has a reset button. Simply extend it to an external location, perhaps as simple as a pair of wires.

Arduinos are too big? You do know there are different varieties? Nano. Trinket. Others...