Hey there,
I have a several enquiries to ask regarding my Arduino Project

But before that, I would like to explain what my project is about:

As you can see from the images,
I plan to make an automated timer system where

System 2 detects the tray placed on it through a switch, in which if the tray is placed on the sensor,
System 3's timer will start counting down. If it detects the tray for more than 3 hour 55 minutes it gives an audio cue, and then if it still isn't removed from the tray after more than 4 hours, there will be an audio cue. The timing of whenever the tray is placed on and removed from the switch is sent to the System 1.

Initial plan:
System 3 will be displaying the timer and displaying REMOVE if tray isn't removed after allocated time

New Plan:

System 3 will be an arduino connected to a timer bought from the market (NOT A MODULE),
as I believe that will save me time from trying to code the timer + display system. So whenever system 2 starts to detect timer, it will send that information through a NRF 24 L01 timer to System 3 and 4 hours of countdown will start commencing and also audio cue happening at 3hours 55 minutes and 4 hours respectively. What I also want to do is that System 1 will have a log of all the times tray was placed and the duration placed. Ideally, I want it to also highlight whenever time exceeded 3 hours and 55 minutes

Questions:

1. What kind of market available timers allow me to code it in such a way that I can integrate it with my arduino as mentioned in my new plan? Can you show me a few examples?
2. What sort of extra components should I purchase for my new plan?
3. What extra components should I buy to allow me to perform data logging?

Components list that I have right now:

1. 1 x Arduino Mega
2. 2 x Arduino Nano
3. 2 x 9V battery and Battery holder to connect to arduino to power it up
4. Momentary Switch
5. 3x NRF 24 L01 Transmitters
6. 1x MH Real Time Clock Module
7. LCD 2x16 Display (I dont plan to use this anymore if I can find a timer to use)

Your help would mean the world to me. Thank you so much!

Mod: Attachments deleted

 

Welcome to AAC.

Unfortunately, your description is very complicated and I suspect the project itself is not nearly so.

One thing I can help with is to suggest that your naive attempt to optimize by using some sort of standalone timer is almost certainly misguided. The functionality it appears you want is very easily provided by the MCU and RTC. The technique you would use is commonly called a state machine and there is an abundance of tutorial material concerning it on YouTube.

It is very unlikely that the code to use an external device would be materially simpler than using the state machine technique and the RTC. Writing to the display is also trivial. I think you should give the direct approach a try before deciding that a stand-alone device is a better idea.

As far as the nRF2401L modules are concerned, a salient question is the distance between ”systems” and the obstacles in the path. Depending on the version of the nRF24 modules you have, you could run into problems of range. The nRF2401L+PA+LNA with a good antenna can easily fix that, though.