Hello
I have an idea, and dont know for where to start.
Plan maybe try to use Hall Magnetic Sensor. Press button red led on and start counting for 60s. in this time frame you can turn it off by touching sensor. If not after 60s red led off and yellow is on. then you touch sensor yellow led off, green on and start timer for 5min. After that everything resets. green led off.
What kind of parts i need to use it for timer. The thing is that it should be small and easy put around your arm. Any ideas ?

 

Easily done with a pic, or other microcontroller, can be done with cmos CD4093 chips. Are you using touch sensitive sensors or skin resistance terminals on vero board.

 

thinking to use A1120 magnetic sensor. I think I need 2 A1120 one S polarity and N . For red and green led.I can program all on one CD4093 ? All is new to me so a lot need to learn and read.
Sorry for English its not my native

 

Cd4093 is not a microcontroller, its a cmos logic gate chip, do you prefer to use a microcontroller or logic gates and timer chips?

 

I have no idea. whats the easiest way ?

 

I would say the micro is easier, its the programme thats the part to solve, you have already started the logic steps, just need to make the delays, and input testing loops,which programming language do you know?

 

C++. I was thinking to use Genuino MICRO but is a little bit big. So maybe will try PICAXE-08M2.
What is better to use NFC chip or Hall magnetic sensors ?

 

Need to look at the datasheet of both sensors, and see which is best for your project, like sense distance, voltage, current drain..

 

The CD4521 is a 24-bit CMOS counter that will take a 32 kHz crystal and count all the way down to an 8 minute period. This should be enough to be the timebase for the state machine, with some decoding gates for the states.

ak

 

For us really old people, I would use 3- 555's & one OR, first as 60 s one shot, ( red), OS, second RS FF (yellow), & third 5 m OS, (green).
Sensor #1 resets #1 OS & #2 FF via. OR; sensor # 2 resets #2 FF via. OR, & sets # 3 OS...

 

I wouldn't use a 555 for a delay longer than a minute, better using a cd4060, or as said earlier a microcontroller.

 

Time tolerance not stated. 5 min for a 555 = no sweat, I run them up to 3 hours.