I want to build a weight sensor for my kid's car seat. I want that sensor to make a call a few minutes after I'm shutting down my car, conditioned to my kid still sitting on the seat.
First of all, for mechanism itself (before connecting to the car), is there anything I need which is not in this list:
Arduino
SIM900 GSM model
Load cell + HX711
Now, I know the SIM900 input voltage can be 3.7~5.0 or something like this. How should I connect the whole thing to the car and avoid voltage problems?
You would think that it can't happen, but it does some 50 times a year in the U.S.
The Adruinos have a voltage regulator built-in that should provide the +V your GSM and Load Cell need.
Go ahead and buy the parts and experiment with them on the bench one at a time. Then we can help you make one sketch to rule them all.
Our kids grew up before Arduino and cell phones, else I would have done the same thing. My wife always attached her purse to the belt on the car seat. She couldn't go into the office without her purse and the employee keycard inside.
I don’t think you need a load cell. You don’t need to weigh the child. You just need a basic switch contact that requires any significant weight to activate. These are already used in ride on lawnmowers, car seats etc. No need to over complicate it. Then the programming is simple: if car ignition off and switch still closed sound alarm.
Thank you (or part of you ) for your answers. I'm not worried about the programming part but the components I need. Don't I need anything else except what I've mentioned? I'm purchasing the parts online and it will take some time until I get them so I want to miss nothing.
Not sure how we could know what parts you need if we don’t know what you are going to do with them. Each of those parts will do what it says in their data sheets. However, if you use them in different ways you may need additional parts. Generally that is why you prototype concepts. Do you have a wiring diagram? It should contain all the parts you need.
Plan on paper
Then prototype on breadboard
Then consider real world
That will save you money and time dismantling car seats.
By the way. You can get off the shelf car seat occupancy detectors that wire directly to the cars electronics then all you need to do is wire a buzzer for when you turn ignition off.
liorhen9:
I want to build a weight sensor for my kid's car seat. I want that sensor to make a call a few minutes after I'm shutting down my car, conditioned to my kid still sitting on the seat.
Suppose you build this and suppose it works as expected for a period of time.
Then what happens on the day when it does not work.?
It's a sad fact of life that stuff fails and DIY stuff is more likely to fail than a commercially engineered and tested product.
pmagowan:
Not sure how we could know what parts you need if we don’t know what you are going to do with them. Each of those parts will do what it says in their data sheets. However, if you use them in different ways you may need additional parts. Generally that is why you prototype concepts. Do you have a wiring diagram? It should contain all the parts you need.
Plan on paper
Then prototype on breadboard
Then consider real world
That will save you money and time dismantling car seats.
By the way. You can get off the shelf car seat occupancy detectors that wire directly to the cars electronics then all you need to do is wire a buzzer for when you turn ignition off.
Thank you for your answers, I read it quietly. I'm pretty sure my best practice right now is to use the load cell+HX711+GSM Module. I just want to know if I must have another component for that thing to be working.
Thanks again.
Robin2:
Suppose you build this and suppose it works as expected for a period of time.
Then what happens on the day when it does not work.?
It's a sad fact of life that stuff fails and DIY stuff is more likely to fail than a commercially engineered and tested product.
...R
You're pretty right but let's keep this discussion for another time
) for your answers. I'm not worried about the programming part but the components I need. Don't I need anything else except what I've mentioned? I'm purchasing the parts online and it will take some time until I get them so I want to miss nothing.