Basically this is a uni project (in product design) and i would like to make a "functioning" product for my 3rd year prototype.
I need to have a system where weight is recorded and sensed by the device, when weight is sensed the timer will start and then light up the product when a specified time is reached, obviously being a beginner and a student the cheapest and simplest solution is all i'm after.
i have looked at the teensy boards as i would need a micro usb port anyway, so a solution that works with this board would be great as well (if possible).
My lecturer said this would be extremely simple and would take him a week, however looking into it all i have no idea where to start...
thanks for reading.
where weight is recorded
What are the maximum and minimum weights? How accurate does the measurement need to be? How fast must the sensor respond (sample rate)?
How much light do you need? Light up a small area, a whole room? A few 5 to 8 mm LEDs can be powered by the Arduino. More will require more circuitry, depending on the use.
Google "arduino hacking scales" to see how some people use a cheap scales with Arduino.
Forget the 555. For the timing part look at the "blink without delay" example in the IDE (File, Examples, Digital) and this post.
I have never used Teensy, but I am sure that you can do your project with one.
The maximum weight would only need to be 0-2kg, nothing major, as far as accuracy goes, wouldn't need to be too accurate as it is only a rough model, but preferably be able to read a 5-10g weight change. And the lighting would just be a small strip of LED's, i will just adjust the amount to however much i need.
Thanks for the response
This hack might give some ideas on the scale.
great thanks, im thinking maybe get the (Arduino MICRO) as it seems to have more capabilities than the tweeny for basically the same price, buy some cheap scales and then the rest will be down to the coding basically right?
Well, you need to modify the scale, build or buy the amplifier, add in the bridge balance, wire it all up and calibrate the scale, too.
Once you have the scale working and calibrated, the rest should not be difficult.
You might look into force sensing resistors. They are easy to interface. They are not really meant for weighing but might be good enough once calibrated with known weights.. You could get one and see if it will work in your project.
thanks a lot for your advice, will order all the parts and hopefully be successful, the force sensor might be useful for the timer anyway right? because i would like to have the system so the led's light up after say 5 minutes for example, once the weight has been applied. Or would the load cell/amplifier be able to do that anyway?
Or would the load cell/amplifier be able to do that anyway?
Sure it could. You would set a threshold weight in your code and compare the current weight to that. If it is more, trigger the timer start and x time later turn on the LEDs. The problem with the threshold is that there is a minimum weight that will set it going, a lighter weight will not. Alternatively you could put the weight on and push a button to start or have an optical device (break beam or reflective) to sense the presence of the weight.
Yeah that will be fine, probably better for my project actually (the model anyway) with the minimum weight, because it will be for measuring how much water has been removed, so the minimum weight can be set for the weight of the empty bottle or cup so that it needs water or whatever in it to start the timer.