about ultrasonic, I found them a bit pricy. there's some people who advised me to use a magnetic float sensor (low price) but I found some on digikey that have a higher price than they said.
I saw one in the lab and it outputs 4-20mA current which is an industry standard. Now, when I want to measure the level in PIC microcontroller, I should convert this current to a voltage for the sake of ADC.
What came on my mind is to use a current transformer because it's easy to use, it gives an output voltage that have a direct relation with the current.... (this can be further studied later as it's not very much precise).
SO, what's left to me is decide what float sensor to use.
the reason I want to avoid other types of sensors is the price. I want to make the device using cheap materials.
My project is like the following:
- a sensor to sense water level, with current transformer (or any other mean).
- PIC16F877A microcontroller.
- MOC3062M with BT139 TRIAC to control a single phase induction motor (for residential use).
- LCD to output some readings.
- few buttons to change some threshold values.
Threshold values: it's when the motor should start, say when water level is 50%, the motor should automatically start. when it's 95% it should stop... these are the thresholds ^_^. some buttons (or similar things) are used to adjust these as necessary.
Now, with that said, I think it's all clear what I wanna do. So, do you recommend a float magnetic sensor? If you recommend other types of float/level sensors it's OK to me, but the price should be cheap enough just like these magnetic ones.
Sorry for the long post... ^_____________^