I have developed a generic "voltage switch" board that can select one of two circuits based on whether an input voltage is higher than a reference voltage. If the input voltage is lower than the reference voltage, circuit one is enabled; if it is higher, circuit two is enabled. This is going to prove extremely useful in the long run. You can use it to turn anything you want on or off based on a signal from any sensor. I am going to use two of them for this project: one for the MAF sensor and one for the ACT sensor. When the input voltage from both sensors are higher than their respective reference voltages, the water pump will be turned on. I'll probably use another one to monitor the water level and turn on a LED when it is almost empty.
primarily, a potentiometer and an op-amp used as a comparator. then there is a transistor and a relay thrown in for good measure ...
Almost there. Here's the latest schematic ... It has hysteresis now, which means that the circuit can be turned on at one voltage and off at another voltage. For example, it could be turned on at 190* and off at 170*. I'm working on the prototype board now. I found a place that will make me 3 printed circuit boards for $51. here's what the board will look like ... These things are going to come in really handy for later projects ...
Ha, magnetic circuit terms applied to solid state electronics. Got a picture of a hysterisis curve? Part of my training in the Navy was on magnetic amplifiers. Bet nobody knows what that is...........OLD technology!
