![]() The same technique anchors the Arduino board.Īt first I worked up the circuit on a solderless bread board using code from the Adafruit web site. I use “L” shaped bits cut from a paper clip, soldered to the board ground, and to the ground plane. In this photo you can see the interface board soldered down near the front of the Altoids tin. It’s a bad thing to overvolt an Arduino pin, please Don’t Ask Me How I Know This. A series resistor and zener diode make sure the voltage ratings of the Arduino input pin are not exceeded. The series resistor value is low enough that the power feed is still adequate for the small plastic sensor, so the option jumper just selects where to pick off the pulse signal. The positive supply feeds through a resistor which produces enough voltage drop when the large sensor is pulsing to trigger a digital low at the Arduino. I constructed the interface circuit on a small piece of project board from Radio Shack (RIP). I designed an interface circuit that works with either unit by changing an option jumper. ![]() The display must sense a pulse by looking for an increase in supply current. ![]() It signals a pulse by shunting power to ground through a low resistance. The electrical interface on the small flow meter has 3 wires, power, ground, and pulse output – relatively simple to connect to the microcontroller. Flow Sensor Prototype with Large Flow Sensor ![]()
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