Optical Flow Meter - A simple drop counter

This is a simple flow meter which is supposed to be used for measuring the flow rate of IV fluids in medicine. It is working as a special stopwatch. It is measuring the time that passes between two drops.

For measuring flow rate, you need to know how many drops make one ml (drop factor - gtts/ml). Then use this formula:

Volume (mL) Time (min)

x Drop Factor (gtts/mL)  =  Y (Flow Rate in gtts/min)

(http://www.dosagehelp.com/iv_rate_drop.html)

The flow meter is Arduino based. It has a Leonardo Pro Micro ATmega32U4 Arduino and an IR sensor. Every drop is been sensed as passes through the sensor's IR beam and starts a timer. You have only to choose the drops per ml. This number is known by the infusion device. Usually,  there are 20 large drops per ml or 60 small drops per ml.

The flow meter measures the drops per min then calculate ml per hour (the most common unit to measure flow rate in medical applications). It also, measure the total volume of fluids that passed from the start.

The device is not very accurate. Every drop has not exactly the same volume as the others. Also, it is sensitive to movements. I haven't tested it to tell how accurate it is, but in some applications, they claim that this method is 90% accurate (if there are no movements).

On the other hand, it is simple, has almost no moving parts and can be made very small. It doesn't  need consumables. Most important, it works without getting in touch with fluids.

The device's case was made of ABS plastic. The case was 3d printed. It is probably the most tricky part of this DIY. You have to make it flexible enough because there are many different sizes of infusion devices. Every infusion device has to be centred on the sensor.