Ready to benchmark!

The RC brushless motor test bench (version 1) is ready.

The RPM sensor is made with an infrared LED and an infrared phototransistor (TCRT5000L). The IR LED constantly emits an IR light that is invisible to the eye. the phototransistor acts as a switch that is toggled by IR light. Every time a prop blade is between IR led and IR phototransistor the IR phototransistor switches off. In most RPM tutorials this on/off switching is counted during some time. e.g. 100 times a switch off during 250ms equals to 12000 rpm for a 2 bladed prop. But this means you'll only have an RPM readout every 250ms this would slow down my benchmarking.
To calculate the RPM I use the time difference between the switches, or the time difference between the blades. This gives me a RPM readout every turn of the prop. e.g. 4 miliseconds time difference between the blades equals to 7500 rpm for a 2 bladed prop.

Now I have all sensor data for this project. And I can start benchmarking my motors and props. The current PC application is a bit limited. It just start/stops a benchmark cycle and it captures all data. The data can be saved to a file or copied to clipboard. At the moment there is no fancy graph. But this can be done with any spreadsheet application because the saved benchmark file is a tab delimited csv file that can be imported in almost all spreadsheet applications.

RC Brushless motor test bench

My RC brushless motor test bench project is almost finished. I hooked up an ACS 712 30 ampere current sensor. This sensor will read out the current consumption of the motor and send it to the arduino board. I also made a basic voltage divider in order to read out the battery voltage with the arduino board.

I currently have programmed the arduino board to read voltage, current and thrust. With a very basic command set and human readable output it is possible to control the arduino (test bench) completely by hand with arduino IDE serial monitor feature.

But I also created a small PC application that makes it easier to control to board and run a pre programmed benchmark sequence. With this small program it is possible to save or copy the incoming data. This application is created with the processing IDE and is java based. So it should run on every java compatible platform (operating system)

The ACS 712 sensor is a cheap one from ebay. In order to get it to
work well you should add a capacitor on the ACS 712 FILTER pin. To achieve this you will need some soldering skills. Without the capacitor this sensor is useless in this application. I used a 10nf cap.

Next step is to integrate a RPM counter.