Category Archives: Experiments

Fans and Inductive Loads

Inductive kickback sounds scary so I have been trying to and possibly failing to  understand the theory behind it and how to counter it. I have at least done my best to prevent the Micronel Centrifugal Fan I have been using for my table tennis project from frying my relays by adding a kickback diode. Initially the wiring threw me for a loop until I found that for some odd reason the red cable is negative and black positive. Luckily nothing got fried in the process. Measuring the voltage spikes before I added the diode and after shows a definitive difference. There is no measurable voltage spike with the diode attached. Fingers crossed that I got this right.

Testing Infrared Emitters and Detectors

I am trying to detect a table tennis ball passing trough a polypropylene pipe. (Don’t ask why just yet. It’s a secret.) The ball is propelled trough the pipe by air pressure from a centrifugal fan. I have been using a Sharp Infrared Proximity Sensor for this but it has several drawbacks:

  • The hole needed in the pipe is quite big, approximately 10 by 40mm. This leads to a loss of air pressure and the ball moves slower.
  • The sensing range of the sensor is 30 to 400mm so the bracket for holding the sensor needs to be quite big since the sensor needs to be mounted at least 30mm from the pipe.
  • The ball moves so fast trough the pipe that the sensor is not fast or accurate enough to detect the ball passing. The ball is detected but the sensor reading is not high enough to rule out any errors .

Continue reading Testing Infrared Emitters and Detectors

Electronics for current project assembled

This is the prototype for a project I am working on at the moment. The project involves sensing a table tennis ball and reacting to its position. The components from top left: Phidget Motor Controller, Firgelli L16 Micro Linear Actuator 1:30, 3x Sharp Infrared Proximity Sensors, Phidget Interface Kit 8/8/8 with a Phidget Dual Relay Board wich in turn will be connected to a 12V Micronel Centrifugal fan.

The final project will look nothing like this but having the components mounted to a piece of chipboard makes it easier to keep all the parts from becoming an even worse jumbled mess while I write the code.

Now I better start writing the Air app to control it.