Help design a IR button ?

Hi

Im building a scale with an arduino nano and the HX711 chip. Right now I have a simple push button for tare. But I've got some inspiration from an Ohaus scale. It uses an IR sensor to tare the scale. You just swipe your finger across the sensor and then it tare's.

Do anybody have an idea how to make same thing for an arduino? Not sure what kind of hardware I need to make it..

http://accuweigh.co.nz/wordpress/wp-content/uploads/2013/08/Ohaus-Navigator-NV.jpg

http://europe.ohaus.com/europe/en/home/products/product-families/NV-EU.aspx

Kind regards

Maybe an IR reflective sensor like the QRD1113?

Are you sure it’s not capacitive?

If my fat fingers can reflect the IR signal, the QRD1113 looks very nice :) ?

I have found a Sharp GP2Y0D805Z0F, but the range is a bit to long 0,5mm to 5 cm http://www.robotshop.com/eu/en/sharp-gp2y0d805z0f-ir-range-sensor.html

And a Phidget 1146, range 1-4 mm http://www.robotshop.com/eu/en/ir-reflective-sensor-1-4mm.html

Last but not least the TCRT5000L (Operating range: 0.2 mm to 15 mm) every cheap :)

http://www.robotshop.com/media/files/pdf/vishay-TCRT5000L-infrared-reflector-specs.pdf http://www.ebay.com/itm/10Pcs-TCRT5000L-TCRT5000-Reflective-Optical-Sensor-Infrared-IR-Switch-infrared-W-/221515042913?hash=item3393535061

Not sure if any of these will work in my setup?