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@@ -95,6 +95,12 @@ Once the sensing unit is okay, try to find a good resistor value for the LEDs to
 Note that it is important to put a heatshrink around both the LEDs and the phototransistors to cut off parasitic lights.
 Moreover, with heatshrink it fits neatly into the eyesockets. When soldering the 2n3904, I recommend to solder first the center pin, and only then the side pins, otherwise it is too easy to create hard-to-remove solder bridges. Personally I find these little basterds harder to solder than the microcontroller itself (but I am bad at soldering!).
 
+If you do to not have an oscilloscope, that is okay, you can do it with a couple of debugging LEDs, check the blue LEDs on the following video:
+
+![](https://raw.githubusercontent.com/ssloy/penny/master/doc/proximity-sensor.gif)
+
+For a more distant obstacles the LEDs will be less bright.
+
 If you fail to assemble the proximity sensor, or simply dislike it, there are plenty of options:
 
 * You can use isf471 instead of the phototransistors and all the 2n3904 circuitry.