fischertechnik community forum

I had this problem in another fischertechnik set before, but the lens lamp is by far not strong enough to bridge the distance to the phototransistor on the other end. This seems to be a structural issue. I did some tests with values measured, and if the distance becomes more than 4-5 cm, the phototransistor doesn't measure anything anymore.

1. I have verified again and again that I'm using the lens lamp, not the LED lamps
2. This happened in another set too (bought years ago), with different lens lamps and different phototransistors

Can anyone confirm this? Any tips? The models in the Robotics set need to bridge distances of 10 cm if not more, and I seem to be very far away from that.

Hallo...
The LDR make no differents between sunlights or lamps.
There are two ways:
1. Take a tube on the LDR. There is a (ft part) black cap - and - a red tube.
2. You test the LDR only when the lamp is on. So if you frequently turn the lamp on and off, you can detect it.
Best regards
fishfriend
Holger Howey

Hi,

what type of input do you use? You have to configure the input as "digital", and RoboPro will just read 1 or 0. The phototransistor is not meant to read out analog values, i.e. voltage or resistance. It's just conductive or non-conductive depending on the light. And it works even for wider distances than 10 cm.

Kind regards,
Peter

Hello,

also, if the distance is large, you may need to adjust the position of the lamp so that it really targets the LDR. In the 1970s, the BS15 with round red nops were used to adjust the lamp in both directions (vertical to its beam).

Regards,
Stefan