| Re: Störung auf linker radencoder: entwurfsfehler Kategorie: Pro-Bot128 (von Mansfeld - 23.03.2010 16:34) | ||
| Als Antwort auf Störung auf linker radencoder: entwurfsfehler von PepeV - 8.02.2010 22:22 | ||
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> The outputs of Timer T1 PWM X (X1_3 / OC1A and X1_2 / OC1B) couse interference on the collector > of the left wheel encoder phototransistor T3, which is connected to input port X1_9 / INT7. This is > coused by a design error on the printed circuit board of the drive unit. > > On the top side of that board the wire that runs from T3 to CON2 runs very close and parallel to the two > lines on the bottom side that carry the PWM signals for the motors. The result is that INT7 (left counter) > receives extra pulses from interference and the robot will not drive strait at low speeds. (At low speeds > the pulses from the phototransistors are less steep and therefore more sensitive to interference.) > > I solved the problem by disconnecting the printed wire from T3 to CON2 (cutting it near T3 and CON2) > and replacing it with a shielded wire. But hopefully the designers will find a more elegant solution by > altering the printed circuit board. Hi Pepe, thats a very interesting report. U. Sommer recommends in his book to insert two Schmitt-Triggers between collector of T3 / T4 and the Prozessor pins X1_9 and X1_10. How did you GND the shield: On both ends, sender end or receiver end? (I don't own a scope, I can't watch the result). Regards Fred | ||
Antwort schreiben Antworten:  Re: Störung auf linker radencoder: entwurfsfehler (von PepeV - 30.03.2010 10:12)Re: Störung auf linker radencoder: entwurfsfehler (von Mansfeld - 31.03.2010 15:51) | ||
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