Kommentar: Einfügen von HTML im Kommentar: Link einfügen: <a href="LINKURL" target="_blank">LINKTITEL</a> Bild einfügen: <img src="BILDURL"> Text formatieren: <b>fetter Text</b> <i>kursiver Text</i> <u>unterstrichener Text</u> Kombinationen sind auch möglich z.B.: <b><i>fetter & kursiver Text</i></b> C Quellcode formatieren: <code>Quellcode</code> BASIC Quellcode formatieren: <basic>Quellcode</basic> (Innerhalb eines Quellcodeabschnitts ist kein html möglich.) Wichtig: Bitte mache Zeilenumbrüche, bevor Du am rechten Rand des Eingabefeldes ankommst ! -> I > Hi all, > > The wheel encoders are a weak spot of the otherwise wonderfull design of the Pro-bot128. They easily > pick up noise like interference from lights in the surroundings or electric interference (cross talk) from > signals that drive the motors of the bot (as I wrote earlier on this forum). Tuning the position of the > phototransistors and the IR-diodes as suggested in the manual is useless. At least I did not notice any > improvement. I would like to share here some better tips to improve the reliability of the wheel encoders. > > Key point is that the slopes of the pulses from the phototransistors should be as steep as possible. The > steeper they are, the less time is spent near the thresholt value of the input port of the Mega128 and the > less time there is for interference signals to create extra thresholt crossings. There are two ways to > improve the steepness of the slopes of the pulses. > > 1. Increase the difference between the reflection of the dark and the light segments on the encoder > gear wheel. I used aluminium foil and printer blackend paper. This is how. > Take a sheet of ordinary paper. Glue aluminium foil onto it with the shiny side on top. > With a drawing program draw a circle with eight black and white segments like the plastic sticker > that came with the bot. Also draw a white inner circle where the axis will come. Make two copies, > for each gear wheel one. Print them. > Cut out the circles. Cut out the white segments but leave the inner circles intact to keep the black > segments attached. > Glue the resulting four leaf clovers on the paper/aluminium sheet you prepared earlier. > Cut out the circles and cut out the inner circles for the axes to obtain the improved stickers for the > encoder gear wheel. > > 2. Decrease the distance between the encoder gear wheel and the phototransistor and the IR-diode. > There is a lot of blacklash (space) between the encoder gear wheel and the phototransistor > and the IR-diode. This can be deminished by clamping a washer on the end of the axis of the gear > wheel. Take an ordinary steel washer with a hole that is slightly to small and file it out until it fits > securely on the end of the axis. Leave just a little space for the gear wheel to run smoothly. > A retaining ring will do the same job but might be more difficult to obtain. > This will make the wheels run smoother and with less noise too. > > Regards, > Pepe
