projekte fachhochschule 	hamburg  E/I
3 Sharps an einem Eingang I tried not to let the size of the circuit board become larger than the 9V block-battery. Therefore the circuit board is divided into two parts, which are put together one above the other. Thus the entire circuit inclusive battery can be stored in a somewhat small box.
Platine von vorne The circuit consists of two circuits, which Michael Gasperi presents on his Lego page. One circuit is a multiplexer, which permits to switch several input signals to one signal. The other circuit, which is used here three times, is a small amplifier circuit . It permits to convert the input signal into a RCX readable signal.
If you place a passiv sensor (button) to an input at the RCX , there are approx. 5 Volt at this input. With an active sensor (light-sensor) there are somewhat more than 7 Volt. Using a light-sensor the RCX meassures in a "gap". That is, supply voltage is switched off for a very short time and the sensor value is read. So that in this short moment the voltage at the active sensor does not break down, the 22uF condenser is intended in the input, which keeps supply voltage in this "gap" upright. To be polarity safe the diode circuit is intended. The first two diodes (quite left) make ground potential available. The next two diodes make supply voltage available. Using the next two diodes the actual signal is meassured. The last two diodes are used to hold the Clock signal at HIGH level. If you switch this circuit from active to a passive sensor, the Clock signal goes briefly on LOW level. (the 0.1uF condenser and the 4.7kOhm resistance serve for the fact that this does not occur during the "gap".) The 4017 is a 10 channel decimal counter (CMOS). This IC switches from 0 to 1, then to 2, then to 3, then to 4 which triggers a RESET.
The IC 4066 contains four "bilateral switches". This achieved almost a switching attitude like a mechanical switch. With the outputs 0 to 3 the 4017 switches now successively the 4 switches contained in 4066. The first three switches are connected to the amplifier circuits of the three Sharps. The fourth input is connected to ground to get a starting point where the muliplexer circuit actually is. (output 4 from 4017 on HIGH passes the value 100 to the RCX.) This circuit could be extended to 10 analog signals. In addition you would have to designate six further bilateral switches (as well as six further amplifier circuits, if necessary). The RESET then is not executed by the 4th output anymore, but by the CARRY signal. The 10th switch would have to be put to ground then. The remainder of the circuit consists of a voltage regulation (7805 and 22uF condenser) that proces the 9Volt of the battery to 5Volt supply voltage for the 3 Sharps and of 3 amplifier circuits, which strengthen the input signals of the 3 Sharps. With use of the potentiometer in the amplifier circuits the degree of the reinforcement can be adjusted.
(I achieve values between 0 -> 10 cm and 80 -> 80cm in such way)
If you've got any questions please send me an email.