6.3 Elements introduction
As for the element, here, it is the nixietube. If we know the principle of nixietube, then the experiment is relative simple. In the next sections, we will focus on the principle of nixie tube.
By the segments, the nixie tube can be divided into seven segments display and eight segments display. And the former is more than one a unite of LED than the latter, i.e., the display of decimal point.
According to the display number of “eight”, it can be divided into one, two, four digital nixietube, and so on, which as shown in 6-1.
Figure 6-1 Classifications of nixie tube
By following the connection of LED, the nixie tube has two types: a common anode and a common cathode. The anode tube means that all of the anodes of LED in nixiebue are connected together to a point, as shown in Figure 6-2(c). If the common anode is connected to a 5V power, the corresponding segment would lighten, when the other end for some segment is low voltage level. But, its cathode is a high level, the corresponding segment would not lighten. The common cathode is that all of the cathodes of segments are connected to a COM port, which is a GND, then, if the other end is connected to a high voltage level, the number segment would be lightened, as shown in Figure 6-2. But if the other end is low, it cannot lighten.
(a) shape and pin (b) common cathodes (c) common anodes
Figure 6-2 Shape and structure of nixietube
Principle of nixietube
As stated in the above, each segment is composed of LED. Then, in use, it is the same as LED. A current-limited resistor must be connected additionally to avoid damaging LED. If the common polarity and each pin are right for the positive and negative, the corresponding segment switches into conduction. From Figure 6-2(a), we can get different digital number by the different connection of pins. On the contrary, if the polarity is not right, the segment cannot be conducted. Therefore, if we want to get the designed digital number, two key problems must be solved, i.e., the polarity and the order of pins.