and the positions of the individual spectra lines (see Figure 12). This facilitates the grading of the project. An additional subroutine allows the input of molecular constants that can then be used to generate simulated spectra of actual molecules, or may he used by the students to compare the spectrum generated by their answers with the assigned spectrum. The program is written in Graphic Systems Basic for execution on a Tektronix 4051 with a Tektronix 4662 digital plotter. I t consists of 232 lines including 20 remark statements and requires 16K of $-hit words. Documentation includes a copy of the listing, an example of the output, references for the equations used to generate the spectrum, and a brief description of Tektronix Graphic Systems Basic to assist conversion to other graphic systems. This documentation package is available from the author upon request. Please include a self-addressed, stamped, legal-sized envelope. Send correspondence to Dr. Michael B. Moeller, Department of Chemistry, University of North Alabama, Florence. AL 35632. Figure 14. Schematic of SmartChatis AID board
20 spectra. check or purchase order should he made to ~ e partment of Chemistry, UNA.
SmartChart: An Inexpensive Chart Recorder for the Freshman Laboratory William E d w a r d T i t m a n a n d T o m L y o n s Fisher Junlata College. Huntingdon, PA 16652
Until recently, the lahoratory chart recorder has been the primary means of collecting instrumental results. The computer, however, is rapidly replacing the classical chart recorder in most lahoratory applications; the computer is more reliable, faster, "smarter", and doesn't run out of paper or ink. Employing computerized instrumentation in the freshman chemistry lahoratory is clearly desirable if that course is to he truly modern, but until now computers have been too expensive to permit modernization of the introductory lahoratory course. The recent introduction of the Sinclair ZX81 microcomputer has dramatically and favorably altered the economics of computerization. The Kit Form of the ZX81 costs $80 and includes a keyboard, an 8 K BASIC interpreter, 1K of RAM, a power supply, and a T V converter. An inexpensiveTV ($70) and tape recorder ($45) are required to make the system operational. (One tape recorder is sufficient for several ZXBls
in most applications.) Expansion of the memory to 4 K and addition of the 8 bit analog-to-digital ("AID") converter described in this article transforms the ZX81 into an "intelligent" chart recorder dubbed SmartChart, which can he assembled for half the cost of a traditional chart recorder. Thus. i t is now feasible to computerize every instrument in the freshman lahoratory. SmartChart consists of three assemblies: the ZX81 computer, the Sabre Systems SS-02 Multi-purpose Memory Board, and the AID hoard (Fig. 13). All of the parts required for both the expansion of memory to 4 K and the addition of the AID converter are listed in Table 1. The schematic diagram (Fig. 14) shows only the wiring of the AID converter,
Table
1. Parts List for S m a r t c h a r t '
Memory Board SS-02 Muiti-purpose Memory Board (Sabre Systems. 1415 Creek Hollow, Seabrook, TX 77586) TWO61 16 2 K RAMS Two 24 p n so denall s o c e s 74-5138 3-108- one decoder 16 p ~ soldertail n socket Two 1N914 diodes TWO3 9 K resistors AID Board
Figure 13. SmartChan hardware The AID board is to the iefl and the Sabre Systems 89-02 Multi-purpose Memory Board, containing two 61 16 2K RAMS, is to 4 right. The Zero Insellion Force socket will Lx: corlfigwedb, accamnadate a 2716 EPROM in the near future. The plastic enclosure was lined with metallic tape to reduce radio frequency interference.
570
Journal of Chemical Education
2% X 3% in. grid board (Radio Shack) 9 V banery eiiminator National Semiconductor ADC808 AID convener 28 pin wire-wrap socket 4049 hex invetting buffer 16 pin wire-wrap socket 4001 quad 2-input NOR gate 723 voltage regulator Two 14 pin wire-wrap sockets R1. R3 = 10 K resistors R2 = 100 K resistor R4 = 1 K resistor R5 = 47 ohm resistor R6 = 2.2 K resistor R7 = 10 K screwdriver potentiometer (Setto about 5.9 K to obtain a 5 V output from the voltage regulator.) C1 = 0.1 UF Capacitor C2. C4 = 100 pF capacitors CS = 0.01 UF capacitor
mese p a i s can be puclwBd from a mall order eacbonics suppller (except where mtedl for about $70
Despite its limitations, SmartChart is a practical alternative to traditional chart recorders in the freshman laboratory and in other situations where expense is the mimarv consideration (Fig. 15). We thank William M. Blazina, Jr. for assemhline the
Personal Literature Retrieval System Harry E. Ensley Tulane University. New Orleans, LA 701 18
Figwe 15. Smartchart interfaced to a gas chromatograph.
inasmuch as the instructions for the SS-02 are provided with the hoard. In addition to the tools found in any toolkit, a 25-W soldering iron and a wire-wrap tool are required. The major chip on the AID board is the ADC808, an 8 hit A D converter that has an input voltage ranee - of 0 to 5 V and a conversion time of approximately 0.5 milliseconds. The ADC808 is supported hv three additional chips on the AID board: 1) he-723 voliage regulator suppli& a reference voltage to the AID as well as the power for all of the chips on the hoard, 2) the 4001 quad NOR gate provides hus decoding, 3) the 4049 hex inverter forms a 135 kHz clock that synchronizes the digital circuitry of the ADC808. The ADC808 is mapped into a 2 Ii block of memory a t decimal addresses 30720 through 32767 (nominally 310001, rather than a single address. This approach greatly simplifies the address decoding hardware since the SS-02 Memory Board already decodes to the 2 K level by detecting when lines A l l through A14 are low. Only two other bus lines are monitored by the A D : The ZX81 WR line (activated by a POKE) hegins the conversion of the analog voltage from the instrument to a binary numher, and the bus RD line (activated by a PEEK) makes the numher availahle to the BASIC program. Thus, for example, the sequence: 230 POKE 31000,l 240 X = PEEK(31000)
stores the results of an AID conversion in the variable X, where X is an integer from 0 to 255. Notice that SmartChart is controlled entirely by BASIC statements. Since BASIC is now taught in most high schools, students should he able to write their own routines for SmartChart. provide such a high voltage. Therefore, iiis desirable to utilize a software techniaue known as time-summina to simulate data point. This technique is easily incorporated-into B A S ~ C oroarams that employ SmartChart: amplification factors as high as 20 are fea[ible. Obviously, a $250 chart recorder will have some limitations. A major one is poor graphics resolution, which is only 44 pixels high and 64 pixels wide. However, numbers acquired from the AID have a precision of 1 part in 256 or about 0.490, so that calculated results are much more precise than the plot suggests. Thus, the plot should be used to discover gross ah'. normalities in the experiment while the numerical results should he used to determine nrecise values. Another problem is the lack of a real-time clock. The PAUSE statemedt can be used to set the interval between A D inputs, hut this approach .. assumes that the plot calculations require either negligible or const,ant time.
Numerous methods have been developed to allow researchers to maintain and search records of useful references. The most common method, that of knitting needles and punched index cards, works quite well as long as the numher of cards remains relatively small (500-2000); however, crossreferencing problems soon become insurmountable. At the other end of the literature retrieval spectrum are the numerous on-line searches that are available. Using these searches can sometimes create difficultiessince theresearcher'sinterest in a particular paper may not have been included in the abstractor's keyword survey. The widespread availabilitv of relativelv inexnensive microcomputer; offers a potential solution tothis problem (33). The program LIT SEARCH, described here, is an attempt to fill the gap between index card filling systems and on-line literature searches. It is particularlv attractive since the keywords are chosen based on the researcher's particular interest and in hislher own jargon. LIT SEARCH is a menu driven program and requires no previous computer experience to either enter data or perform searches. (A standardized article summary form can he used by the researcher while reading the literature thus allowing data entry to he performed later by a nonscientist.) Menu 1 allows six choices: 1) Enter Datasets, 2) Perform Display Search, 3) Perform Printer Search, 4) Review Datafiles, 5 ) Perform Datafile Maintenance, or 6) Exit. The first five choices of Menu 1 transfer the operator to one of five submenus to further define the desired operation. The Enter Dataset n~oduleallows the user to start a new literature file (including the creation and formatting of the required files) or to add datasets to an existing file. Searches can he performed on the monitor (or printer, if availahle) using an author. a kevword. an author-kevword combination. or two keywordsas the search key. A typical keyword or author search through a thousand articles requires 2 to 3 seconds. In order to expedite searches, each word in the dictionary is assigned an address using a hashing function (34), which calculates the address rather than searching for the word in an ordered list. The Review Datafile module reports the numher of journals, authors, articles, and keywords that have been entered. The Datafile maintenance module allows keywords to be deleted from the dictionary or the spelling of a keyword to be changed or corrected. It also allows the user to obtain a printout of all or part of the information entered to check the accuracy of dais entry. Currently, LIT SEARCH is designed for use with a 48K Apple II/lI+ with two Disk I1 drives, with or without a Silentype printer. Using this system, the Article File is stored on drive 1 and the Keyword File is stored on drive 2. This twodiskette volume is capable of storing up to 1000 articles that have up to 18 keyword descriptors per article. When the volume is full, another two-diskette volume is initialized and data entrv can he continued on the second volume. A listine of the 329-statement Applesoft Basic program with separate proeram descri~tionis availahle for $5 ($20 on a 16 sector diskette). The check or money order should he made payable to the author. Volume GO
Number 7
July 1983
571
