PsL Monthly 1993 December

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Text File | 1991-12-27 | 12.1 KB | 208 lines

Digitized Voice Programmer's Toolkit for the PC ----------------------------------------------- Version 2.0 Copyright (c) 1988,1989,1990,1991 Farpoint Software Construction Notes for the Voice Digitizer ------------------------------------------------------------------------------ This document assumes that you are building the digitizer by hand from the schematic. It will supply details of the circuit that may not be apparent from the schematic. It will also recommend certain construction and operation practices for best results. Some portions of this file are duplicated in the file VOICEKIT.DOC. Here is a parts list: | Estim. | Estim.| |Sgl. Unit| Net | Quan | Cost | Cost | Type | Description Ref. Des. ======================================================================== 1 .75 .75 MINI PHONO JACK J1 1 1.00 1.00 SMALL 3-TERMINAL BLOCK J2 1 2.50 2.50 DB25 FEMALE RIGHT ANGLE J3 P.C. BOARD MOUNT CONN. 1 .25 .25 MOMENTARY (N.O.) S1 PUSHBUTTON SWITCH 1 1.50 1.50 DPDT SWITCH S2 1 1.00 1.00 LF347N QUAD OPAMP U1 1 .50 .50 LM1458N DUAL OPAMP U2 1 .50 .50 MC1488P RS232 DRIVER U3 1 .75 .75 CD4019BE QUAD AND/OR SEL U4 1 3.50 3.50 LF398N S/H AMPLIFIER U5 1 6.00 6.00 ADC0841CCN A/D CONVERTER U6 1 .75 .75 MC1489A RS232 RECEIVER U8 1 .75 .75 LM78L05ACZ 5-VOLT REGULATOR U9 6 .25 1.50 1N4148 SIGNAL DIODE D1,D2,D3, D4,D5,D6 1 .25 .25 RED LED D7 1 .25 .25 GREEN LED D8 1 .50 .50 100K TRIMPOT R8 1 .50 .50 200k TRIMPOT R24 2 .25 .50 .0022UF POLYESTER CAP C8,C9 2 .25 .50 .0039UF POLYESTER CAP C6,C7 12 .25 3.00 .1UF CERAMIC CAP BP2,BP4,BP6, BP8,BP10,BP12, BP13,BP14,BP15, BP16,C3,C15 1 .50 .50 .33UF POLYESTER CAP C14 2 .75 1.50 1UF POLYESTER CAP C4,C5 2 .10 .20 100PF CERAMIC CAP C1,C2 1 .75 .75 100PF MICA CAP C12 4 .75 3.00 10UF TANTALUM CAP C10,C11,C13,C16 8 1.00 8.00 22UF TANTALUM CAP BP1,BP3,BP5, BP7,BP9,BP11, BP17,BP18 2 .15 .30 1K .25W METAL FILM RES. R5,R6 2 .06 .12 2.2K .25W CARBON RES. R17,R19 1 .06 .06 3.3K .25W CARBON RES. R15 2 .06 .12 10K .25W CARBON RES. R10,R22 4 .06 .24 12K .25W CARBON RES. R11,R12,R13,R14 1 .06 .06 22K .25W CARBON RES. R7 2 .06 .12 33K .25W CARBON RES. R2,R20 2 .06 .12 39K .25W CARBON RES. R1,R3 1 .06 .06 68K .25W CARBON RES. R4 2 .06 .12 100K .25W CARBON RES. R18,R23 1 .06 .06 220 OHM .25W CARBON RES. R21 2 .06 .12 27 OHM .25W CARBON RES. R25,R26 The costs in this list are ONLY ESTIMATES, based on rounded averages of prices from several sources. Note that this document was written in December 1991, and that prices will change over time. Parts cost may vary widely, depending on the vendor, so consider shopping around. This parts list includes only the actual circuit components. You will also need a prototype board, a soldering iron, solder, chip sockets if desired, wire-wrap sockets and tools if wire- wrap techniques are to be used, and whatever screws and other hardware might be needed if you intend to mount the device in an enclosure. In addition, you will need two 9-volt batteries or a split power supply, a microphone, and a full DB-25 "straight through" cable. There are two locations in the schematic where redundant components are shown in order to increase versatility or availability: (1) Use EITHER R9 and R16 OR trimpot R24, but not both; R24 is recommended. (2) Use EITHER U4 OR U7, but not both; selection depends on availability. The power supply pins for several of the integrated circuits are not shown on the schematic in order to reduce clutter. This is a list of all the integrated circuits, their package pin counts, and their power supply and ground pins. In some cases, the power supply pins may already be shown on the schematic. Ref. Des. Part Type Pin Count Ground +5 +9 -9 --------- --------- --------- ------ ---- ----- ----- U1 LM348N 14 -- -- 4 11 U2 LM1458N 8 -- -- 8 4 U3 MC1488P 14 7 -- 14 1 U4 CD4019BE 16 8 16 -- -- U5 LF398N 8 -- -- 1 4 U6 ADC0841CCN 20 10 20 -- -- U8 MC1489A 14 7 14 -- -- All the capacitors shown in parallel groups in the lower left area of the schematic are power supply bypass capacitors. Their purpose is to provide each IC with isolation from the noise induced on the power supply rails by the other parts of the circuit. These capacitors should be distributed around the board so that each power supply pin of each IC is connected directly to a bypass capacitor or a pair of bypass capacitors whose other terminal is solidly connected to ground. Components U1, U2, and U5 should have two bypass capacitors per power supply pin: one 0.1 uF and one 22 uF tantalum. This is a list of which bypass capacitors are to be associated with (connected to the power supply pins of) each IC: IC Ref. Des. Bypass Cap Ref Des. ----------- ------------------- U1 BP1, BP2, BP7, BP8 U2 BP3, BP4, BP9, BP10 U3 BP17, BP18 U4 BP13 U5 BP5, BP6, BP11, BP12 U6 BP14 U8 BP15 Capacitor BP16 would theoretically be associated with U7 if used instead of U4. Connect capacitors C11 and C13 near the power switch. C14, C15, and C16 should be connected directly to the leads of regulator U9. Note that the power pins of U3 are not connected directly to the supply, but draw their power through R25 and R26 in order to reduce U3's contribution to power supply noise. In some cases, depending on the exact board layout, the presence or absence of a ground plane, and the relative noise level and proximity of the power source, is may be possible to eliminate some of the bypass capacitors without any noticeable effect. However, since the factors influencing this are difficult to calculate, we suggest that you use all of the bypasses shown when the project is initially constructed. Extra unneeded bypass capacitors cause no harm, but missing bypasses, in spots where they are needed, can functionally disable the device. If a pin on a part is shown connected to nothing, and furthermore if it shows no "netname" label (pin numbers don't count), then it should in fact be left unconnected. Some points in the schematic should be connected together even though there are no lines joining them. This follows the "netname" convention. Any two points (wires) on the schematic which possess identical net name labels are actually interconnected. For example, there are four places showing the label "VREF". These should all be connected together. If possible, use a prototype board which has a "ground plane". This is a continuous metal sheet covering the entire board except for clearances to allow pins to pass through holes. If your prototype board has a ground plane, then every pin which requires a ground connection should be connected directly to the metal ground sheet at the location of the pin. Try to position the parts on the board to minimize the length of the interconnecting wires between the parts. Keep all wires as short and direct as possible. Once all components are wired into the circuit, inspect the unit carefully, noting in particular that all diodes and polarized capacitors are oriented correctly. If you used sockets (strongly recommended), remove all ICs from their sockets. Leave U9 in place, even if it is socketed. Apply power to the unit, being VERY careful not to connect it backwards. Turn on the power switch and use a voltmeter to measure the voltages (relative to ground) on each power supply pin of each empty socket, as shown in the table of power supply pins above. If your supply is, for example, (+) and (-) 12 volts instead of 9 volts, then 12 volts should be substituted for 9 in the table. The pins that are specified as being +5 volt pins are driven by linear regulator U9, and should read between +4.8 and +5.2 volts as long as the incoming positive supply is +7.5 volts or higher. Any pin which shows an incorrect voltage is almost certainly an indication of a wiring error. After all power supply pins have been verified, disconnect the supply and install all the ICs into their sockets, being careful to observe the proper orientation. Reconnect the supply (with the power switch off), plug in a microphone, and connect a DB-25 "all wires straight through" cable from the digitizer to a COM port on your PC. Adjust R24 and R8 to their midpoints. Turn the digitizer power switch on. Run the program ADJUST.EXE, provided with this toolkit. Press the <F2> key until the display indicates the COM port number to which the digitizer is connected. Adjust R24 until the DC offset reading on the screen is zero. The signal level reading should be flickering slightly, and should be less than about 20. Don't expect zero here. Speak into the microphone, and the signal level should momentarily jump up to a much higher value. Adjust R8 so that the "clipping" indicator LED on the digitizer board flickers on during the loudest peaks of normal speech. The digitizer should at this point be working correctly. If the noise level (idle signal level) is too high, one or more of the following could be the cause: (1) Room background noise; try turning off fans, air conditioners, etc. Also keep the microphone away from the PC itself. (2) Local sources of radiated electrical noise. Common culprits are video monitors, transformers, and particularly desktop fluorescent lamps. (3) Excessively noisy power supply. (4) U1 is defective or has a bad solder joint. (5) Improper connection of power supply bypass capacitors. As a final test, press the <Esc> key to exit from ADJUST, then execute VDFE. Press the <F2> key until the display indicates the COM port number to which the digitizer is connected. Then press the <F3> key, wait until VDFE says "go" (one second later), and say a few words into the microphone. Press the spacebar to end the recording, then press the <F4> key to play it back. You should hear the recording played through the PC speaker.