Abstract: This article will introduce that one kind disseminates news the voltmeter based on monolithic integrated circuit’s pronunciation, this system may carry on the comparison high accuracy to the DC voltage the survey and disseminates news this value with the pronunciation. At the same time, may also through changes in ADC REF (-) and REF ( ) the value realize to the different scope DC voltage survey.
Key word: Monolithic integrated circuit The pronunciation disseminates news a/d conversion (ADC) voltmeter
Introduction
The traditional voltmeter played its unique role in ours daily life and the scientific research, but in the science and technology changes with each new day, integrated chip appears in daily life application more and more widespread today the comparison falls behind:①Their measuring range often in leaving the plant before defines well, cannot act according to the concrete use situation to make the corresponding adjustment;②The measuring accuracy is limited;③Cannot broadcast the measurement result with the pronunciation. This article will introduce that one kind the monolithic integrated circuit type pronunciation which by monolithic integrated circuit smallest system [1][3], mold - number switching circuit [3] [5], pronunciation electric circuit [2][4], LED display circuit [1][3] is composed disseminates news the voltmeter.
1st, hardware design
Overall system’s composition may divide into four major parts: Monolithic integrated circuit, mold - number switching circuit, pronunciation electric circuit, LED display circuit. Below carries on the concrete introduction on the main part.
1.1st, monolithic integrated circuits
At present is popular the monolithic integrated circuit are many, the 89C51 bringing has internal ROM and certain amount RAM, generally does not need to expand outside the piece the memory, and can be compatible with the MCS-51 product. This design chooses the 89C51 monolithic integrated circuit, the following chart shows: 
Figure 1-1 89C51 monolithic integrated circuit
This design selects the simple basic classics reset circuit, it uses the electric capacity and the resistance charging and discharging produces one to meet the time requirements the continual low voltage, and inputs to monolithic integrated circuit’s replacement base pin.
1.2nd, mold - number switching circuit
The mold - number transformation chooses 8 ADC is AD0809, the module distribution like chart 1-2, the measuring range the voltage which and REF( ) meets by REF(-) decided that use time may act according to the concrete demand to change the survey measuring range.
The principle of work is as follows: First, in the address control module, sends the channel which by the monolithic integrated circuit “the channel control signal” chooses us to need, afterward the ALE signal locks this channel. This time, the outside analog input may pass “the analog input switch” to enter the AD switch. By now, the START signal one effective so long as started to carry on the AD transformation immediately.
AD transforms the process is actually one “and the reference voltage comparison, approaches gradually” process. The module provides the reference voltage by “256 resistance steps and ladders”, and in “switch arrays” under the control, carries on the comparison with the input, until in “S.A.R.”In the module obtains a quite precise digitized value of exports, by now transmitted the EOC signal by “the control/fixed time module” to inform the exterior AD transformation to finish. Arrives the digital signal saves in “outputs the lock to save the module”, so long as the monolithic integrated circuit comes OUTPUT the ENABLE signal then output data.
Figure 1-2 ADC module chart
The ADC chip is as follows:
Figure 1-3 ADC chip chart
The mold - number transformation work is mainly completes by the hardware, its software part is quite simple.
the 1.3rd, pronunciations disseminate news
From design request, chip aspects and so on performance considered, when design has chosen ISD1400. Its function is complete, the control signal only uses 89C51 the I/O pilot wire. Contains 64K/128K the EEPROM memory, the noise elimination microphone Pre-amplifier and the automatic gain control AGC electric circuit, the suitable pronunciation special-purpose filter circuit, to have the extremely high temperature control performance clock oscillating circuit and the complete pronunciation processing electric circuit. This kind of electric circuit has also raised many kinds of application mode selection and the connection, and may apply in conveniently each kind of integrated electron phonetic system. The pronunciation recording and sending out module may use in each kind of section of type pronunciation message installment, the pronunciation warning and in the voice prompt installment, can in the situation which the power source separates, long-term preserved information. When design the concrete connection is as follows:
Figure 1-4 phonetic system
ISD1420 may partition stores 20 second pronunciation information, may read 3 Chinese character computations according to each second, 20 seconds may partition store more than 609 Chinese character pronunciations. ISD1420 A2~A7 and the monolithic integrated circuit CPU I/O mouth connection, may withdraw 64 section of pronunciation information alone like this, and may combine certain section of complete length sentence automatically under software’s support. Puts through the power source, the electric circuit enters the electricity saving ready condition automatically. Holds down records the key (REC maintains low level), the electric circuit enters the recording condition, records the indicating lamp to be bright, changes until REC high or the memory records fully, the recording conclusion entered the ready condition. The sound recording finished then uses.
1.4th, LED demonstration plan
Demonstrated that the plan commonly used has two kinds: Serial port and mouth. Because designs, regarding the 89C51 I/O mouth use intense relations, we selects the serial port to demonstrate. For can simultaneously demonstrate that 3 LED nixietubes, this system needs to increase three 74LS164 to make the string - - and transforms. At the same time, as a result of voltage relations, but also needs to add on the limiting resistor. Has the hardware and the software two ways in the decoding aspect, to reduce hardware’s complex degree, the design uses the software table look-up decoding the method.
2 Software design
Software’s design implements the modulation, mainly by a/d conversion, the error judges (, if has measured identical value is error is very small two times does not disseminate news), the code system to transform, the LED demonstration, the pronunciation to disseminate news several big module constitutions. Software
The flow chart is as follows: 
3rd, software debugging
This system’s software system uses C51 to compile completely, because the common simulator the support has certain flaw to C51, the software debugging is quite complex. Besides grammar mistake, when confirmation procedure not question, through downloads directly to the monolithic integrated circuit debugs. What adopts is from under to debug method, namely debugs each module alone, then connects a complete system debugging again.
4th, hardware debug
When debugging uses the standard power source, digital multimeter the DT9505 digital multitester may the decision system survey precision. System power line voltage: 5V (standard)
To the data which measured carries on the analysis to be possible to draw the following conclusion: Supply power with the standard 5 volts voltages, measured the voltage only has 0.01 volts error in the individual voltage range, other scopes do not have the error nearly. As a result of the software algorithm’s limit, the biggest error in 5 volts place, is 0.02 volt.
5th, software and hardware jointing shake down testing
Through establishes simulator’s attribute, thus realizes software and hardware jointing shake down testing through the simulator. Corresponds each module function to realize in the hardware circuit, through simulator’s single step or the break point execution and the full speed execution, observes hardware circuit’s response to be whether normal. To the question which appears makes the revision and the improvement in the debugging process, builds the foundation for hardware’s off-line movement.
Welding hardware circuit in earnest inspection foundation, but must grasp the welding the time. In order to avoid the faulty soldered joint, the request soldering tin and the wire contact fully, but we use the rubber wire, the excessively high temperature will cause the rubber to fall off, in the situation easy to create two wires with other transposition the pipe nipples, will have the unreliability. When welding, also easily burns out stand’s plastic material.
The use analog simulation and a use real simulation debugging a little distinguishes. Analog simulation debugging time the hard accent breakdown which is not easy presents when a real simulation debugging to produce. Real simulation must receive hardware circuit’s signal of stop, and enters the interrupt servicing subroutine to complete the corresponding movement. Therefore, in this design software originally should use the timer precise time delay the place, can not but use the software time delay, causes the design not to be able to use the resources fully, has increased the CPU burden.
6th, conclusion
The research disseminates news the voltmeter based on the MCS-51 monolithic integrated circuit’s pronunciation, uses the serial port to expand (the LED part), the real-time transformation (the ADC part), technologies and so on pressed key replacement, may carry on the comparison high accuracy to the DC voltage the survey and disseminates news this value with the pronunciation. System’s movement is reliable, is stable. May see to the system measurement result analysis: When with standard 5 volt voltage power supply, measured voltage error in 0.01 volts scope.
Voltmeter’s range adjustment is also very convenient, in the actual utilization process, the different user may according to own actual need, change REF (-) and REF ( ) the value then may the scale range adjustment.
7th, reference:
[1] nation university student electron design competition organization committee. The fifth national university student electron design competition award compiles Beijing: Beijing Institute of Technology Publishing house
[2] winbond. ISD1400 Series Single-Chip Voice Record/Playback Devices 16-and 20-Second Durations. America: Electronics Corporation America
[3] Shanghai Panel of educators group Ding Yuanjie. Monolithic microcomputer principle and application Beijing: Mechanical industry publishing house P176 –185 P200 —204
[4] http://www.21cm.com.cn/product/zy1420/ISD1420shouce.pdf
[5] http://stocks.find-ic.com/search.asp?p=AD0809
