Free electronic circuit design and schematic diagram
Telephone line is designed to carry audio signal, which is an alternating current in nature. To transmit measurement signal, which has very low frequency or DC signal, we have to convert the signal into AC with acceptable frequency range for telephone line transmission. For transmitting analog data over telephone lines, its ideal to use the TC9400’s square-wave output. Since the […]
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Power dropout detection is often required by digital system driven from the AC line. A memory store command to be issued before DC power falls is allowed by fast AC line drop out detection. The circuit on figure below detects AC dropout by connecting an optoisolator across the power transformer’s rectified secondary. Normally, the LED is turned on by the […]
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Microphone can’t be directly connected to a power amplifier because the signal is too weak. Standard audio power amplifier accept about 1 Vrms to give a full volume (maximum power), and off course there’s such microphone has such high level output. To provide signal with high enough amplitude, we can use a pre-amplifier circuit shown in the schematic diagram below: […]
Read moreTurning long term integrator into bipolar input introduce a concept similar to “negative frequency”, where the counter would react to decrement its counter when a negative frequency is supplied. Off course there’s no such concept in reality, but we can achieve the same function by rectifying the input before converted to frequency, and detecting the polarity to control the up-down […]
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Measuring charge amount in electroplating, or measuring actual battery capacity can be done with integrator. Special requirement for this integrator is that it should has no leakage for long term operation, ranging for hours to several days. Using a voltage-to-frequency converter and a counter can solve this problem, here is the block diagram of the system: The counting values is […]
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The voltage that control a V/F converters will be displayed if we use a frequency counter, which is directly proportional to the input voltage. A 1 second time base will give 4 digit resolution with 1 reading per second when the V/F converters is running at 10KHz full scale. To transmit the frequency, we can use the optoisolator, so there […]
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