Circuit details The full circuit details for the LED Strobe and Tachometer is shown. It consists of a PIC16F88-I/P microcontroller (IC1), a 16×2 LCD module and not much else. So, in spite of the seemingly complex operation, the circuit itself is really very simple.

Most of the ‘smarts’ are hidden inside the micro, which is really the heart of the circuit. It runs at 20MHz using crystal X1 as its timebase, and this signal is also divided by four to derive the 5MHz oscillator that’s used for the RPM calculations.

In operation, IC1 monitors the external trigger signal (if one is present) at its RB0 input (pin 6), while RB1, RB3 and RB2 monitor the Up, Down and Mode switches respectively. In addition, IC1’s AN4 analogue port monitors the position of potentiometer VR1, which is used for fine RPM adjustments.

Note that RB1 to RB3 have internal pull-up resistors, so these inputs are normally pulled high to +5V. When a switch is closed, the associated input is pulled to 0V and so IC1 can detect this button press.

IC1 also directly drives the LCD module. RA0 to RA3 are the data outputs, while RB6 and RB7 drive the register select and enable lines respectively. Trimpot VR2 sets the display contrast voltage.

When IC1 is operating in trigger mode, the signal applied to the RB0 input (pin 6) is used as the trigger for RPM measurements. This input is protected from excessive current using a 1kW series resistor, while a
1nF capacitor filters out any transient voltages to prevent false counts.

The external trigger circuit is connected via a 3.5mm jack socket and is fed with a +5V rail via the socket’s
ring terminal and a 2.2W resistor. The tip carries the external trigger signal and in the absence of signal, is pulled high via a 10kW pull-up resistor to the +5V rail.

Potentiometer VR1 is connected across the 5V supply and the wiper (moving contact) can deliver any voltage from 0V to 5V to the AN4 analogue input of IC1. IC1 converts this input voltage to a digital value to set the fine frequency adjustment over a 100 RPM range (but only when IC1 is operating in the generator mode).

Note that the operational range of VR1 has been deliberately restricted to 0.54V to 4.46V. This has been done because potentiometers often have abrupt resistance changes towards the ends of their travel. Using a 0.54V to 4.46V range ensures that the more linear section of the potentiometer is used.


SpO,) will flash
the most recent reading and an audible alarm will be issued.
Pressing the Alarm Silence switch (causing the integral LED
to be lit) silences the audible alarm for 2 minutes, but the
alarm display reading and SILENCE LED indicator will
continue to flash at the same rate.
System Alarms
System alarms alert the operator to certain abnormal
conditions or internal system failures. Pressing the rotor
cancels the alarm information box which is displayed on the
LCD. Codes for different procedural and system alarms are
on the next page.
Failsafe Alarm
The failsafe alarm, which is the most powerful alarm of the
PRO Monitor, indicates a serious failure of the Monitor.
This alarm occurs immediately upon any failure of a self-test
and indicates system failure. When the failsafe alarm occurs,
the Monitor disables all features to ensure patient safety.
Alarm Codes
All alarm indications are accompanied by an audible signal
unless Alarm Silence is selected.
A microprocessor system failure will generate a high-pitched
audible alarm regardless of the setting of the Alarm Silence
There are three categories of alarms: patient alarms, system
alarms, and failsafe alarm.
Patient Alarms
Patient alarms include those alarms issued when the
patient’s systolic pressure, diastolic pressure, pulse rate, or
oxygen saturation is outside the set limits. Whenever one
of these conditions occurs, the associated display


This is Lenovo's foray into the affordable tablet market, and is just currently available in the U.S. The A1000 has a dual-core 1.2GHz MediaTek MT8317 processor, with 1GB of RAM, 16GB of internal storage, one front-facing camera (the A3000 also has a 5MP camera on the rear) and support a microSD card.

Both devices sport rather basic 7-inch 1024 x 600 resolution displays but do run the latest iteration of Android, Android 4.2 Jelly Bean. Tablet with no support for GSM voice communication, SMS, and MMS. This is not a GSM device, it will not work on any GSM network worldwide.

It is a fairly thick slab with quite the bezel surrounding the 7" 1024x600 pixels display, which is not IPS, hence with weak viewing angles. The A1000 has a microSD slot in addition to the 16 GB of internal storage, and two front speakers with surround sound technology.

The model operated well and we didn't have time to thoroughly test out how media rattled the dual core in the A1000. From what we saw apps and music playback were no problem for either.

The Lenovo IdeaTab A1000 can be ordered from Lenovo’s website for just $149, with a promo code applied.

General2G NetworkN/A
Announced2013, January
StatusAvailable. Released 2013, May
BodyDimensions199 x 121 x 10.7 mm (7.83 x 4.76 x 0.42 in)
Weight340 g (11.99 oz)
DisplayTypeTFT capacitive touchscreen, 16M colors
Size600 x 1024 pixels, 7.0 inches (~170 ppi pixel density)
SoundAlert typesN/A
Loudspeaker Yes, with stereo speakers
3.5mm jack Yes
- Dolby Digital Plus sound enhancement
MemoryCard slotmicroSD, up to 32 GB
Internal4/16 GB, 1 GB RAM
WLANWi-Fi 802.11 b/g/n, Wi-Fi hotspot
BluetoothYes, v3.0
USBYes, microUSB v2.0, USB On-the-go
SecondaryYes, VGA
FeaturesOSAndroid OS, v4.1 (Jelly Bean), upgradable to v4.2 (Jelly Bean)
ChipsetMTK 8317
CPUDual-core 1.2 GHz Cortex-A9
MessagingEmail, Push Email, IM
JavaYes, via Java MIDP emulator
ColorsBlack, White
- SNS integration
- MP3/WAV/WMA/AAC player
- MP4/H.264/H.263 player
- Document viewer
- Photo viewer/editor
- Organizer
- Predictive text input
BatteryNon-removable Li-Po 3500 mAh battery
Stand-byUp to 336 h
Talk timeUp to 8 h


Conventional dimmers use an electronic switching device to turn the voltage on 120 times every second in a 60-Hz system or 100 times every second in a 50-Hz system, varying the length of time the voltage is held on compared to the length of time it is held off.
The duration of the on cycle, from 0 to 100%, determines the dimming level. This method of controlling the dimming level by varying the duty cycle of the voltage waveform is called phase-control dimming.

In Figure below, the switch at the bottom of the illustration turns on and off twice during each cycle: it turns off at 0° and on at 45°, then it turns off again at 180° and on again at 225°.
It repeats this sequence for every cycle of the voltage sinewave until the dimming level changes. Note that the switching in the negative half cycle mirrors that of the positive half cycle. Otherwise, the voltage waveform will generate a DC offset, which can damage the components in the circuit.
The switching device is either a triac or a silicon controlled rectifier (SCR). Both are solid-state switches that are controlled by a low-voltage control signal. The control signal originates at the lighting console, which outputs a low-voltage digital signal that is sent to the dimmer.
The processor in the dimmer takes the output of the console and translates it to a timing signal that is referenced to the zero crossing of the AC voltage. That timing signal turns the switch on at precisely the right phase angle relative to the sinewave.
The voltage is turned on, and when the phase angle reaches 180° in the positive half cycle or 360° in the negative half cycle, the voltage goes back to zero and stays off until the next switching cycle. The resulting modified voltage waveform corresponds to a particular dimming level.

A triac is a bi-directional switch, meaning it can conduct current in both the positive and negative directions. On the other hand, an SCR is a uni-directional switch; it can conduct in only one direction. In order to conduct for the full voltage cycle, dimmers that use SCRs have two devices connected in parallel and inverted in polarity.
That way, the first conducts during the positive half cycle while the second is off, and the second conducts during the negative half cycle while the first is off. SCRs are more robust than triacs, and therefore dimmers with SCRs tend to be more robust than dimmers with triacs. On the other hand, SCRs are more expensive than triacs.

When the voltage is switched on during the middle of the cycle, the current rises very quickly to catch up with the voltage. As a result, it produces a current spike and overshoots the level where it should be.

The sharp edges of the modified waveform cause mechanical vibration of the filament, which produces an audible frequency referred to as filament sing. The frequency and amplitude are dependent upon the dimmer level and the resonant frequency of the filament. It’s loudest when the
dimming level is about half.

To help mitigate this problem, a choke is placed in series with the load to limit the flow of current. A choke is nothing more than an inductor, soconventional dimmers present an inductive load to the supply.
The larger the choke, the greater the inductive reactance and the more it slows down the current. The rise time is a measure of the effectiveness of the choke; it’s measured in microseconds, or μsec (10–6 seconds). The greater the risetime, the less mechanical vibration the filament experiences.
In North America, inexpensive dimmers can have a rise time of about 80 μsec or less, and standard dimmers usually have a rise time of about 350 μsec. Improved performance dimmers have a rise time of about 500 μsec, and high-rise time dimmers have a rise time of up to 800 μsec.
Of course, bigger chokes cost more to produce; therefore, high-rise dimmers are sold at a premium. They’re also heavier because they have more copper windings.


LCD or flat panel computer displays are the latest and greatest offerings in the desktop computer industry. They have been used for years in the portable and notebook computing markets, but recent developments have increase performance and size while reducing costs making them viable in the desktop environment. LCD displays are lightweight, extremely thin and use much less power than CRT based monitors.

LCD panels are used in various applications ranging from smaller portable electronic equipment to larger fixed location units. Applications such as the display device for digital watches, portable calculators, LCD Monitor and TV, laptop and notebook, arcade game machines, automobile navigation systems, industrial machine, video and digital cameras.

Life span, this is typically the time taken (viewing hours) for the average backlight to dim to 50% of their original brightness. Generally, LCD monitors last longer than CRTs. A typical LCD lifespan is 50,000 hours of use compared to 15,000 to 25,000 for a CRT. A longer monitor lifespan can provide a better return on investment.


Integrated circuits (ICs) are classified according to their levels of complexity: small-scale integration (SSI), medium-scale integration (MSI), large-scale integration (LSI) and very large-scale integration (VLSI). They are also classified according to the technology employed for their fabrication (bipolar, N metal oxide semiconductor (NMOS), complementary metal oxide semiconductor (CMOS), etc.).

The design of integrated circuits needs to be addressed at the SSI, MSI, LSI, and VLSI levels. Digital SSI and MSI typically consist of gates and combinations of gates.

These standard gates are designed to have large noise margins, large fan out, and large load current capability, in order to maximize their versatility. In principle, the basic gates are sufficient for the design of any digital integrated circuit, no matter how complex. In practice, modifications are necessary in the basic gates and MSI circuits like flip-flops, registers, adders, etc., when such circuits are to be employed in LSI or VLSI design.

For example, circuits to be interconnected on the same chip can be designed with lower noise margins, reduced load driving capability, and smaller logic swing. The resulting benefits are lower power consumption, greater circuit density, and improved reliability. On the other hand, several methodologies have emerged in LSI and VLSI design that are not based on interconnections or modification of SSI and MSI circuits.

The effort required for the design of an integrated circuit depends on the complexity of the circuit. The requirement may range from several days effort for a single designer to several months work for a team of designers. Customdesign of complex integrated circuits is the most demanding. By contrast, semicustom design of LSI and VLSI that utilize preexisting designs, such as standard cells and gate arrays, requires less design effort.

IC design is performed at many different levels. Level 1 presents the design in terms of subsystems( standard cells, gate arrays, custom subcircuits, etc.) and their interconnections. Design of the system layout begins with the floor plan of level 3. It does not involve the layout of individual transistors and devices, but is concerned with the geometric arrangement and interconnection of the subsystems.

Level 4 involves the circuit design of the subsystems. Levels 2 and 5 involve system and subcircuit simulations, respectively, which may lead tomodifications in levels 1 and/or 4.

Discussion here will focus primarily on the system design of level 1 and the subsystem circuit design
of level 4. Lumped under the fabrication process of level 7 are many tasks, such as mask generation, process simulation, wafer fabrication, testing, etc. Broadly speaking, floor plan generation is a part of layout. For large ICs, layout design is often relevant to system and circuit design.