Readouts

You must be able to recognise components such as capacitors, diodes, zeners, transistors and resistors to build 5x7 Display project. This information is covered in our BASIC ELECTRONICS course and a complete set of circuit symbols can be found HERE.

This sign I designed uses no microprocessor. It has an eprom and multiple counters. As in most electric signs, the LEDs are matrixed, and strobed very quickly to make it possible for all 70 LEDs to appear lit. This sign is strobed horizontally, unlike most large signs which are strobed vertically. I did it this way because electrically it was simpler. The eprom has 8 outputs, of which I used 7 of them to drive the 7 horizontal rows. The eprom outputs are not strong, so they are buffered. The 10 vertical columns are activated in sequence, giving a 1/10 duty cycle.

This sign I designed uses no microprocessor. It has an eprom and multiple counters. As in most electric signs, the LEDs are matrixed, and strobed very quickly to make it possible for all 70 LEDs to appear lit. This sign is strobed horizontally, unlike most large signs which are strobed vertically. I did it this way because electrically it was simpler. The eprom has 8 outputs, of which I used 7 of them to drive the 7 horizontal rows. The eprom outputs are not strong, so they are buffered. The 10 vertical columns are activated in sequence, giving a 1/10 duty cycle.

A very simple circuit to experiment with AT90S2313, 2x16 LCD display and 4x4 keypad. The clock based on 4 MHz crystal, but you can use anyone crystal between 1-4 MHz. The keys with the name "A", "B" ... "F" are typed to the LCD with numbers 10-16. Because the AVR have only 15 I/O pins we are working the LCD display with 4-bit databus. The 4 resistors (10K) are to protect the AVR from the shortcuts as the coloumn of the keypad is change. I make the source code with a simple form, that its mean I don't make any economy to the memory, to understand the beginner how does the circuit its working.

The circuit in Figure 1 uses a PIC16C55 µP to read 10-bit binary data and directly display the data in decimal format on three common-cathode LED displays. If value of the data exceeds 999, the displays show three hyphens (---) to represent overflow. The PIC16C55 has high drive capability. Each output pin can source 20 mA and sink 25 mA; the outputs can thus directly drive the LED display.

The circuit in Fig 1 provides digital control and automatic thermal compensation for LCD contrast bias. This control and compensation eliminates the need for panel-mount hardware and frequent manual adjustment of LCD contrast in changing temperature environments. Major components in Fig 1 include an inverting current-mode PWM regulator, a programmable digital potentiometer, and a negative-temperature-coefficient (NTC) thermistor. The 5V single-supply circuit consists of all surface-mount components and occupies approximately 6.25 sq cm of board space.

HamCam-ID'er is a tiny digital voice playback device that is designed to announce your personal ham call letters every few minutes. Its small size is perfect for mounting on video equipped R/C model aircraft.

Vacuum fluorescent displays, known as VFDs(because both vaccuum and fluoroscent are hard to spell) are commonly used in VCRs and microwaves. They are relatively bright and have a low power consumption. Some older calculators used them before LCDs became popular. Having obtained a few Futaba VFDs from a surplus dealer, I went about trying to interface it to a PIC. A plea went out on the PIC list and was soon answered by Kalle Pihlajasaari with a few details on VFDs.

This is the first interfacing example for the Parallel Port. We will start with something simple. This example doesn't use the Bi-directional feature found on newer ports, thus it should work with most, if no all Parallel Ports. It however doesn't show the use of the Status Port as an input. So what are we interfacing? A 16 Character x 2 Line LCD Module to the Parallel Port. These LCD Modules are very common these days, and are quite simple to work with, as all the logic required to run them is on board.

This is one of the most accurate and simplest LC inductance / capacitance Meters that one can find, yet one that you can easily build yourself. This LC Meter allows to measure incredibly small inductances starting from 10nH to 1000nH, 1uH to 1000uH, 1mH to 100mH and capacitance from 0.1pF up to 900nF. LC Meter's circuit uses an auto ranging system so that way you do not need to spend time selecting ranges manually. Another neat function is the "Zero Out" switch that will reset the initial inductance / capacitance, making sure that the final readings of the LC Meter are as accurate as possible.