Various Circuits

Normally analogue-to-digital con-verter (ADC) needs interfacing through a microprocessor to convert analogue data into digital format. This requires hardware and necessary software, resulting in increased complexity and hence the total cost. The circuit of A-to-D converter shown here is configured around ADC 0808, avoiding the use of a microprocessor. The ADC 0808 is an 8-bit A-to-D converter, having data lines D0-D7. It works on the principle of successive approximation. It has a total of eight analogue input channels, out of which any one can be selected using address lines A, B and C. Here, in this case, input channel IN0 is selected by grounding A, B and C address lines.

Perhaps the most effective way to gain board space and increase component density is to minimize wiring on the board. A widely used architecture that allows such miniaturization is the I2C bus. Comprising only a bidirectional data line, SDA, and a clock line, SCL, this bus requires no chip selects or other additional connections. Microcontrollers from Philips, Microchip, and other manufacturers include dedicated I2C interfaces, but you can also implement the interface in software. To complete this task, you associate a 7-bit address with each master or slave transceiver and factory- or pin-program the device with two to four address options.

M1 is a stepper taken from an old disk drive. There are five pins, i.e., common, coil 1, 2, 3 and 4. Resistance measured between common pin and each coil is about 75 Ohms. Driving current for each coil is then needed about 60mA at +5V supply. A darlington transistor array, ULN2003 is used to increase driving capacity of the 2051 chip. Each output provides 500mA max at 50V. P1.4 to P1.7, four output pins are connected to the input of the ULN2003 as shown in the circuit. Four 4.7k resistors help the 2051 to provide more sourcing current from the +5V supply. The serial port is optional for your exercises. Many have provided useful technical, and application of using stepper, see the links below.

Some applications may not need user display and key interface, dump terminal is an alternative way for program setting, displaying user interfacing command.Debugging, dump terminal connects with serial port, use only 2-i/o pin, P3.0 for Rxd and P3.1 for Txd. Any computers that has serial port and emulates as a dump terminal can be used for the purpose, the example used PC run terminal emulation program has COM1 9600baud 8data bit no parity, 1 stop bit. standard serial port is RS232C needs level converter from TTL to RS232C by using MAX232 or DS275. D1 is a dot LED used for testing program running.

This circuit was designed to control a 32 channel Christmas light show from the PC serial port. Originally designed with TTL logic, it has been simplified using CMOS circuits to reduce component count. It is a fairly simple, reliable circuit that requires only 4 common CMOS chips (for 8 outputs), an optical isolator, and a few discrete components. The schematic diagram (SERIAL.GIF) illustrates the circuit with 16 outputs which can be expanded with additional 8 bit shift registers.

This circuit is a simple 8-bit analogue to digital converter circuit which is connects to PC serial port. The circuit is based on TLC548 A/D-converter chip (might be hard to get nowadays, Texas Instruments makes this IC), which is an A/D-converter with serial output. The output of the TLC548 is not directly suitable for standard serial data reception, so this circuit uses serial port handshaking lines in a nonstandard way which enables the communication between computer and converter chip to be implemented with as few components as possible. The circuit takes all the power it needs from PC serial port.

This is one of the ways to build an interface between an ericsson 6xx/7xx phone and a PC serial port. This particular interface uses the phone battery as a power supply, another way to do another kind of interface is desiging a circuit wich gets power from the PC serial port, but such an interface would have more components and wouldn't be as safe as this one, because getting power from the serial port is a little risky.

Here is a novel idea for using the printer port of a PC, for con-trol application using software and some interface hardware. The interface circuit along with the given software can be used with the printer port of any PC for controlling up to eight equipment.

The LTC®1387 is a single 5V supply, single-port, logic-configurable RS232 or RS485 transceiver. The LTC1387 features Linear Technology’s usual high data rates (120kBd for RS232 and 5MBd for RS485), a loopback mode for self test, a micropower shutdown mode and ±7kV ESD protection at the driver output and receiver inputs.

Multiport RS-232C PC add-on boards are intended for intensive multichannel communication. Therefore, each serial port has its own transmission controller. If your application doesn't need interrupt-driven service, and polling the devices through RS-232C channels one after another is sufficient, then you can use a single controller with switched input and output signals instead of installing a costly multiport adapter.

If you are looking at this page, you probably feel like I did when I tried to run a self-powered PIC programmer with my notebook computer. Yes, the serial port was the ultra-low-power type and wouldn`t provide enough current to power the programmer. The problem was clear and so was the solution. I could have modified the programmer to get the power from somewhere else, but in the future I΄d crash with the same wall. I needed something to interface the low-power serial port to the hungry programmer.

The joystick button inputs can be used as general purpose button or switch inputs, and can also be driven by logic level signals or by open collector or open drain logic outputs. If used with a signal direct from a mechanical contact (e.g. a switch, microswitch, contact, or pushbutton), remember that the joystick port does not perform hardware debouncing, so this must be provided by external hardware or provided by software.

This is a page of analogue interfaces for joysticks. Although these interfaces have been developed for use with 4QD's controllers they will have plenty of other uses. Also because of the development history, we have printed circuit boards available (either fully populated and tested) or bare boards) for these interfaces. All of 4QD's Motor Controllers require a speed input (typically 0-4 volts) and a separate direction input, so that is what these interfaces provide. Circuits are provided but as some of these are quite large, as links rather than as embedded GIFs. The index allows you to jump direct to the appropriate section.

If you have access to a Lowe HF-225 shortwave receiver, then you might be interested in this page. If you don't, then you'd probably be better off leaving now. What follows is a project I completed some time ago, which allows the Lowe HF-225 to be controlled from a PC, or other device with an available RS232 port. The Rx has an input for a remote keypad, and, consequently, was begging for me to hook my PC up to it. I don't feel the need to spell out the advantages, since you obviously understand or you wouldn't have found this page. In summary though, the combination of hardware and software presented here allows me to select frequencies using mouse clicks, configure preset frequency buttons , log significant events and scan up and down through the frequency range using predetermined step sizes and rates.

RS-485 communications can provide longer range and better noise immunity than RS-232, as well as multidrop capability. Because it does not have separate transmit and receive lines, RS-485 requires flow control. RS-232/485 converters often use one of the RS-232 handshaking lines to control direction, but several communications-software packages do not support flow control. The circuit in Figure 1 is an RS-232/485 converter that uses the transmitted signal itself to control the flow.

The circuit is basically a two transistor buffer consistong of transistors Q1 and Q2 which can drive up to 1A current pulses, but the maximum putput current of the circuit is limited by resistor R2. Value R2 was experimentally selected by testing resistor values in range of 22 ohm to 270 ohm and value 140 ohm gave best results (it provides quite good impedance matching to cable used). It is a good idea to use at least 1W resistor in place of R2 to make sure that it does not overheat in output short circuit situation (RS232 devices must withstand that to meet the standard).

Laser based projects used to be expensive, until the development of solid state lasers. This project is designed for the entry level laser experimenter. The circuit allows any two computers with serial (RS-232) communication capability to communicate over 200 meters using a laser beam. A low cost transmitter only circuit is also presented here for use in one way communication and other laser based projects.

I got a problem with my notebook, because it has only COM1. My programmer board, Easy-Downloader must use serial port and the application board also needs to communicate via the same serial port. I do remembered I have to swap DB9 connector of both devices many times. So I spent 30 minutes built above simple hardware. Of course it was not the expander by meaning. But it helps me a lot. Someone may prefer to call it as the rs232 selector, but I like "expander". Above picture is the sample board, no need to make a pcb.

Use nine pieces of hookup wire (or a piece of ribbon cable) to connect corresponding points on the I/O Demonstration Board to the Relay Sub Board. Connect 12 volts DC (smoothed) to the power input points on the I/O Demonstration Board. Solder in as many relays as you intend to use, each with its associated LED, resistor and 1N914 signal diode.

This circuit is a modified version of an original interface on QSL Net. It is a fully isolated interface allowing computer control of the Trio/Kenwood R5000 receiver. Separate software is needed to control the receiver.