If will do this only if the value of TIME is reset to zero as shown. The Expression command is used to give a value to a variable as a flowsheet runs. The variable is given its value as flow passes through the command. The following examples show how it can be used. A value can also be given to a variable in the form of a mathematical expression as shown in the flowsheet in fig 5. This system counts the number of times that two separate switches are pressed, and displays the combined total.
A container in a warehouse is designed to hold ten packs of components. A system is needed to indicate the changing contents of the container as packs are removed. A digital sensor is used to indicate each time a pack is removed notice the use of two Digital Decision commands to ensure a clean count.
The number of packs in the container is displayed as a binary count using 8 LEDs connected to outputs of the PIC microcontroller. The DEC command counts down, so an Expression command is used to set the value of variable A to 10 at the start of the countdown when the container is full.
The Expression command Cell Details box is shown in fig. SHR 2 means divide the value of A by 4, and so on. Use SHL in the same way to multiply the value of a variable. The flowsheet in fig 5. The IN command sets the value of a specified variable to the current binary value of the input port. So, for example, if switches connected to inputs 0 and 1 are pressed, then the value of the variable will be 3. If any other combination of switches is pressed, flow goes in the N direction.
The RND command Each time flow passes through this command, the selected variable is given a random value between 0 and In the example shown in fig 5. Every second the display will change at random.
So,when the PIC microcontroller is reset or powered up, all variable values are reset to zero. The following information explains how this works. The READ command takes the value which is currently stored in a selected address in this case address 0 , and puts it into the selected variable in this case variable A.
When it is powered up, the first thing that happens is that the READ A,0 command retrieves the value of A which has been stored in address 0. Each one can store a number between 0 and Any values shown will be saved when you save the flowsheet. They will also be downloaded with the flowsheet. Therefore, when you have test run the flowsheet, make sure that you edit the values shown in this window back to zero before you download the flowsheet - unless, of course, you want to download the current values for some reason.
A PIC microcontroller is a programmable device, which means that it is able to store sets of instructions in the form of a program, and carry out the instructions whenever the program is run. It is written in hexadecimal and is difficult for anyone other than a trained programmer to use. So, a programming language is used to allow designers to create, edit and download instructions to the chip. The machine code is generated automatically from the programming language.
A PIC microcontroller is a single chip that can be programmed to switch output devices on and off in sequences and in response to input from sensors. A microcontroller contains all the elements of a microprocessor system. In a microprocessor system, each of these elements will be in the form of one or more individual chips. However, the PIC microcontroller combines all of these elements in just one chip, that processes instructions as well as controlling devices.
Programming languages PIC programming languages come in many different formats. The disadvantage of high level languages is that programs require more memory space and run more slowly than low level ones. Low level languages for example, assembler code require a much deeper level of understanding of how the chips actually work. Their commands are complex and sometimes obscurely titled. The lower the level of the language, the nearer it is to the machine code and the harder it is to understand.
On the other hand, the benefit of using a low level language is that the finished code is normally very concise and therefore runs very efficiently and faster than a higher level language can. The panel on page 42 shows how the same simple program would appear in machine code and in three different programming languages. PICs also vary in terms of how they are programmed and erased. UV light erasable chips are not widely used because they need a special UV light source to erase them and because of the health and safety problems associated with using UV light.
The third type of chip is called OTP one time programmable and, as the name suggests, can only be programmed once. Chips in sizes from 8 pins to 40 pins are available to provide different numbers of outputs and inputs. Some provide digital inputs only. Some have ADC analogue to digital conversion built into them so that analogue sensors can be connected directly to them.
Obviously the larger, higher specification PICs are more expensive, so it is important for designers to select the most appropriate chips for their purposes. Millions of PIC chips are used each year in: electronic consumer goods, mobile telephones, medical equipment, computer products, and industrial applications. There will be, on average, 35 programmable chips in every car, used in a range of sub-systems from engine management to remote locking.
One PIC chip can replace a wide variety of traditional discrete electronic components such as transistors, logic circuits, timer chips. This means that products based on PICs can be smaller and cheaper.
They will have fewer separate parts so they are likely to be more reliable. The company manufacturing the products will have reduced stock levels. Product-assembly will be simpler and therefore quicker and cheaper. Using PICs can make products more flexible. Their features are programmed into the chip, not built into electronic hardware, so they can be developed and changed quickly and easily. If the manufacturer of a product wants to change a feature of the product, a simple change to the PIC program can achieve what is required without the need to alter any of the components on the PCB.
Up to chips can be found in every home, where a typical use would be in a security system in which a PIC might be used to monitor the sensors placed around the house and switch an alarm; as well as enabling features such as the use of a code, input by a keypad, to set and reset the system. A microwave oven may use a single PIC to process information from the keypad, display user information on a seven segment display, and control the output devices turntable motor, light, bell, magnetron.
The main disadvantage of PICs is that they have only a very low power output, of a few milliamps. They therefore require interfacing circuitry to drive higher current loads. The system takes in information from devices used to select different washing programs, and also from sensors that monitor temperature and water levels. It is programmed to make use of this information and switch output devices such as motors, pumps and heaters on and off in appropriate timed sequences.
Once the chip has been programmed it is useless until it is interfaced to the real world. Interfacing involves providing power to the circuit, and using standard interfacing circuits for input and output devices. These include potential dividers for sensors, and transistor drivers for output devices. This section of the book shows the basic interfacing circuits that are likely to be required for most school projects. Arithmetic Logic Unit A separate processor inside the chip to specifically handle mathematical and logic operations.
This is more efficient than having the main processor perform these operations. Random Access Memory Memory that can be accessed as required, with ability to write and read as necessary.
Data stored in RAM is not held if the power to the chip is turned off. All microprocessors operate at a fixed speed which is referred to as speed or clock frequency and is quoted in Hertz Hz. PIC chips normally run at 4Mhz Mega Hertz and in some cases require an external resonator to regulate this speed. Some newer type PIC chips have these resonators built in.
This memory is still stored even if power to the device is switched off and is what makes up most of the data memory in PIC chips.
Analogue to Digital Converter Analogue sensors provide information in the form of varying voltages, usually between 0 and 5 volts. Analogue to Digital Converter chips sample these voltages at regular intervals and convert them to a digital information which is then sent out from the chip using serial data transmission. For example, the PIC16F has 4 analogue inputs which, after conversion, each give a digital value of between 0 and So, there are 2.
The higher the number of bits used for sampling, the higher the accuracy of the conversion. Within each port there are a number of bits designated RAx or RBx where x is the number of the bit which are in effect the physical pins on the PIC.
This is illustrated in the table beside each pin-out diagram. This can be provided by 4 x AA cells. The following diagrams show connection to 18 and 28 pin chips. The nF polyester capacitor is used to decouple the PIC microcontroller power supply for reliable operation. Using two power supplies If your project includes an output device which requires a voltage greater than the 6V that you are using to power the PIC microcontroller circuit, use two separate power supplies as shown in fig.
This is more efficient and economical than using a relay. In some situations it might be more convenient to power your project from a low voltage DC power supply, rather than a battery. If you wish to do this, you should use a voltage regulator as shown in fig. Resonator The PIC microcontroller provides a clock pulse internally.
The resonator regulates the speed of the clock pulse, or in other words, sets the speed at which the PIC microcontroller works 4MHz. Some PIC microcontrollers have an internal resonator. Others need to have a 4MHz ceramic resonator connected as shown in fig. Reset This pin must also be connected to the 6V rail through a 4k7 resistor as shown in fig. You can also include a reset switch as shown in fig. When you press this switch, the flowsheet programmed into the chip will restart at the START command.
Connecting Output Devices Note that diagrams shown in this section show how to connect the output device only. For simplicity, the PIC microcontroller is simply shown as a block. The position of the output pins on the block diagram does not necessarily indicate the position of an output pin on a PIC microcontroller chip.
A: Components that can be connected directly to an output pin The following low current output devices can be switched directly by the PIC microcontroller.
The resistor is required to limit the current through the LED. The bars of the seven segment display can be lit in different combinations to show the ten digits 0 to 9, as well as some letters of the alphabet. A number of different types of seven segment display are available.
You should use a common cathode type. The common pin connects to 0V. Each LED bar has an identifying letter. Consult the pin-out diagram of the seven segment display that you are using, to identify the appropriate pins. Piezo Sounder A piezo sounder can be used to produce a range of different sounds. The sound is created by a pulsed signal. This signal can be sent from any one of the output pins on the PIC microcontroller.
Counter Module A counter module is an LCD numerical display which can be used to show a changing count value. It is powered by its own internal 1. The counter is incremented by a pulse. Use two Outputs commands to create a pulse - one to switch the output on; the other to switch it off. Connect the counter module as shown in fig.
A PICmicro unless pre-programmed with a bootloader cannot be programmed without a hardware programmer. Most PICmicro hardware programmers have software which will allow a. Thank you for your reply. I can create a flowchart and download to a PIC via the Logicator programmer. What I would like to do is download a program in hex format to a PIC using the programmer.
I would like to use the PIC Logicator program, but it only creates the hex download from a flowchart. Comodo Antivirus Terry Save your computer from programs which cause the slowdown of your programs, consuming memory and Website Realizer Nordvald Make an website of your own like a pro in few minutes with Website Realizer which lets you just Free Downloads: Logicator Free.
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Recent Blog Posts. Unread PMs. Forum Themes Elegant Mobile. Essentials Only Full Version. New Member. I've got 5 16F88s and a Economatics - pic logicator, as the programmer. It connects via a serial port, which I only have 1 of, so assuming its com1, with device manager backing that up. I've looked through some sample code and understand that now, so thought I'd try to program the chip for a test. Which unfortunatly was little use in telling me which programmer to choose.
Please verify serial connection and try the current operation again. No programmer detected. Please verify serial connection and try the current operation again" And now I'm stuck, out of ideas.
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