Interfacing a Switch Figure 4: Reading a switch is very useful because a switch is widely used and can also represent a wide range of digital devices in real world like push buttons, limit sensors, level switches, proximity switches, keypads a combination of switches etc.
We can therefore characterize it according to two quantities: To a fairly good first order, the light output of the LED, either in photons per second or in milliwatts, is linearly proportional to the current through it.
This means that it is useful to think of the LED as a current-operated device. Of course, we could think about it as either; but there is a nice relation between the light output, which is what we ultimately care about, and the current; this is not true for the voltage. To characterize a particular LED, we can apply a voltage for example, using a DC Microcontroller interfacing supplyand note the current through the LED using an ammeter, or perhaps the ammeter built in to our power supply.
This is a relatively typical red LED. We can see that the Microcontroller interfacing between the LED's current and voltage is not very nice—it is not a straight line through the origin, or any other curve with a simple equation.
Over the range of currents at which we expect to operate the LED tens of mAthis curve is very steep. Going from a voltage of 2.
That means that the current through the LED is very sensitive to the voltage across it. Equivalently, the voltage across the LED is very insensitive to i.
This means that to a good approximation, we can model the LED as a constant voltage drop and indeed, many manufacturers' datasheets do not bother with a curve, and quote only a single voltage. If we wanted to model the LED's V-I characteristics more accurately, then we could do that as a series combination of an ideal diode and a resistor.
The ideal diode has an exponential V-I characteristic; that is what is responsible for the non-linear part of the curve near 1.
There is also an ohmic i. That is the reason why the curve shown above seems to approach a straight line at high current. But, we will hardly ever need that good of a model. In any case, you already know that the circuit is this: That was important for TTL an old kind of logicwhich could sink more current than it could source.
For CMOS it does not matter. When it is driven low, zero volts appear across the series circuit, and no current flows. When it is driven high, 5 V appear across the series circuit.
The LED drops about 2 volts; as we saw above, the voltage dropped by the LED is not very sensitive to the current through it, which means that we can get a very good approximation of the voltage dropped by the LED, even before we know the current through it.
We see from the datasheet that the LED is rated for a maximum continuous forward current of 30 mA, so we are well within the spec.
We're not done, though. The LED's nominal voltage drop at 20 mA or any current close to that is 2. This means that while the black curve below which is identical to the black curve above corresponds to a nominal device, a device whose V-I characteristics were described by the blue curve—or any curve lying between those two boundaries—would still meet the manufacturer's spec.Input/output ports P0, P1, P2 and P3 use to interface microcontroller with external devices.
I have already explained it above.
microcontroller features. microcontroller have following basic components inside it or it provides following features.
Although we . In this tutorial we will see How to Interface a 16×2 character LCD module with PIC 16FA Microcontroller using MPLAB X IDE and MPLAB XC8 C Compiler.
Microcontroller Interfacing Techniques Document Revision: Date: 3rd April, Blue Ridge Road, Missouri City, Texas USA Telephone: Fax: - A bit ARM7 microcontroller is used in interfacing and software examples. - Interfacing principles apply to other ARM microcontrollers and other non-ARM microcontrollers as well.
Microcontroller Interfacing Techniques Document Revision: Date: 3rd April, Blue Ridge Road, Missouri City, Texas USA Telephone: Fax: microcontroller interfacing circuits revolution Revolution Education Ltd. Business Innovation Centre, Innova Park, Mollison Avenue, Enfield, Middlesex, EN3 7XU Tel: Fax: Email: [email protected] Web: arteensevilla.com Interfacing is one of the important concepts in microcontroller because the microcontroller is a CPU that can perform some operation on a data and gives the output. However to perform the operation we need an input device to enter the data and in turn output device displays the results of the operation.
- Example programs are written in the C programming language.3/5(1). microcontroller interfacing circuits revolution Revolution Education Ltd. Business Innovation Centre, Innova Park, Mollison Avenue, Enfield, Middlesex, EN3 7XU Tel: Fax: Email: [email protected] Web: arteensevilla.com Microcontroller Interfacing Examples.
Each article in this section describes how to interface a specific item like sensors, displays, storage, communication modules etc. with common microcontrollers like AVR series from Atmel or PIC series from Microchip..
The articles are written for novice audience who don't have much technical experience.