Pro Mini atmega328 3.3V 8M. Blog | RF Remote Control Transmitter and Relay Receiver. Before we discuss how to design RF remote control transmitters using SAW resonator, we have to know the basic principle, how it works. Basically a simple transmitter - oscillator network, contains frequency control part, amplifier and data input for phase shift, the amplifier contains RF transistor and a few surrounding components, and frequency control part contains SAW resonator, part of output signal is feedack into input of amplifier, and insertion loss and phase of feedback depends on frequency. SAW resonators application circuits can be divided into two methods, one-port resonators and two-port resonators, we always perfer one-port resonators since it's simple application circuit and components, and it's easier to source since major manufacturers such as Murata mainly make one-port resonators now.
As the circuit begins to build up the oscillation, the initial values such as DC biasing points, LC circuit and PCB with the antenna apply. SaberElétrico. Na lição anterior conhecemos os princípios simples da Álgebra de Boole que regem o funcionamento dos circuitos lógicos digitais encontrados nos computadores e em muitos outros equipamentos. Vimos de que modo umas poucas funções simples funcionam e sua importância na obtenção de funções mais complexas. Mesmo sendo um assunto um pouco abstrato, por envolver princípios matemáticos, podemos perceber que é possível simular o funcionamento de algumas funções com circuitos eletrônicos relativamente simples, usando chaves e lâmpadas. Os circuitos eletrônicos modernos, entretanto, não usam chaves e lâmpadas, mas sim, dispositivos muito rápidos que podem estabelecer os níveis lógicos nas entradas das funções com velocidades incríveis e isso lhes permite realizar milhões de operações muito complexas a cada segundo.
Você irá começar a tomar contato com componentes práticos das famílias usadas na montagem dos equipamentos digitais. 1 - O transistor como chave eletrônica 2 - Melhorando o desempenho . . Transistor as a Switch - Using Transistor Switching. The Transistor as a Switch When used as an AC signal amplifier, the transistors Base biasing voltage is applied in such a way that it always operates within its “active” region, that is the linear part of the output characteristics curves are used. However, both the NPN & PNP type bipolar transistors can be made to operate as “ON/OFF” type solid state switches by biasing the transistors base differently to that of a signal amplifier. Solid state switches are one of the main applications for the use of transistors, and transistor switches can be used for controlling high power devices such as motors, solenoids or lamps, but they can also used in digital electronics and logic gate circuits.
If the circuit uses the Bipolar Transistor as a Switch, then the biasing of the transistor, either NPN or PNP is arranged to operate the transistor at both sides of the “ I-V ” characteristics curves we have seen previously. Operating Regions 1. Cut-off Region Cut-off Characteristics 2. PNP Transistor Switch. Base current calculator - Google Search. PNP Transistor Switching. The calculations for base current and the base resistor are identical to those outlined in Part 7 for NPN transistors except the polarities are reversed.
One additional thing you need to be careful with PNP high side switches is the voltage used to drive the load. Normally it is best to use the same voltage to drive the load that is used to power the microcontroller. Consider the following. Suppose the load voltage is +12V and the microcontroller is running at 5 volts. Ignore R2. R2 would normally have a value high enough to have little effect and ignoring it makes the calculations that follow simpler. Ib = (Vcc – Vp0 – Vbesat)/R1 =( 12 – 5 - .7)/1000 = .0063A = 6.3ma Unless the transistor has exceptionally low gain, it will be turned on even though with P0 high it should be turned off. Driving high power loads with transistors.
We will use a 2K resistor for R1. There are two more components in Figure 7-2 we have not accounted for, D1 and R2. D1 is a diode to snub the current spike from the inductor coil. A lot of energy is stored in the magnetic field of the relay coil when it is energized. When we turn off the relay, that energy has to go somewhere. The diode type is not too particular. The remaining component is R2, and may not be needed in some applications. Let’s take a closer look the voltages across the relay and transistor. Vcc = Vrelay + Vcesat Vrelay = Vcc – Vcesat = 12 – .3 = 11.7V But our relay is a 12V relay! It might seem to be a lot of work to calculate all this.
PNP Transistor switching. Since 198 ohms is not a standard resistor value we will use a 220 ohm resistor. I might consider using a the next standard value resistor less than 198 ohms to increase the current and improve the margins. The problem here is that 50ma is quite a bit of current for a resistor. Consider this We will need at least a 1/2W resistor. If I were just making one or two copies of this circuit, and these were the only PNP power transistors I had on hand, I would try a larger value for R2, maybe approaching 1K.
In a production design, a better option would be finding a PNP power transistor with a higher gain so less base current would be required. The next step is to calculate the value for R1. PNP Transistor switching.