* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Analog-to-Digital Converter and Multivibrators
Electrical ballast wikipedia , lookup
Power inverter wikipedia , lookup
Immunity-aware programming wikipedia , lookup
Electrical substation wikipedia , lookup
Variable-frequency drive wikipedia , lookup
Current source wikipedia , lookup
Surge protector wikipedia , lookup
Alternating current wikipedia , lookup
Power MOSFET wikipedia , lookup
Stray voltage wikipedia , lookup
Pulse-width modulation wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Power electronics wikipedia , lookup
Voltage optimisation wikipedia , lookup
Voltage regulator wikipedia , lookup
Mains electricity wikipedia , lookup
Oscilloscope history wikipedia , lookup
Integrating ADC wikipedia , lookup
Analog-to-digital converter wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Opto-isolator wikipedia , lookup
Analog-to-Digital Converter and Multi-vibrators PHY 202 (Blum) 1 Simple Digital to Analog Converter V1 5V .111 corresponds to 7/8 J1 Key = A J2 Key = B 7/8 of 5 is 4.375 J3 Key = C R1 1.0k R2 2.0k R4 4.02k R3 4.02k + - PHY 202 (Blum) 4.377 V U1 DC 10M 2 Simple Digital to Analog Converter V1 5V .100 corresponds to 1/2 J1 Key = A J2 Key = B 1/2 of 5 is 2.5 J3 Key = C R1 1.0k R2 2.0k R4 4.02k R3 4.02k + - PHY 202 (Blum) 2.503 V U1 DC 10M 3 Analog-to-Digital • We have seen a simple digital-to-analog converter, now we consider the reverse process • For this purpose we introduce a new circuit element — the comparator • We have seen last semester a digital comparator, a logic circuit that determined whether the input word A is larger than the input word B • Now we look at an analog comparator, it determines whether voltage A is larger than voltage B PHY 202 (Blum) 4 PHY 202 (Blum) 5 Comparator (analog) U1 V1 3.1 V COMPARATOR_VIRTUAL V2 3V R1 1.0k + - 4.651 V U2 DC 10M + Input higher than – input, output is high PHY 202 (Blum) 6 Comparator (analog) U1 V1 2.9 V COMPARATOR_VIRTUAL V2 3V R1 1.0k + - 0.000 V U2 DC 10M + Input lower than – input, output is low PHY 202 (Blum) 7 1-bit analog-digital converter R1 1.0k V2 2.4 V V1 5V U1 COMPARATOR_VIRTUAL R2 1.0k Reference Voltage PHY 202 (Blum) Input voltage X1 2.5 V Input voltage is less than half of reference voltage, result is low. 8 1-bit analog-digital converter R1 1.0k V2 2.6 V V1 5V U1 COMPARATOR_VIRTUAL R2 1.0k Reference Voltage PHY 202 (Blum) Input voltage X1 2.5 V Input voltage is more than half of reference voltage, result is high. 9 Toward a 2-bit analog-digital converter R1 1.0k V2 4V V1 5V R2 1.0k U1 X1 2.5 V Greater than 3/4 COMPARATOR_VIRTUAL U2 X2 2.5 V Greater than 1/2 R4 1.0k COMPARATOR_VIRTUAL U3 X3 2.5 V Greater than 1/4 R5 1.0k PHY 202 (Blum) COMPARATOR_VIRTUAL 10 Toward a 2-bit analog-digital converter R1 1.0k V2 2.6 V V1 5V R2 1.0k U1 X1 2.5 V Greater than 3/4 COMPARATOR_VIRTUAL U2 X2 2.5 V Greater than 1/2 R4 1.0k COMPARATOR_VIRTUAL U3 X3 2.5 V Greater than 1/4 R5 1.0k PHY 202 (Blum) COMPARATOR_VIRTUAL 11 Toward a 2-bit analog-digital converter R1 1.0k V2 2.2 V V1 5V R2 1.0k U1 X1 2.5 V Greater than 3/4 COMPARATOR_VIRTUAL U2 X2 2.5 V Greater than 1/2 R4 1.0k COMPARATOR_VIRTUAL U3 X3 2.5 V Greater than 1/4 R5 1.0k PHY 202 (Blum) COMPARATOR_VIRTUAL 12 Toward a 2-bit analog-digital converter R1 1.0k V2 1.1 V V1 5V R2 1.0k U1 X1 2.5 V Greater than 3/4 COMPARATOR_VIRTUAL U2 X2 2.5 V Greater than 1/2 R4 1.0k COMPARATOR_VIRTUAL U3 X3 2.5 V Greater than 1/4 R5 1.0k PHY 202 (Blum) COMPARATOR_VIRTUAL 13 Finish this truth table >3/4 Comparator >1/2 Comparator >1/4 Comparator 0 0 0 0 0 1 0 1 0 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 ½’s place ¼’s place Doesn’t occur PHY 202 (Blum) 14 Integrated circuit version PHY 202 (Blum) Warning: may need to flip switch back and forth. 15 3.7 / 5 (in Scientific Mode) PHY 202 (Blum) 16 * PHY 202 (Blum) 2 x^y 8 = 17 Binary Mode PHY 202 (Blum) 18 Compare PHY 202 (Blum) 19 Scientific Mode PHY 202 (Blum) 20 Multi-vibrators http://www.ee.ed.ac.uk/~kap/Hard/555/node1.html PHY 202 (Blum) 21 Multi-vibrator • A multi-vibrator is an electronic circuit that can exist in a number of “states” (voltage and/or current outputs). • A flip-flop is a bi-stable multi-vibrator, bi-stable means it has two stable states. • A state is stable if it is robust against the fluctuations (noise) that are always occurring. PHY 202 (Blum) 22 Mono-stable multi-vibrator • A mono-stable multi-vibrator has one stable output (usually zero). • It also has an unstable state. Certain input will put the circuit into its unstable state, which lasts for a set length of time before returning to the stable state. – Unstable states are still robust to noise but do not last indefinitely long. • In wave terminology, this provides one with a single pulse. PHY 202 (Blum) 23 Pulse STABLE PHY 202 (Blum) UNSTABLE STABLE 24 One shots • One purpose of a mono-stable multi-vibrator is to output a signal of a specified duration. • The input (trigger) may be short (or unknown) in duration, but the output pulse has a predictable duration (can be controlled by the time constant of an RC circuit). – = RC – The time constant and duration are not equal but are proportional. • Such a circuit is called a “one shot.” PHY 202 (Blum) 25 Shapers • Another purpose of mono-stable multivibrators is to “shape” input signals. • Recall in digital circuits we want signals to be clearly high or low; a mono-stable multivibrator can take signals which are not of this form and create signals which are. PHY 202 (Blum) 26 Schmitt trigger PHY 202 (Blum) 27 Schmitt trigger • If the voltage is above a certain value (the upper trip point) and rising, the output is high. • If the voltage is below another value (the lower trip point) and falling, the output is low. • Otherwise, it remains whatever it was. PHY 202 (Blum) 28 Schmitt trigger The upper trip point Above the upper trip and going up The lower trip point PHY 202 (Blum) Below the lower trip and going down 29 A-stable multi-vibrator • In an a-stable multi-vibrator, there are typically two states, neither of which is stable. • The circuit repeatedly flips back and forth between the states. PHY 202 (Blum) 30 A-stable multi-vibrator J1 Key = Space R3 1.0k R2 10.0k XSC1 R1 1.0k R4 10.0k G T C1 A B C2 V1 5V 2.0uF Q2 BJT_NPN_VIRTUAL PHY 202 (Blum) 2.0uF Q1 BJT_NPN_VIRTUAL 31 A-stable Multi-vibrator • Assume a state where the transistor on left is ON and transistor on right is OFF and the capacitor on the left has no charge. • Since the left transistor is on (hard) it is not dropping much voltage, therefore “all” the voltage is being dropped by the resistors • The capacitor on the left begins to charge through the 10K resistor on the right PHY 202 (Blum) 32 A-stable Multi-vibrator PHY 202 (Blum) 33 A-stable Multi-vibrator Oscilloscope PHY 202 (Blum) 34 A-stable high low ON OFF Charge building up PHY 202 (Blum) 35 A-stable • Charge builds up on the left capacitor, “pullingup” the voltage presented to the base of the transistor on the right. • When the base reaches about 0.7v the transistor on the right turns on. • Current now starts to flow through the 1K resistor on the far right, thus dropping the voltage level at the collector. • That low voltage makes its way to the base of the transistor on the left turning it off. • The cycle repeats itself. PHY 202 (Blum) 36 A-stable low Turns off PHY 202 (Blum) ON 37 Duty cycle • In a square wave (e.g. a computer’s clock), the wave is characterized by its frequency, its amplitude and its duty cycle. • The duty cycle is the percent of time that the signal is high. • Duty cycle = thigh/(thigh+tlow)*100% PHY 202 (Blum) 38 Duty cycle example: thigh = 1.407 ms PHY 202 (Blum) 39 Duty cycle example: thigh + tlow = 2.111 ms Duty cycle = (1.407/2.111) = 66.65% PHY 202 (Blum) 40 555 Timer • A similar circuit uses the 555 chip (Integrated circuit) • The resistors and capacitors are external to the chip so that the period and duty cycle of the circuit can be controlled. PHY 202 (Blum) 41 555 PHY 202 (Blum) 42 555 as Monostable multivibrator PHY 202 (Blum) 43 555 as Astable Multivibrator PHY 202 (Blum) 44 555 Timer (WorkBench version) XSC1 R1 1.0k G T A 8 U1 VCC V1 5V C2 10nF PHY 202 (Blum) 4 RST 7 DIS 6 THR 2 TRI 5 CON OUT 3 B R2 1.0k C1 1.0uF GND 1 LM555CM 45 Crystals • The very high frequency square wave used for the CPU clocks are not generated in the manner described on the previous slides. • The high frequency signal is supplied by crystals subjected to an electric field. PHY 202 (Blum) 46 References • http://www.ee.ed.ac.uk/~kap/Hard/555/node 2.html#modes • http://en.wikipedia.org/wiki/555_timer_IC • http://www.kpsec.freeuk.com/555timer.htm PHY 202 (Blum) 47