Do you also struggle reading your own and others huge ladder diagrams? The truth is, that even though ladder diagram (LD) is an easy programming language for. Here is the circuit diagram of a simple stepper motor controller using only elementary parts. The driver circuit uses, four transistor (SL100) to drive the motor. Bidirectional Counters. As well as counting “up” from zero and increasing or incrementing to some preset value, it is sometimes necessary to count “down” from. Yi Yao - Oscilloscope. Yi Yao > Projects > Oscilloscope. Project started on 2. Project completed on 2. First of all, many thanks to Professor Iravani for teaching us the analysis of linear systems, Professor Wang for her patient tour of digital logic and Verilog. To all the lab TA's for tips on debugging circuits and practical insights. Rundle for introducing me to C/C++ and of course, Mr. There were many motivating factors. My experience with oscilloscopes began with an old analog machine in the . I just remember how tedious it was to get the thing to show a trace. And then to trigger properly. Project started on 2005-12-21. Project completed on 2006-01-14. First of all, many thanks to Professor Iravani for teaching us the analysis of linear.Upon comparing the results with known values, I realised that the oscilloscope was off vertically and horizontally (i. And the probes were so oxidized. One couldn't quite understand why it wouldn't work. But there was excitement when the darn thing finally worked and you could see the Lissajous curves or the capacitor charging and discharging. And then, there was these awesome shiny new digital oscilloscopes in the electrical engineering and physics labs at University of Toronto. They even had an auto set function. I mean, how cool is that? Document Number: 38-08032 Rev. The Z80 CPU is an 8-bit based microprocessor. It was introduced by Zilog in 1976 as the startup company's first product. The Z80 was conceived by Federico Faggin in. Digital logic circuits important question and answers for 5 units 1. 1 Digital Logic Circuits. In the previous Asynchronous binary counter tutorial, we saw that the output of one counter stage is connected directly to the clock input of the. You didn't have to fiddle with the knobs anymore, it just worked. I immediately knew what I wanted for Christmas or my birthday. ![]() Looking in the Allied Electronics and Newark in One catalogues, I found out that that was out of question. The Agilent 5. 46. D 1. 00. MHz mixed signal scope. Starting from $5. USD. So my natural instinct is to build one if I can't afford one. And thats what I spent my Winter holidays doing. Requirement Specs. These were the preliminary requirements that I set out to fulfill: 1 channel (or 2 channels with common ground). It seemed hard to have 2 channels working in electrical isolation. Digital. I don't have a CRT or know how to control one. Communicate to a computer / Palm Pilot via RS2. For easy debugging and display, a computer is fast and easy to program. Also allows for future interface with Palm Pilots and easy porting to other systems. Accuracy of 1m. V+5. V to - 5. V input range. Ampilifcation circuit have relatively high cut off frequency (4. KHz suggested). Relatively high compared to the 4k. Hz (nyquist frequency of 8ksps)Explanation. For those of you who are new to this stuff, here's what the requirement specs mean. The number of channels which an oscilloscope has is the number of signals which it can be viewed at the same time. I hope you know what digital and analog means. For the purpose of this project, digital signals can be communicated with computers while analog signals can't. RS2. 32 is the name given to your serial port. At the back of your computer, there's many ports where you can plug things into. The RS2. 32 port has 9 pins and looks like: RS2. At the heart of most digital oscilloscopes is a device (usually a chip of some sort) which converts analog voltage levels to digital signals. This chip is called an analog to digital converter (ADC). If this happens very quickly and the computer keeps track of voltage over time, a plot can be drawn, hence the principal of a digtal oscilloscope. How quickly the chip is able to make these conversions is called the sampling frequency. It is given in units of ksps (kilo- samples per second) or Msps (mega- samples per second). And if you know the sampling frequency to be f, the highest frequency sine wave it can detect is f/2. This is known as the nyquist frequency. Any higher than that and all you'll get erroneous results and an effect known as aliasing (click here for details). For my case, I chose ADC0. Supremetroncis. This chip is guarenteed to work at 8ksps. And hence, the nyquist frequency is 4k. Hz. That means, the fastest sine wave I can see with chip is 4k. Hz before bad things start happening. Most oscilloscopes have some analog circuit which will amplify and shift the trace before it is sampled by the ADC. By shifting the signal before amplifying it gives better accuracy in many cases (avoid saturation with amplifiers). As with all analog circuits, they will work only within a range of frequencies. After a specific frequency, the cut off frequency, the output voltage level is less than 7. It would be preferrable for this frequency to be much higher than the nyquist frequency of the ADC. So, now that we know what we're looking for, here's the design. Design. While I had some knowledge of electronics hardware, I still do not understand all components fully. It is very different to sketch an opamp circuit on paper than it is to choose the correct components and lay it out to minimize noise. So, there's bound to be oversights where a resistor value was too low or the components were not well chosen, etc. Hence the difference between physics where it supposed to work and engineering were good approximations and correct components are key. I'm still learning so please contact me with comments and suggestions. The design of this oscilloscope was simple. It is summarized with the following diagram. Flow diagram for the digital oscilloscope. Vertical Shift and Amplifier. The purpose of these modules is to condition the signal appropriately for the ADC to read. The ADC can convert voltages within the range of 0 to 5. V. By setting the vertical offset and amplification, one can . A suitable equation relating the input voltage (Vin), vertical offset (Vs), amplification (A) and the output voltage to the ADC (Vadc) can be: which would allow for the maximum of 1. V input range (A=1, Vs=0, Vin=- 5. V to +5. V). Also, this scope must have accuracy of 1m. V. The typical screen size on a Palm Pilot is 1. X1. 60 pixels. Hence a 1. X1. 00 pixel window with 1. X1. 0 grid would be suitable for showing the trace which leaves enough space to display system information. This means, the smallest range this oscilloscope should be able to capture is within a 0. V (=1. 00px X 1m. V/px) range. It would also be nice to have variable gain inbetween these two ranges as well. The following table lists the magnifications posible. Circuit parameters. Volts per Div(m. V)Measurable Window(V)Amplification Needed(X)Feedback Resistor (see circuit, Rf)(k. This was done by cascading a series of buffers, differential amplifiers and summing amplifiers. The result was: Click on image for higher resolution schematic. Originally, 1. 0k resistors were chosen for most of the circuit since resistors with values in multiples of 1. This would be useful for the variable gain circuit. However, Supremetronics ran out of them and I was out of luck. So 2. 0k were used instead. I salvaged a few 1. Due to the sensitive nature of this project, all resistors had 1% tolerance. The opamp chosen was the LF3. It has high bandwidth of 4. MHz, input impedance of 1. Each package contained 4 opamps which saved space and came at an economic price. I'm sure that was not the best reason to pick this opamp, but it still worked. The variable gain amplifier must be able to accomodate 7 distinct amplification levels. This meant, Rf could be 7 independant values. This was accomplished by using a 4. IC which was not shown on the schematic. Based on the input to the IC, Rf could be configured to choose any of the 1. Since 7 resistors were used, only 7 channels were used and 3 of the 4 lines were needed to address each channel. Wiring diagram to create Rf from a 4. Looking at the circuit, you may notice that there is a physical input signal called Vso which was not mentioned in the design equaiton. This voltage is generated by an R- 2. R resistor network driven by a CMOS buffer. Hence its voltage range is between 0 and 5. V. The logical vertical offset (Vs) can be calculated using Vs=5- 2. Vso. However, doing a full circuit analysis will reveal that the the design equation still holds. R- 2. R networks are constructed using resistors. They are a type of DAC (digital to analog converter). They can convert a digital signal into an analog voltage level. Say an n bit unsigned integer was to represent a voltage level, Vout, between 0 and Vcc. An R- 2. R resistor network could be constructed to do this as the following: General R- 2. R network. Every resistor labeled R must all have the same arbitrary resistance. Every resistor labeled 2. R must have twice that resistance. For a CMOS circuit, a logical high is Vcc, usually 5. V and a logical low is 0. V. Doing a circuit analysis, one will find that Vout can be described as: where Di is 1 or 0 and Vcc is the supply voltage to the CMOS driver. Most CMOS buffers are capable of outputing a maximum of 2. A. So, resistor value for R must be chosen in the k. This circuit fails miserably if one were to use TTL gates as the voltage levels for high and low have too wide a range. I once read a 2. 2. V for a logical low out of a 7. LS0. 4 (NOT gate). So, you must use CMOS outputs to drive this circuit. The most precise resistors have tolerance of 1%, so excessive number of bits may not guarentee such precision, but the voltage levels will always be ascending if the input values are consecutively ascending. The requirements demand 1m. V accuracy over a 1. V range. Doing the calculations, it was found that the size of the output integer needs to be 1. This seems some what inconvenient, so it was rounded up to 1. Power Supply. Like all electrical circuits, this one needs electricity to work. The opamps need a positive and negative voltage source to work. The precision of these two voltages must be very precise and symetric otherwise, the virtual ground would be off (different from the real ground) and this would introduce significant amount of error in the final signal. For this project, I used a modified ATX power supply. The one in my computer was getting noisy so I replaced it with a new one although the old one was still functional. ATX power supplies can output +1. V, +5. V, +3. 3. V, - 5. V, - 1. 2V relative to common ground. So, instead of spending a lot of money on a lab power supply, I used an ATX power supply instead. Modified ATX power supply. But measuring the +1. V and - 1. 2V, I found out that the power supply was not so precise.
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