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    Diode Characteristic Graph

    Hi, I have a question on my course which is: 1) FIGURE 3 (on page 7) shows a PIR (passive infra-red) detector and its associated amplifier, as used in burglar alarm systems1. a. The detector is powered from a 12 V unregulated supply that needs to be stepped down to 5 V. Design a...
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    First order filter help

    Hi, I have the following question: FIGURE 2 shows the response of a first-order filter to a step input. Estimate the half-power cut-off frequency of the filter and sketch its frequency and phase response. My attempt at the answer is: The half-power cut-off frequency is when the voltage is at...
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    Sallen and Key Bandpass filter

    Hi, I have the following question, which I need some fundamental help with to get going: Design and PSPICE model a bandpass filter of ‘Sallen and Key’ topology and having the following characteristics: fo ~ 3.3kHz, Q ~2.2. Verify your design by means of a Bode plot. From my learning material...
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    Op-Amp Gain

    I have a question in which I have to compare the specs of two op-amps in a table to text descriptions and match them together. My question is, one of the descriptions states that the gain is 112dB. I believe this to be Op Amp A, as the description also states the PSRR is 120dB. How do I...
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    Op amp max frequency based upon slew rate and gain

    Hi, I have the following question in my HND... Estimate the maximum frequency of a sinusoidal input signal of 10 mV peak, for distortion-free output, when applied to an op-amp circuit of closed-loop gain of 100. I have searched all through my course material, online for ages and have only...
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    Calculating an single output from two inputs...maths help!

    Hi, I have an application where I am using two devices: 1) Absolute Encoder 2) Inclinometer What I am doing is measuring the angle of a device in a single plane. My device is a pivoting arm which can move left/right and up/down. However, due to the mechanical setup, when the arm moves left...
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    Graph/Error correcting - maths formula NOT homework

    Hi, I hope this is in the right part of the forum. I'm working on a problem at the moment where I am measuring an angle across 180 degrees using an inclinometer, however for my application I consider this -90 to 0 to +90. From working out the mechanical position of my inclinometer, I am going...
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    Nyquist and data logging

    Hi, I'm not sure if this is the correct forum, but couldn't see where else to post. I'm looking at a datalogging application where I am measuring the force acting upon something due to sea waves. Due to the mechanical setup, my numbers will only be positive. I am trying to research optimum...
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    Optical Bonding Issues using UV agent

    Hi, I have a product which is essentially a handheld device with a small screen in, to be exact... a LS027B7DH01 Sharp 2.7” 400 x 240 Transflective LCD. This is then bonded to a clear plastic window using Novachem Optimax 6435 adhesive. The adhesive is cured using a UV light, a high power...
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    Best place to buy used electronics?

    Hi, Can anyone recommend a good place to buy used electronics equipment such as power supplies? Specifically I am after a dual quadrant power supply for testing of electronic charging circuits in our device. The cheapest one I can find brand new is the Rohde & Schwarz HM8143 on RS...
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    CO2 cannister valve

    Hi, I am working on a project where I need to activate CO2 coming out of a small canister, like this, does anybody know of a valve which could be used and electrically activated? thanks,
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    Battery life calculation.

    Hi, Please can someone help me with calculating how much battery capacity I need. Calculating different ways which all seem logical in some respects, I can get very different answers! What I have is: - A datalogger which takes a sample 3 times a minute. - The sample time is ~1sec and draws...
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    4-20mA splitter

    Hi, I need to make a simple 4-20mA splitter to mount on a small PCB. It needs to accept a 4-20mA input, and then provide 2x 4-20mA outputs which are a mimic of the input. I have a 24VDC power supply and no current limitations. The logic to me seems like I would need to amplify my current...
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    R/2R resistor ladder

    Hi, I have a question in my HND about R/2R ladders, I have been given the diagram below and asked the following question: The diagram of FIGURE 1 shows a 3 input R/2R digital to analogue converter circuit. By working back from the output (or otherwise) to find the equivalent input resistance...
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    Boolean Logic check

    Hi, Could somebody please confirm for me that I have my assignment answers correct? The boolean expression is at the right hand side at the final gate. Thanks thanks
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    Counter module/input

    Hi, I am working on a small project at home where I want a count down module. Either analogue or digital input, don't mind too much at the moment. But what I want to do is be able to input a length of time in hours, the timer to count down, and then use this timer value going into an MSP430...
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    Successive approximation ADC

    Hi, I am doing an HND in instrumentation and control engineering, I have the following question to which I can find nothing in my teaching material even relating to it!! I have searched online and read a bit about SAR ADCs but cannot find how to do this... The full range of a 12bit...
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    mv to ma current amplifier design

    Hi, I am currently working on a instrumentation amplifier design to accept mV inputs and provide a 4-20mA output. It is to be used with various industrial sensors like load cells (load is in tonnes/kg not voltage). The problem I am facing is that I do not know for sure what instrumentation...
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    MSP430 or similar serial input

    Hi, I want to build a small data logger which can accept either an RS232 or RS485 input. I want to use a uC rather than buy an existing datalogger and build up a circuit myself. Before I even look into the data logging side. Can anyone point me in the right direct on how to get a serial...
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    Solar charging.

    Hi, I am just starting to look into turning a product I have into wireless version which solar charging. I was hoping someone could help me with the basics of charging which I haven't looked into much before. My circuit requires 205mA max at 12VDC. I have a 12VDC SLA battery with a 14Ah...
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