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    Inductor Coil Testing

    Hi all, I have a transponder coil 7..2mH and 125KHz resonant freq. The transponder has been tested with a LCR bridge meter. I need to design a circuit to test that is fr is at 125KHz. How can I do this? Would I need a LC parallel circuit and feed with freq generator at 125KHz? Any help would...
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    32kHz clock

    Hi all, I wanted to ask a few questions regarding measuring a clock frequency of 32.768kHz. This is connected to a PIC micro with capacitors (15pF) to each side of the crystal, other side to gnd. Also have a series 0R resistor in the xtal in pin. 1. Capacitance probe will cause loading, so...
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    32kHz crystal

    Hi, I have noticed that a 32kHz crystal has malfunctioned i.e. not oscillating, it is cracked, what could cause this to happen? Thanks
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    LC circuit Mutual Coupling

    Hi all, I have a LC tank circuit connected to a base of a NPN transistor via a 10K resistor. The emitter is tied to 0V. The collector has a 10K load resistor tied to 5V. The LC circuit has a resonance of 100KHz. I want to mutually couple this circuit so that the transistor is switched. How...
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    OptoMOS Relay

    Hi, I am looking at an alternative Opto MOSRelay, used for electronic switching - 12V supplies. Both are SOP4 packages, with the same pinout. The comparison has shown the following: 1. The new part has faster turn on / off times i.e. on - 1ms, off - 0.5ms compared with the older relay i.e. on...
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    Car Key Transponder

    Hi all, I have attached a circuit diagram from a car key transponder emulator that my friend has. I believe these work by putting the key emulator in an energised electromagnetic field, the inductor from the field mutually couples to the LC tank circuit (as in the diagram). I am not too familiar...
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    Crystal clock and USB operation

    Hi all, I am using a PIC18F4520 microcontroller to use USB. I wanted to ask how the what crystal value I need to operate the USB at 480Mbits/s and 5Gbits/s. Is there a simple calculation that can help me? Thanks in advance
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    USB differential pair using Saturn PCB

    Hi all, I am currently looking to use USB 2.0 (480Mbps speed) on a design. The USB differential signal coming in from a USB connector to a PIC microcontroller. I have tried using Saturn to give me a 90 Ohm differential impedance (see below), I am using FR4 PCB and 1oz copper (i.e. 18um copper +...
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    Power Electronics for Beginners

    Hi all, I am looking to re train in the field of electric vehicle technology. Alot of what I see is based on DCDC topolgies, inverters, SMPS design etc. Could anyine recommend a course (online) or a good book that can help me to understand this subject area? Thanks in advance
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    Tektronix 2336 scope no horizontal trace

    Hi all, I havea Tektronix 2336 scope, this gas a fault, it does not show any traces. Is this easy to repair? Are there potentially any dangerous voltages present even after switching off the mains and opening it up. Thanks in advance.
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    Transimpedance v integrating amplifier

    Hi, I have attached a diagram of a photodiode connected to an opamp, this is an I to V converter or transimpedance amplifier, the current from the photodiode is converted into voltage by the feedback resistor. I have also seen the same can be achieved using a capacitor in the feedback instead...
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    Piezo buzzer operation

    Hi all, I have attached a diagram showing a 3 wire piezobuzzer connected to a micro. I am not sure how this works. I think you apply a voltage between the main and ground terminals. The feedback is then used to keep the buzzer oscillating around its resonant freq. I am not sure how the...
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    Electric Vehicle Technology

    Hi all, Can anyone recommend a good book that explains the technologies used in Electric Vehicles for beginners? Thanks in advance. PS: I have looked at various websites but need a book.
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    Power Electronics for Beginners

    Hi all, I am looking for some recommendations please. I am looking for a good book on power electronics for complete beginners. One that does not go to heavy into maths. I am looking for a change in career and getting into electronics for electric vehicles. I am a electronics technician but do...
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    SPI Signal Overshoot (to WIFI chip)

    Hi all, I have been monitoring some SPI signals for a WiFi IC. The device is powered from 3.3V. The CLK frequency is 4.5MHz However, I am seeing overshoot and undershoot on the CLK, MISO etc For example on the CLK the overshoot can get to 3.9V. The undershoot is about -0.65V. This could cause...
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    Double functionality on Micro

    Hi all, I have a issue where due to lack of i/o lines i need to double up on one i/o line. As an A/D to read light sensor and output to drive the LED. The light sensor output should go from 0 to 2.7V. However, it is being clamped to around 2V (forward volt drop of LED) i think it may be due to...
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    PIC A/D

    Hi, I have a 2.2uF cap and 330K resistor in parallel going into the A/D channel of the PIC at the emitter of a phototransistor.The Top part of the circuit is part of a light sensor. The PIC has a 10 bit A/D. However I am not seeing a full scale of 0V to 2.8V. Note. Using VDD (3.3V) as VREF for...
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    Active high signal

    Hi all, I have an active high signal on an IC. This puts the IC into shut down mode. It is connected to an I/O line of a PIC. Can i connect the shut down pin to OV via a 10K pull down resistor, this makes the IC active. Then output a logic 1 from the PIC to enable shut down i.e. making it high...
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    RF basics

    Hi, I am new to rf design. I have been given a project that uses a 868MHz rf chip. Are there any good sites for beginners with minimum maths? Also what is carrier frequency, frequency deviation, preamble. Lastly, how does crystal selection select the frequency i.e..868MHz? Thanks in advance
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    Protection of Lithium Batteries

    Hi all, I am looking to parallel a few Lithium Coin Cell Batteries i.e. CR20332. Could I put in Schottky diodes in replace of the PMOS FETS in the image attached? Or will I not need to use anything as the batteries are not Lithium Polymer type? Best regards, Raj
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