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    sleep mode for PIC

    Hi I am using a PIC 18F4550 and want to put it into sleep mode to conserve battery life then wake it up using a 'wake up from interrupt' My question is what I need to do with the I/O lines? A basic sleep function will put the PIC into a mode which it consumes around 40uA. However, if other...
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    Thick or Thin Film Resistors

    Hi, I wanted to ask if I have a thick film resistor with the following specifications: Case size 0603 Tolerance +/-1% Voltage 50V Value 10K Temp coefficient 100PPM/C Application is for ultrasonic level measurement Can I replace this with a thin film resistor with a like to like spec? Or are...
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    General question regarding fuses

    Dear all, I have the following circuit 'A' -----------------| Fuse 315mA |----------------- Battery Positive + (3V) ---------------------------------------------------------------- Battery Negative - (0V) The battery is 3V. If I short out from point 'A' (fuse side) to...
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    2 x 16 lcd 4 bit mode

    hi all, I am using a pic to connect to a 2 x 16 lcd in 4 bit mode. I can get the cursor to blink on and off, also move to any position on line 1 or 2. however when I come to display character the screen goes blank. I am using a pic18f4550 and pic dem plus (microchip demo board). here is my...
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    Reaction Game

    Hi All, I need a bit if advise. I am designing a childs reaction game. there are 4 LEDS and push-button type switches. The LEDs will light uo randomly and the children will hit the key relating to the lit LED. This will be done with a PIC micro and written in C. What would be the best way...
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    Floating current source

    Hi all, I have the following circuit (see attached image). What would be the best way fro me to make the output a floating current source rather than with ground connection? Or use a current transformer? Note I am using currents of 100nA-300uA. Is this possible? Or could I use a photovoltaic...
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    Python Rs232

    Hi all, I am using python to control a digital multimeter through rs232. I have mages to send the Meyer commands from real term, so I can read the I'd number, read the software version, measure current etc. This works fine. I want to expand this so I can read and measure from the Meyer nut use...
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    long wires on digital signal

    Hi, I am driving a PWM circuit and low pass filter from a microcontroller. The output from this circuit will have a voltage in the range of 5-15mV. However there is a cable (twisted pair with overall screen) between the microcontroller and this PWM circuitry. The cable is around 12-18 inches...
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    micro I/o lines

    Hi all, I need to understand micro I/o lines for a PIC 18F. If I put a 10k pull up on a pin, and configure the pin as a input. It will read high. But if the same pin is set to an output, what happens? Also can I drive this low even though it has a pull up, by this I mean using the internal FET...
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    Making It High Impedance

    Hi all, I have a shift register 74hc595. This is driving a uln2003lv transistor array, that in turn drive relay coils. The shift register is controlled by a microcontroller. I need to make sure that the shift register is high z on switch on si I don't get relays coming on. From the truth table...
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    precision voltage regulator adjustable

    Hi all, I am looking to build a precision adjustable voltage regulator. I need to be able to control a voltage in the range of 5 to 10mV with great accuracy using a microcontroller. The other issue is that from the microcontroller I have a length of 2 core screened wire (around 500mm in length)...
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    Floating Dc Current Source

    Hi all, I was wondering if someone coulf help me, I am looking to build a floating current source (dc). this will be used to supply a current of between 1uA to 300uA. I was thinking of the best way to go about this,, perhaps an isolation amplifier or opto device. Any ideas? The current will...
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    Help With Circuit

    Hi all, i have attached the following circuit. it is basically a opamp driving a n channel fet used as a constant current source. the drain of the fet is connected to 0V, the source is at -5v. the gate is driven from the opamp output via 100R. my understanding that the opamp will drive the fet...
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    6 layer pcb stack

    Hi all, I have a coupe of questions: i have a 6 layer pcb, the stack up is as follows layer 1 - component (smd and through-hole) + tracking of analogue signals layer 2 - gnd layer 3 - inner track for digital signals i.e. spi, i2c layer 4- inner track for digital signals i.e. spi, i2c layer 5...
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    PIC Micro Output I/O

    Hi, I have a question regarding the PIC18F4520 micro. If i connect a 10K pull up to one of the pins and make this as an output. I believe that this will be a logic '1'. If i now make this (still as an output) but output a 0, how can the output be a 0 since it is connected to VCC via a 10K...
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    MOSFET to replace a relay

    Hi, I need to replace a relay with a MOSFET. The relays have very low contact rating is 30milli ohm. I need to switch low value resistors typically 0.2R. I am measuring currents in the 2uA range, so can't afford that to be affected. The relays are controlled from a PIC micro. Is there any...
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    A few questions on electronics

    Hi all, I have a few questions that I wonder if you could help me with. 1. If a electric MIC has an output impedance of 2.2K, does that mean anything I connect to it must have an input impedance greater than 2.2k? 2. I need the MIC output to be coupled then to an opamp, the value of the...
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    Piezo To Detect Sound

    Hi, I am considering a project where i can use a piezo buzzer to detect sound rather than using a mic. I have seen different types of piezo buzzers, some with 2 wires and some with 3 wire. I think that the 3 wire has an additional feedback signal. Not sure. Is this a possibility? I am trying to...
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    sound patterns

    Hi All, I was wondering if someone could help me. I have a requirement to detect different sound patterns that drive a piezo buzzer. The sound patterns differ for different types of alarm. This is an automated system which h can be left running and then it keeps a record of alarms that have...
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    Buzzer Help

    Hi, I have attached a copy of the voltge seen on a piezo buzzer. I need to ckamp this to 3V3 and then detect the edges of the waverform at 1.17 secs, feed this into a microcontroller and measure the time between pulses. I was thinking of clamping the wavefor which is 30V by using a suitable...
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