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    Interfacing arduino mega 2560 to 3v circuitry

    Hi all, I am using an Arduino Mega 2560. This is to be connected to some circuitry which runs off 3V. I have seen the following TXB0108 level translator. However it seems to me that it is a 3V to 5V translator. Where i need 5V to 3V. Can anyone help?
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    Pic interface with sensor

    Hi, I have attached a datasheet for a sensor that i am looking to interface to a PIC. Looking at the timing diagram. Is it possie to use pwm + low pass filter to generate the 0.65VDC? Or is there a better method. Could i use a timer to pulse this pwm output line high for 0.1ms, then on the high...
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    Phototransistor

    Hi, I am testing the circuit below. My understanding is that light controls the current from the base to emitter, which controls the collector current. I am powering from 3V. I see a change of 0.2V (when it is dark)to around 2.8V at the output (light conditions). I am trying to understand the...
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    Pickit3 or icd3 programmers

    Hi all, Is there anyway to make the PICKit3 or ICD3 as gang programmers? Mostly programming PIC18F family under MPLAB. Is there any information available to understand the process of prigrammung i.e. VPP, Clock and data signals etc. Thanks in advance.
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    Wanted: Student Manual Art of Electronics

    Hi all, I am after a book: Student Manual - Art of Electronics I have seen it on Scribd. But does anyone have a copy of this that they want to sell or a PDF copy? Thanks.
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    A/D impedance PIC connected to RC circuit

    Hi all, I have a RC circuit in parallel 330K and 1uF. This is going to be connected to an A/D input of a PIC. The PIC is a 16LF1936, which says the impedance is 10K source. 1. How do i calculate the impedance of the RC circuit? I think it is Z=squareroot of RxR + Xc x XC. XC is the reactance...
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    Wavelength and matching components.

    Hi all, I was trying to find the difference of wavelength of 868MHz compared to 928MHz. Using a online calculator i found that the wavelength if 868MHz is 34.5cm and 928MHz is 33cm. If i wanted to use a printed antenna, would i simply make the length of the track 33cm? What hapoens to matching...
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    4 x 7 segment common anode

    Hi I have a 4 x 7 segment common anode display, which i will be driving from a PIC micro. I need some help in calculating resistor values and selecting the correct PNP transistors. Can anyone help? Thanks in advance.
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    Need a 1.8V supply

    Hi, What is the best way to achieve a 1.8V supply? Can this be done with transistors only? I have 3V3 input need 5mA output. Thanks.
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    Reset pin of PIC

    Hi, I have a reset pin of a PIC micro connected to 5V via a 10K pull up resistor. If i connect a I/O line of a second PIC to the reset of the first PIC. Can i reset the PIC by outputting a zero? Or should it be a logic 1? Thanks
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    Controlling reset of PIC using transistor switch

    Hi all, I am using a PIC18F4520. I need to be able to control the reset/MCLR line (which at the moment is pulled up via a 10K resistor to VDD 3.3V). I need the control to be software driven rather than have a switch from the pull up to 0V. What would be the best way to do this? Could a Logic...
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    PIC I/O lines when configured as input or output

    Hi, I am trying to understand what happens 'internally' (on a hardware level) to a PIC I/O line when it is configured as an input / output or high impedance. I know that there are N and P channel FETs which are set accordingly when the port is set i.e. to sink or source current. I need a better...
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    Frequency generator

    Hi i am after a schematic for a frequency/waveform generator. Adjusable frequency and amplitude for sine, square and ramp. Upto 100KHz. Something which is easy to build. Any ideas?
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    Protecting I/O lines of microcontroller

    Hi all I am using a PIC which is connected via a 3 way connector. The connections are from PORTB of the PIC. PIC is powered from 3V. I want to know what is the best way to protect the I/O lines of the PIC in case the user accidently applies too much voltage on the connector end. Could i use a...
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    LED forward voltage and brightness

    Hi I wanted to ask a question on LEDs. If i have a 3V3 supply and using a LED of 2.1V forward voltage and IF of 20mA.the mcd is 200. I tend not to run st full 20mA but give some head room so 15mA is what i normally use. To calculate the required resistor is R = 3V3-2.1V/15mA How is this...
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    Capacitance on PIC I/O line

    Hi I wanted to ask a question regarding capacitance on the input of a PIC I/O line. Why is this undesirable? Is it because if we get a voltage rising quickly then we will get a sharp rise in current due to the capacitance? Hence we must keep try and keep the capacitance as a low value? Also...
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    Analogue Electronics Practical Experiments

    Hi all, I am trying to get better at analogue electronics. My main issue is that i cannot read what is going on in a circuit. I am currently reading a Basic Electronics book to understand some theory work. I also need to be building some circuits practically. Can anyone recommend a good simple...
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    Calculating current limit resistor value

    Hi I have a 33R resistor and a 39pF cap to 0V. Note: First it is the 39pF connected the PIC I/O then to 0V. The 33R is then from the capacitor to a 3 pin header. The 33R is connected to the TX line of a PIC. I think the PIC can sink or source upto 25mA. If the output of the TX line was VIH ie...
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    2 layer and 4 layer pcb

    Hi all I am starting to get familar with schematic capture using Eagle PCB. I am now ready to do some simple pcb designs. I am looking st a 7 segment pcb as a starting project. This fits into a microchip development board that i have. So it will be a small module pcb. The bosrd will plig into...
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    Understanding N channel and P Channel FETs

    Hi all I have always had difficulty in understanding how FETs work. N channel and P channel also all the variants such as enhancement and depletion types. Also the operation modes ie. Linear mode triode mode etc I would like to learn this practically. Are there any good resources where i could...
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