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Recent content by dougy83

  1. D

    Comms over DC power cable

    Thanks again. I have simulated the simple differential AM transmission and reception, using a couple of LC filters, amplifier, a peak detector and bit-slicer comparator. Seems to work alright across a wide enough range of input level and temperature. A 455kHz resonator should be able to be...
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    Comms over DC power cable

    Thanks aliarifat794. I've seen that IC, but it's quite expensive, and not too easy to source. Thanks Ron. I was expecting more noise on my supply cable, but the devices are actually quite clean in that regard, so it might be fine without a specialised IC. What scheme were you using that slowed...
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    Comms over DC power cable

    Hi all, Does anyone know of a low part count and cheap solution for bidirectional (half-duplex) communications on the 48VDC supply line? Baud rate of 19200bps would be nice. I did a quick test with an LM567 @300kHz, but it is slow and unreliable. Also, it requires a very high SNR of -6dB...
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    pic24fj breakout

    Thanks for the responses, and for having a look at the circuit. The device is not recognised by the programmer, so the config bits don't yet have a chance of causing issues. The PK3 works fine for a pic16f677 I have on hand. I'm guessing it's most likely a soldering issue, or as Nigel mentioned...
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    pic24fj breakout

    I made some simple breakout boards for pic24fj256ga705 a while back, but never managed to have the pickit3 recognise a device on any of the boards. Does anyone have any experience with this processor family? The VCAP is actually a 10uF/50V X7R, and has ~1.8V across it. The datasheet is quite...
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    Sine to square wave conversion

    Now set the input frequency to <50Hz. You have formed a schmitt-trigger oscillator.
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    Sine to square wave conversion

    Those two schematics shown above (posts #4 and #6) are not reliable. The first (#4) is a high-gain amplifier, that will amplify any noise on the input if used with non-schmitt-trigger inverter, and will oscillate if used with schmitt-trigger inverter (when the input signal frequency becomes...
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    Using the B-E junction of a transistor as a diode

    The VBE of 2n3906 is <5V; this may be an issue for you. If you don't mind it acting as a low voltage zener diode, then you may be OK. Also, I believe the base and collector are often connected together for the diode function, to reduce the base current.
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    2D parts tracer

    These magnetic encoders have more steps per rotation: https://www.ebay.com.au/itm/194625197361 Another way to "trace" the outline would be to use a camera below a translucent table to capture the silhouette, and then run a simple threshold and contour function.
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    Cheap RF modules.

    Well, that would make more sense. It could be tuned without special equipment by maximising the amplitude of the analog output (the input to the bit-slicer opamp), while the transmitter is pulsed. If the tuning-by-antenna-length statement were true, then the receiver selectivity is garbage.
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    Cheap RF modules.

    Some of the sellers of the cheap receivers claim to receive both 315 and 433MHz; the tuning is "selected" with the antenna length.
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    power supply

    The schematic seems to be showing it going to 100V. The split inductor allows a higher voltage than the MC34063 could handle on its switch/collector pin. If you want to just use an off-the-shelf inductor, you'll want to use an external switch (FET/BJT transistor) that can handle the 100V. You...
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    power supply

    The schematic you attached generates the 10V-100V supply, depending on the switch setting. To make your own supply, the normal way would be to use a SMPS IC and wire up something similar to that in the schematic. Alternately, you could get the microcontroller to drive a transistor/inductor/diode...
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    Need advice on powering LED and can't say what it is because of patent pending

    If you can't get a PIR module that will operate directly off the battery, then you can use a DC-DC converter, e.g. a inductor-based boost converter, or a switched-capacitor/charge pump. The QX23xx series look alright; they don't need many support components, are cheap, small, and have low...
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    Sorensen PTM12-10.5

    That looks better! Thanks for sharing; hopefully it will help someone.
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