mirror of
https://github.com/UtilitechAS/amsreader-firmware.git
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64 lines
2.4 KiB
Markdown
64 lines
2.4 KiB
Markdown
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# Overview
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This board can be used to simulate a M-Bus master device instead of
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connecting to the real AMS unit, i.e. usable for test and development.
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It takes a 5 V TTL level input (serial) signal and converts it
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to a M-bus level signal. It supports both sending and receiving.
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Inspired by [MBus_USB.pdf](https://github.com/rscada/libmbus/blob/master/hardware/MBus_USB.pdf)<sup>1</sup>,
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although significantly improved by using zener diodes so that it is
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flexible and can work with any external power source between
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21 and 42 Volt. Most DC-DC boost/step-up converter
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modules<sup>2</sup> should be fine for this.
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## BOM
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* 1 x zener diode [13V](https://www.elfadistrelec.no/en/zener-diode-017aa-13-on-semiconductor-1n5350bg/p/17006687) (note below)
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* 1 x zener diode [4.7V](https://www.elfadistrelec.no/en/zener-diode-do-35-500-mw-vishay-bzx55c4v7/p/30030851)
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* 1 x [BD136 transistor](https://www.elfadistrelec.no/en/power-transistor-to-126-pnp-45-no-brand-bd136-16/p/17130046) (most pnp bjt will probably work (with 40+ operating voltage))
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* 4 x [BC337 transistor](https://www.elfadistrelec.no/en/transistor-to-92-npn-45-800-ma-diotec-bc337-25bk/p/30012857) (probably any npn bjt will do (with 40+ operating voltage)
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* 1 x resistor 82 ohm
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* 1 x resistor 1k
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* 1 x resistor 8.2k (you can use 10k if power supply is well above 21V)
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* 5 x resistor 10k
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* 1 x resistor 220k
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* 4 x pin header 1x2
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Note for the 13V zener. This board design depends on the zener to
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operate below 1mA, e.g. like 1N5350 (figure 8) whereas a BZX55
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(figure 9) will maybe not operate properly.
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This limitation could be lifted by reducing the 8.2k resistor so that it
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draws enough current.
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## Schematic
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[SVG version](MBus_Simulator.schematic.svg?raw=true)
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## PCB
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[SVG version](MBus_Simulator.B.Cu.svg?raw=true)
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[SVG version](MBus_Simulator.F.Cu.svg?raw=true)
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## Version history
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Rev A - Only transmit. Wrong design, does not work.
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Rev B - Both transmit and receive. Should work (not tested yet).
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-------------
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<sup>1</sup>
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See also https://electronics.stackexchange.com/questions/99388/designing-a-m-bus-master-up-to-10-slaves/ and https://electronics.stackexchange.com/a/214477/568.
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<sup>2</sup>
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Like for instance [this one](http://hobbycomponents.com/power/698-xl60009-dc-dc-step-up-boost-converter) for £3.
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