Nine Things I would Do If I might Start Again RS485 Standard > 자유게시판

Der SRF485 verfügt über einen integrierten 5-V-Leistungsregler, der von 8 V DC bis 14 V DC geregelt werden kann. Sowohl Strom- als auch RS485-Signale werden dem Modul über einen 10-Pin-IDC-Stecker zugeführt, wodurch die Verkabelung einer großen Anzahl von Modulen sehr einfach ist. Die Reichweite des SRF485 beträgt 30 cm bis 5 Meter. Der SRF485 Sensor verwendet den RS485-Standard für die Kommunikation mit bis zu 127 Modulen. Der SRF485 ist ein Ultraschall-Entfernungsmesser mit einem einzigen Schallkopf, der auf dem SRF02-Design basiert. It can also emulate analog voltage outputs from a variety of other vacuum transducers. Pull-up/Pull-down resistors (Idle-line failsafe) at one end of the 485 bus may be used to bring the line voltage to a steady state (200mV) value at the end of a transmission; when all drivers are in the passive state. The SMINI card is designed so that each input line is wired from the external hardware directly into the appropriate pin on input buffers U3-U5. For example, using QuickBASIC with my Pentium in data acquisition, I read input bytes 200,000 times per second. Read more about RS422. Read more about RS232.

It is also possible to convert between RS485 and RS232 using simple interface converters that may include optical isolation between the two circuits as well as surge suppression for any electrical 'spikes' that may be picked up. EIA-485 devices may be used in 422 circuits, but EIA-422 may not be used in 485 circuits (because of the lack of an Enable line). •Balanced line drivers with tristate capability. In addition to this, RS485 extends the common mode range for both drivers and receivers in the "tri-state" mode and with power off. A user slot and connection to the processor and power is available for custom interfaces that cannot be handled by the standard hardware set. The vast majority of C/MRI outputs make use of standard current-sinking, where the transistor switch, built within every C/MRI output line, completes a connection to ground to activate the connected railroad device. Industrial Ethernet and the "conventional" Ethernet both share the same physical and MAC levels , but use different protocols. This would enable the same standards to be used worldwide and also give manufacturers access to a global market using just one product. High Speed Ethernet or HSE and the "conventional" Ethernet both share the same physical and MAC levels , but use different protocols.

It is intended for United States, non-military government use. A DIP IC socket can be used to allow easy IC replacement to use different speed/feature parts or to replace damaged parts. Either a 4 position terminal block (5mm pitch) or RJ45 connectors can be fitted for the RS-485 connectors. RS485 RS-485 is a standard that allows high speed data transmission along with multiple transmitters and receivers and this makes it able to be incorporated as a network solution. The PCB-CB485 is a bare PCB to build the CB485 logic-level to RS-485 adapter. With the 1x10 male header option, the CB485 can be used with solderless breadboards. This means that there can be 32 nodes capable to both transmit and receive. In addition there are 2 index inputs. The current-sinking design is more tolerant of driving heavier loads since the ground traces are wider and there are three ground pins per I/O card. Thus, if you are not currently interested in implementing input line filtering, simply skip ahead to SMINI Parts. Adding a low-pass RC (Resistor-Capacitor) filter to each input line is easy with SMINI. The maximum capacitor that fits on the card is 470µF, 10Vdc (Digi-Key P6217) which when combined with the 100Ω resistor produces a filter time constant of .047 seconds (calculated as .000470 x 100) or 47ms, and a cut-off frequency of 3.4Hz. This means that the noise would have to hold the input in the incorrect state for approximately 47ms before the software would receive an incorrect input.

The product of the resistor and capacitor values (i.e. R x C), is called the filter time constant. The R and C combination is called a low-pass filter because it lets DC and low-frequency signals pass through with practically zero attenuation while attenuating high-frequency signals. I have discovered a nice CLI tool called mbpoll than can be used for fast Modbus wiring validation via CLI. In place of using hardware filtering, you can perform software filtering in your application program. The larger is this constant the greater is the filtering. Its advantage is that extra hardware is not required and it is easy to vary the effective filter time constant. Adding a noise filter to each input line can reduce the effects of this noise. The RS485 line driver has an additional "enable" signal which is used to connect and disconnect the driver to its output terminal. Their maximum current draw, corresponding to displaying a yellow aspect with red and green both turned on, is only about .03A per signal.

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