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USB/RS-485 interfaces converter
USB/RS-485 interfaces converter (hereinafter referred to as a “converter”) is intended for mutual conversion of USB and RS-485 interfaces signals. Main application field of the converter is connection of controllers, measuring devices, data collection systems and etc. to computers which are not equipped with bit serial interfaces. The converter serves for autonomous configuration of one or several devices equipped with RS-485 interface. Support of USB 2.0 along with previous versions of USB specification enables to connect the converter to any computer which has a free USB. Supply package includes a CD with drivers suitable for Window OS.
Device description and working principle:
USB/RS-485 interface converter (view Pic. 1. Appearance of USB/RS-485 converter) is designed in a compact plastic housing (1) targeted at direct connection to a USB port without additional cables. USB connector is located at the end of the housing (2). Cable for connecting devices via RS-485 interface is at the opposite side.
Before starting to work with USB-RS-485 converter, a relevant driver from the CD with software must be installed. Driver is also available via this link at ElMetro-Engineering LLC official website.
Assignment of the converter contacts (view Pic. 2. Assignment of USB/RS-485 converter contacts):
- Red terminal – “A” line of RS-485 interface;
- Black terminal - “B” line of RS-485 interface.
Direction of data transmission from PC to a device and backward is switched automatically. When a low level signal is sent, the converter switches on in data transmission mode (А-В < -0.2 V). In case a high level signal is sent, the converter switches on for a while until there is a high level signal at the output (А-В > 0.2 V). Further maintenance of this level is ensured by internal pull-up resistors. The rest of time the converter works in data reception mode.
Connection circuit of secondary devices into RS-485 network by means of the converter is shown in Pic. 3. Connection circuit of USB/RS-485 converter.
A typical circuit is provided above. A certain type of circuit is determined by the following factors:
- Type of the network devices;
- Relative position of the devices;
- Network length;
- Inter-earth voltages between the nodes;
- Each converter is galvanically isolated.
Standard connection circuits are designed for connecting maximum 32 devices via USB/RS-485 converter.
Galvanic isolation of the interface provided in the devices makes the connection easier. In quite long networks with significant inter-earth voltages between the nodes correct interconnections are essential (shield grounding). Besides that 120 Ohm terminators should be applied at the ends of the line in long networks.
Technical characteristics and advantages:
The converter has the following technical characteristics and advantages:
- Power supply could be provided via USB port of PC.
- Up to 32 devices could be connected.
- Support of USB 2.0 protocol (full speed), compatible with USB 1.1 and USB 1.0.
- Data transmission rate: up to 250 kbit/s.
- Automatic detection of data transmission direction.
- Compact design.
- Galvanic isolation: 500 V.
- Ambient temperature range: -40...+85 ºС.
Supply package:
- standard supply package: converter (1 pc.); CD with software (1 pc.); product certificate/manual instruction (1 pc.).
Application:
The converter is widely used for mutual conversion of RS-485-USB signals and connection of flowmeters, videographic recorders, input and output models, controllers and other equipment of ElMetro-Engineering LLC production to a PC.
Customers’ feedbacks:
To view customers’ feedbacks on products of ElMetro company, please, follow the link.
To make enquiry and get a commercial offer on USB/RS-485 converters of the Russian manufacturer ElMetro company, please, send us product order code (view page 66 of full catalogue) to e-mail: info@elmetro.ru or contact us via tel.: +7 (351) 220-06-01. To discuss technical questions, please, refer to technical support tel.: +7 (351) 220-06-03.