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Hjelmslund Electronics   Tinghøjvej 15 - 2860 Søborg - Denmark        Phone : +45 5150 4986        Mail :

2 Jan 2023 : Good news - we are back in business again, currently building up a stock of the devices we haven't been able to deliver for such long time.
More details here.
RS485 converter for industrial use

Our USB to RS485 converters

Hjelmslund Electronics are specialized in making USB to RS485, RS422 and RS232 converters, targeting customers who needs converters with better quality than the cheaper non-isolated, but smaller and less expensive than the industrial types of isolated converters.

All converters are usb powered, and works as virtual comports. 
flag Dublin, Ireland 
Very satisfied with the service and product supplied by Hjelmslund. Very fast response time, even when we required a special assembly. High quality product, worked excellently first time.

John Clarke - Nines Engineering
Website :

USB to RS485 isolated converter series - USB485

The USB485 family of USB to RS485 converters installs as virtual comports, and can be accessed just like a standard comport in the PC. They are powered from the USB side, hence no external power supply is needed. They are fully Modbus compatible, and both 2 wire (half duplex) and 4 wire (full duplex) models are available. They support baudrates up to 1 Mbps, and have 128 bytes transmit and 256 bytes receive fifo.
Last but not least, all models are electrically isolated, as any high-quality converter should be!

USB RS485 converter

2 wire half duplex rs485 converter: USB485-STIXL

USB485-STIXL : Isolated USB to RS485 converter

A classic 2 wire, half duplex model, that meets most customers demands. Its 2500 Volt isolation barrier and ESD protection gives it the quality needed, for being used in industrial automation.

During operation it automatically switches between transmit and receive mode, without any need for the user to control the data direction programmatically by asserting RTS, as seen in simpler converters.

PDF Icon  USB485-STIXL product sheet

Shopping Buy USB485-STIXL Online [EUR 80 @1]

USB to RS422converter - isolated

4 wire full duplex rs485 / rs422 converter: USB485-STI4W

USB485-STI4W : Isolated USB RS485/422 converter

The STI4W is our 4 wire full duplex RS485/422 converter.
The receiver is always enabled, but the transmitter is only enabled during data transmission, thus making it possible to use it even as a slave device.

* RS422 users : The STI4W fullfill both RS422 and RS485 specifications.

PDF Icon  USB485-STI4W product sheet

Shopping Buy USB485-STI4W online [EUR 85 @1]

USB virtual com port

Isolated RS485 panel mount converter: USB485-ILP

USB485-ILP : Panel mount RS485 converter, isolated

Mount it as any other port in your enclosure, with the USB connection outside and the RS485 cable inside.

By placing your isolation barrier in the cabinet wall, you avoid getting USB cables into your industrial installation, as well as avoiding having industrial communication near your pc, hence maintaining the best possible system separation.
Isolated, 2 wire, half duplex

PDF Icon  USB485-ILP product sheet

Shopping Buy USB485-ILP online [EUR 85 @1]

USB RS485 ccable

USB RS485 converter with cable endings: USB485-CPT

USB485-CPT : Isolated RS485 converter with cable endings

The CPT is our 2 wire, half duplex, cable version converter.
3 meter highly flexible cable, but other lengths available upon request.


Green : Data +
Brown : Data -
White : Gnd

PDF Icon  USB485-CPT product sheet

Shopping Buy USB485-CPT online [EUR 90 @1]

RS485 cable modbus

RS485 with cable and RJ45 - for Modbus: USB485-MB45

USB485-MB45 : Isolated RS485 converter for Modbus

The RJ45 connector is wired according to the Modbus specifications Ver 1.02   Section 3.5.1

Pin 4 : Data -
Pin 5 : Data +
Pin 8 : Common

The cable screen is connected to Modbus 'common' internally in the converter. Standard cable length is 3 meter, but 1.5 & 5 meter cable are also available.

PDF Icon  USB485-MB45 product sheet

Shopping Buy USB485-MB45 online [From EUR 89 @1]

IO products - serial port controlled

USB driven IO system

USB powered 2 channel digital IO system: USB-I2O2

USB-I2O2 : Comport controlled 2 channel IO system

The USB-I2O2 have 2 opto isolated inputs and 2 relay outputs, and is programmed as a serial port, using the handshake signals to set and read the IOs.
No special drivers are needed, just program it using the standard windows component mscomm32.ocx in your application.

Opto coupler inputs  :   3-48Vin, AC and DC.
Relay outputs  :   250Vac / 3A SPST - normally open

PDF Icon  USB-I2O2 product sheet

Shopping Buy USB-I2O2 online [EUR 110 @1]

USB to RS232 isolated converter series - USB232

Our isolated USB to RS232 converters are ideal for connecting PCs with industrial installations, maintaining a high quality electrically separation between the 2 systems.
They installs as virtual comports and can be accessed just like any other comports in the PC. The converters are USB powered and need no external powersupply.
All our RS232 converters support baudrates up to 1 Mbps, and includes 128 bytes transmit and 256 bytes receive buffers.

USB RS232 converter

Isolated RS232 converter: USB232-STISO

USB232-STISO : Isolated USB to RS232 converter

Size doesn't matter, sometimes does!
The smallest isolated RS232 converter on the market, so if you want compactness, this should be your choise.

Compact - USB powered - easy to use

- Height : 14mm
- Width : 23mm
- Length : 66mm

PDF Icon  USB232-STISO product sheet

Shopping Buy USB232-STISO online [EUR 65 @1]

RS485 com port - panel mount

Isolated RS232 panel mount converter: USB232-ILP

USB232-ILP : Panel mount USB to RS232 converter

The USB232-ILP is an isolated RS232 converter for through hole (25mm diameter) mounting in cabinet walls, for giving easy access to internal RS232 devices, thru an external USB connection.

The converter have a 2.5 KVolt isolation barrier and 15KV ESD protection, hence enough robust for being used in industrial installations.

PDF Icon  USB232-ILP product sheet pdf

Shopping Buy USB232-ILP online [EUR 72 @1]

USB RS232 converter

RS232 converter with handshakes : USB232-DTHISO

USB232-DTHISO : Isolated USB to RS232 converter

Desktop version RS232 converter with full handshake. It has clearly marked which signals are inputs and which are outputs, so no doubts and no more googling before hooking up your RS232 devices - no more problems!

It is USB powered, consuming less than 100mA, so it can be powered from any USB port and hub flawlessly.

PDF Icon  USB232-DTHISO product sheet

Shopping Buy USB232-DTHISO online [EUR 103 @1]

USB isolator series - USBISO

USB isolator and transient protection for USB 2.0 full speed systems. No powersupply and no drivers required.
The isolators are intended to be used in industrial environments, where the host computer needs to be isolated and protected from external electrical interference, and where groundloops needs to be eliminated.
The USBISO-AA is a little stick type and the USBISO-DT15 is a larger desktop type, with extended isolation voltage.

USB isolator

USB isolator with extended isolation voltage: USBISO-DT15

USBISO-DT15 : Desktop type isolator for USB 2.0 systems

Brief specs.
- 2.500 Volt rms isolation
- IEC 61000-4-2 Level 4 ESD Protection
- Can deliver 200mA to the external USB device
- Height : 29mm
- Width : 64mm
- Length : 89mm

PDF Icon  USBISO-DT15 product sheet

Shopping Buy USBISO-DT15 online [EUR 88 @1]

USB isolator and repeater

USB isolator and protection device: USBISO-AA

USBISO-AA : Stick type isolator for USB 2.0 systems

Youtube Icon    Video review of USBISO-AA

Brief specs.
- 1.000 Volt DC isolation
- IEC 61000-4-2 Level 4 ESD Protection
- Can deliver 200mA to the external USB device
- Height : 14mm
- Width : 23mm
- Length : 66mm

PDF Icon  USBISO-AA product sheet

Shopping Buy USBISO-AA online [EUR 72 @1]

Hjelmslund Electronics   Tinghøjvej 15 - 2860 Søborg - Denmark        Phone : +45 5150 4986        Mail :
Updated 3. June 2023