4
RS-485
When used with RS-485 bus jumper J11 has to be set according to following picture.
Device needs 8..30 VDC power supply which is connected either with 1.3mm DC jack, with
positive center pole, or with terminal connections 1 (+) and 2 (-). DC-jack and terminal con-
nector is connected in parallel. Device is protected against the wrong polarity of power supply.
RS-485 can be easily added to computer using Nokeval DCS770 or DCS771 USB – RS-485 con-
verter or RCS770 USB/RS-232 – RS-485 converter. RS-485 is connected to terminal connections 3
(D1), 4 (D0) and 2 (Gnd). Wrong connection of polarity doesn’t harm the device.
Termination
Off
On
2-wire-485
Yes
No
Settings for jumper J7
If RS-485 bus master has ground connection available, then jumper called ”2-wire-485” has to be in
position ”No”. If master lacks the connection, then potential equalization has to be done via D1- data
line by putting the jumper to position ”Yes”.
Last device on bus should have termination jumper on. It makes AC-termination for the line, which
means that there is 1nF capacitance and 110 ohm resistance in series between the lines.
Maximum length for the bus is 1km, and it allows 32 devices, more devices can be connected by
using repeaters.
RS-232
When used with RS-232 bus jumper J11 has to be set according to following picture. Jumper J7 has
no effect when RS-232 is used.
Device needs 8..30 VDC power supply which is connected either with 1.3mm DC jack, with
positive center pole, or with terminal connections 1 (+) and 2 (-). DC-jack and terminal con-
nector is connected in parallel. Device is protected against wrong polarity of power supply.
RS-232 bus is not recommended because it is easily disturbed by EMI and maximum cable length
is only 15m in good conditions. RS-485 is recommended for longer ranges.
USB
FTR970 has also a USB connector but its use is not supported because USB connector cannot be
inserted through the cable gland.
