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* I232 Communication Components for RS232 *
* Electrical Isolation, Fast Data Transfer, and Long Cables. *

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* I232 Communication Components for RS232 to RS232 *
* HAAS, FANUC, & Other CNC Machine Users *

The Betatronics® I232B-2 Isolator High Baud Rate Extender System is a low cost means to simultaneously increase your distance between RS232 ports, increase transmission speed at long distances, and greatly reduce problems from noise and damaging electrical faults.

Key Features of the Betatronics® I232B-2 System:

  • High baud rates at long cable length saves time and therefore money. Up to 4000 ft @ 115.2 kbaud and 8000 ft @ 19.2 kbaud is usually feasible. Doubling the baud rate cuts data transfer time in half, etc.

  • Do you need 4000 to 8000 feet? Probably not, but you will get outstanding performance at shorter distances.

  • CNC program verification is made easier with high baud rates because the program can be sent back to the source computer for comparison. This is one of the best ways to know what is in the CNC is what was sent.

  • The isolated Betatronics I232 greatly reduces the risks of data errors and equipment damage that exist with non-isolated RS232 data communication circuits. Discussed below in "Why is a DIRECT RS232 to RS232 connection risky"?.

  • The Betatronics I232 with dielectric isolation between input and output greatly reduces problems from lightning storms, electrical faults, and ground currents.

    It is very difficult to solve data error and equipment damage problems simply thru machine grounding, becasue it only takes about 3 volts of noise to cause data errors and somewhat above 25 volts to damage components.

  • The I232 is optically coupled to electrically isolate RS232 equipment from each other, and from faults on the interconnect wiring. This electrical isolation is how electrical damage and data errors are reduced.

  • The enclosure is Delrin with four mounting holes. This provides long over the surface voltage breakdown paths.

  • Quick easy installation with modular connectors ( RJ12, telephone type; and RJ45, network type ). You can use standard pre-assembled CAT 5E network cable, or make your own.

  • The Betatronics I232 Isolator is a low cost high value product.

Important Questions:

  • What do slow data transfer rates cost you?

  • What are your downtime and repair costs if an RS232 circuit fails?


The I232 System consists of:

   -- RS232 cable (2 ft) -- I232 isolator -- long interconnect cable -- 2nd I232 -- 2nd RS232 cable (2 ft).

To see a block diagram LEFT CLICK HERE

Same block diagram except rotated 90 to allow printing LEFT CLICK HERE

The low cost I232 System uses optical couplers to electrically separate RS232 circuits from the interconnect cable, yet communicate data at high data rates. The isolator integrated circuit used in the I232B-2 has an isolation voltage rating of 1260 v rms ( 1780 v peak ) for 1 minute, and is tested at 1520 v rms ( 2150 v peak ) for 1 second.

The RS232 side of I232 requires +12 vdc (9 to 12 is ok), this may be supplied from inside the CNC, computer, or a "wall" transformer. Power for the interconnect side is generated internally and isolated.

Generally RS232 integrated circuits have a maximum input rating of +/- 25 v. However, data errors may occur with a ground voltage difference of 3 v or less between the two ends of a directly connected RS232 communication path.

The following experiment with the I232 System shows its immunity to common mode noise. A 1000 v rms 60 Hz signal was applied between the the RS232 equipment common (ground) and a copper wire in the interconnect cable between two I232 boxes. Whether the signal was present or not had no effect on the data, and no equipment damage. Note 1000 v rms equals 1400 volts peak. This is approximately 460 times larger than the 3 volts that may cause data errors in a directly connected RS232 system. This is a severe test. If you had a direct RS232 connection all sorts of electronic components would have been destroyed as well as data errors from this test signal. The cost would be very high. In a plant environment 480 v rms would be the most likely maximum fault voltage.

By using high quality low capacitance CAT 5E cable and low impedance drivers we obtain long cable length capability at high baud rates. Our long cable capability is much greater than an RS232 direct connection. In a directly connected RS232 link maximun cable length is about 6 feet at 115.2 kbaud compared to 4000 feet or more with our I232. The maximum length is a function of baud rate, cable attenuation, and your environment.

Modular connectors make installation easy with readily available CAT 5E network cables which come pre-terminated with standard RJ45 connectors.

If you need to route to several machines, one at a time, then there are manual switch boxes for RJ45 connectors, usually 4 positions. A 12 position box is available. Otherwise it is easy to change machine connection by use of an inline CAT 5E coupler.

The I232B-2 has only one TxD and one RxD channel. Thus, you must use XON/XOFF or Xmodem protocol for handshaking. If you want hardware handshake, then the cost is higher.

Because we only transfer the data signals from one location to another with no intermeadiate processing you can use any suitable software you choose and connect to any RS232 machine.

The I232B-2 is in a Delrin plastic box that connects by a 2 foot cable to your your RS232 connector. This allows for mechanically secure mounting of the I232 without a strain on your RS232 connector. Also reduces vibration problems with the interconnect cable. If special wiring or connector is required, then it is just a matter of changing the cable. The dimensions are 3.5 x 1.9 x 1 with a bolt pattern of 3.125 x 1.5 with four 3/16 holes. Accepts #8 screw. See photo.

An I232B-2 box is required at each RS232 connection point. This provides protection for all your RS232 devices and allows long cable lengths that are not possible with direct RS232 connection.

The I232 System is a point to point communication system and not a network system. However, it is possible to put a manual switch box in the CAT 5E cable. This has no effect on the maximum cable length from one point to another. Thus, you can do the same things with the I232B-2 Isolator as you can with a direct RS232 connection, but at longer distances and higher baud rates.

A Case History --- Direct RS232 Data Error Problem.

The cause of this problem is electrical noise generated by the CNC machine.

This is a discussion about a customer that has a CNC Vertical Mill that it was impossible to send or receive data via a direct RS232 connection from a central computer to said CNC without data errors. This was not baud rate or distance dependent.

Communication to an adjacent, almost identical but older, machine is and was not a major problem. The communication parameters for the problem CNC were 9600 baud, 7 data bits, 1 stop bit, even parity, and XON/XOFF handshake. The cable shield was connected to pin 1 at both ends. Pin 7, signal common, was connected via a separate wire in the cable at both ends. Pins 2, 3, and 7 are used for data, 4 and 5 were jumpered locally at each end, and separately so were 6, 8, and 20. The non-problem machine was setup identically.

Interchanging the cables between the two machines left the problem on the same machine. Thus, it appears the problem was a machine problem.

When the serviceman from the machine supplier tested communication with his laptop there was no problem. Both the machine vendor and the central RS232 system supplier claimed it was the other's fault. The CNC machine works fine except for this RS232 problem when directly connected to the central computer.

The open space between these two machines is about four feet. Power and ground are obtained from an overhead bus duct. Each machine has its own supplementary 8' ground rod. The two rods are about 9' apart. Each machine has a shielded RS232 cable about 120 feet long from the central computer to the CNC, cable is similar to Belden 8723.

The problem machine has brushless servos, while the non-problem machine has DC servos. The problem did not exist with the servos off. But obviously one can not do DNC (direct numerical control) with the servos off. This has been an on going problem for a number of years.

Just resting, garbage data was received at the central computer. Note communication failed in both directions.

In the last month I got involved in the problem. With a Fluke model 87 DVM in AC mode I measured about 4.5 volts difference between the enclosures of the said two machines, and about 0.5 volts in DC. The peak voltage is clearly larger than 4.5 volts. I did not have a scope with me and therefore could not look at the signal. This is a large enough signal to cause RS232 errors.

As I have previously pointed out, in general, I do not believe that ground rods do much for noise problems.

I installed our I232 isolator system with about 130 feet of unshielded CAT-5E cable and the problem was eliminated. This totally breaks the DC ground path between the two RS232 ports. Further I increased the baud rate from 9600 to 115,200, a 12 times increase, and there were no communication errors. We transferred four or five several megabyte files in both directions with no errors.

Many problems can be solved by changing from a direct RS232 connection to an isolated connection.

Fairly clearly the problem machine was the source of noise, but this machine works fine in all other respects, and therefore the vendor was somewhat correct in saying the machine was ok. The real problem was the need for a method to prevent ground loop noise from interfering with the RS232 signal path. The noise source could have been something external like a welder, or high ground loop currents from a ground fault in a totally unrelated system.

In our own shop voltage measurements in AC mode are about 1.5 v between machines and we do not use any ground rods at the machines. Everything is referenced to the ground rod at our central circuit breaker box. In our shop all machine RS232 circuits are isolated with our E232 Ethernet to RS232 units. Our safety ground wires are #6 or #8 and 50 to 100 feet long.

Grounding Problems go to

Why is a DIRECT RS232 to RS232 connection risky? go to

Call 734-930-6136 for a quote and technical information.

The approximate cost for one RS-232 to RS-232 System that has an isolator at each end, standard 9 pin or 25 pin connections to computer and CNC, and 150 ft of interconnect cable is about $275 plus shipping and handling.


PO Box 1288, Ann Arbor, MIchigan 48106-1288
voice 734-930-6136
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