5 Steps for Choosing the Best RS232 to RS485 Converter

If you need to convert a serial RS232 signal to RS485 or vice versa then you need a RS232 to RS485 converter. Finding the best converter can be a challenge since there are so many different models, types and manufacturers. These 5 steps will help you make the right decision.

The Quick Checklist:

1. Preferred processor chip: Maxim or NI (very reliable)
2. Preferred supporting driver chip: Phillips, Maxim or NI (very reliable)
3. Minimum +/- 1.5V output voltage at RS485 side (ensures reliable data transmission)
4. Build-in electro-static protection for at least 600W (protects against static electricity)
5. LED lights for TX and RX activity (nice to have when troubleshooting)

1. Preferred processor chip: Maxim or NI
   This is the most important step. The reason why we highly recommend a RS232 to RS485 converter with a Maxim or National Instruments (NI) processor chip is because these are simply the best. We have extensive experience with these processors and time has shown us that these processor chips works with the majority of devices and equipment on the market. Very stable and east to use.


2. Preferred supporting serial driver chip: Phillips, Maxim or NI
   A RS232 to RS485 converter consists of several IC's, the main IC is the converter chip, another very important chip is called a Schmitt trigger, it controls the RS485 output signal. To ensure a good stable signal we recommend a RS232 to RS485 converter with a quality brand name Schmitt trigger from either Phillips, Maxim or NI.


3. Minimum +/- 1.5V output voltage at RS485 side
   We recommend a RS232 to RS485 converter with at least 1.5V power output for the RS485 TX/RX signals. This will ensure a strong communication signal and that your RS485 device gets sufficient power.


4. Build-in static protection to at least 600W
   Built-in static protection protects the RS232 to RS485 converter against high voltage spikes created either by static electricity or by surges in the supply voltage. This problem can exist both at the RS232 end and the RS485 end.


5. LED lights for TX and RX activity
   Not required but very nice to have. Being able to actually see when data is transmitted through the adapter is a big advantage when troubleshooting. This way its easier to find out where the problem lies; if its your computer, your device connected to the converter or the converter itself.

• Avoid converters with low-cost processors. These processors are usually poorly made Chinese products, incompatible with the serial standard, providing less than average signal charasteristics and noisy signal levels, resulting in broken or incompatible communication.
• Avoid converters with a low output power (less than 1.5V). Low output power makes the communication unreliable or even impossible.