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tybro0103
tybro0103
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I'm currently working on a maglock door security system, and am using these same chips to transmit data from the RFID reader to an Arduino about 200ft away. I as well have had all kinds of problems with these annoying, but awesome :), chips. I'm not sure I'm operating at 100% fool-proof yet, but here's a few things I've found out:

• There's a tradeoff between transfer rate and susceptibility to EMI. The MAX485 has a high transfer rate, but is very influenced by EMI. Try the MAX483. Same chip with slower transfer rate, but very little EMI.

• In some cases, such as with a long cable distance, I've found it to work better without any terminating resistor...don't ask me why. :)

• Make sure both DE and RE pins are connected to either ground or +5v volts+5V. They aren't required to be connected depending on whether you're in transmit or receive mode, but I could swear I've had better results when neither of them are left floating.

I'm currently working on a maglock door security system, and am using these same chips to transmit data from the RFID reader to an Arduino about 200ft away. I as well have had all kinds of problems with these annoying, but awesome :), chips. I'm not sure I'm operating at 100% fool-proof yet, but here's a few things I've found out:

• There's a tradeoff between transfer rate and susceptibility to EMI. The MAX485 has a high transfer rate, but is very influenced by EMI. Try the MAX483. Same chip with slower transfer rate, but very little EMI.

• In some cases, such as with a long cable distance, I've found it to work better without any terminating resistor...don't ask me why. :)

• Make sure both DE and RE pins are connected to either ground or +5v volts. They aren't required to be connected depending on whether you're in transmit or receive mode, but I could swear I've had better results when neither of them are left floating.

I'm currently working on a maglock door security system, and am using these same chips to transmit data from the RFID reader to an Arduino about 200ft away. I as well have had all kinds of problems with these annoying, but awesome :), chips. I'm not sure I'm operating at 100% fool-proof yet, but here's a few things I've found out:

• There's a tradeoff between transfer rate and susceptibility to EMI. The MAX485 has a high transfer rate, but is very influenced by EMI. Try the MAX483. Same chip with slower transfer rate, but very little EMI.

• In some cases, such as with a long cable distance, I've found it to work better without any terminating resistor...don't ask me why. :)

• Make sure both DE and RE pins are connected to either ground or +5V. They aren't required to be connected depending on whether you're in transmit or receive mode, but I could swear I've had better results when neither of them are left floating.

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tybro0103
tybro0103
  • 241
  • 2
  • 3
  • 7

I'm currently working on a maglock door security system, and am using these same chips to transmit data from the RFID reader to an Arduino about 200ft away. I as well have had all kinds of problems with these annoying, but awesome :), chips. I'm not sure I'm operating at 100% fool-proof yet, but here's a few things I've found out:

• There's a tradeoff between transfer rate and susceptibility to EMI. The MAX485 has a high transfer rate, but is very influenced by EMI. Try the MAX483. Same chip with slower transfer rate, but very little EMI.

• In some cases, such as with a long cable distance, I've found it to work better without any terminating resistor...don't ask me why. :)

• Make sure both DE and RE pins are connected to either ground or +5v volts. They aren't required to be connected depending on whether you're in transmit or receive mode, but I could swear I've had better results when neither of them are left floating.