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schematic

simulate this circuit – Schematic created using CircuitLab

Suppose I have a unipolar, differential 24V signal, and I want to step it down for use with a 5V differential receiver (such as RS-422), how can this be done?

Can I just use a voltage divider to step it down like above?

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  • \$\begingroup\$ An encoder powered off a 24V supply won't be outputting a 24V signal over its RS-422, any more your computer's USB port is sending a 120V signal just because your computer is powered off the 120VAC from the wall. Your question also doesn't make sense either since your 422 receiver won't work properly if it doesn't receive the compliment. The RS-422 is referencing using A and A' as the reference voltage to determine the signal logic level, not ground which will not be present if you do not connect both. \$\endgroup\$ – DKNguyen Oct 29 '19 at 17:35
  • \$\begingroup\$ I meant that if I was using a single ended encoder (without RS-422 receiver), I could just use an opto to step down the voltage. \$\endgroup\$ – 19172281 Oct 29 '19 at 17:43
  • \$\begingroup\$ What is the output current on the A and B lines? \$\endgroup\$ – Voltage Spike Oct 29 '19 at 17:58
  • \$\begingroup\$ You could use a resistive divider to step down each signal and feed it to two parallel wired oppositely comparators to produce X and X' to feed your 422 receiver. Or feed the resistive divider to a RS-422 transmitter. \$\endgroup\$ – DKNguyen Oct 29 '19 at 18:10
  • \$\begingroup\$ Why would I need use comparators? Couldn't I just use the voltage divider on each output leg of the encoder and feed straight into the 422 receiver? I've now realised that the encoder in question does output TTL level voltage, so only asking out of curiosity/to further learning \$\endgroup\$ – 19172281 Oct 29 '19 at 18:35

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