Notes on the selection of incremental rotary encoder
With regard to power supply and encoder and PLC connections: the general incremental encoder has three kinds of working power: 5Vdc, 5-12 Vdc or 5-26Vdc. If you buy the encoder with 5-26Vdc, you can use PLC 24V power supply, the need to pay attention to is:
1. Encoder consumes current in the PLC power supply range.
2.As the encoder parallel output, connected to PLC I/O, the need to understand the signal level of encoder is push-pull type (or push-pull output) or open collector output, such as open collector output, N and P two, and PLC I/O the same polarity. There is no problem with the push pull output connection
3. Encoder, such as the driver output, the general signal level is 5V, the connection should be careful not to let the power level of the 24V into the 5V signal wiring to damage the encoder signal.
Three aspects should be paid attention to:
1. Mechanical installation dimensions, including the location of the mouth, shaft diameter, installation hole; cable outlet mode; installation space volume; work environment protection level to meet the requirements.
2.Resolution, that is, the number of pulses per lap when the encoder is working, whether to meet the design requirements. The number from 6 to 5400 or higher, the more the number of pulses, the higher the resolution; this is one of the important basis for selection.
3.Electrical interface, the encoder output common push-pull output (F HTL format), voltage output (E), open collector (C, common C for NPN type tube output, C2 output for the type PNP), long line driver output. The output mode should match the interface circuit of the control system. The incremental encoder usually has three signal output (difference six signal):A, B and Z, with TTL level, A pulse before and after B in A, B pulse, the pulse is 90 degrees, each ring sends a Z pulse, can be used as reference for mechanical zero. General use of A ahead of B or B ultrasound A before the judge. The use of PLC data acquisition, the use of high-speed counter module; the use of industrial computer data acquisition, the use of high speed counting board; the use of single-chip data acquisition, it is recommended to choose the input port with a photoelectric coupler.
4. B pulse is recommended to do forward (forward) pulse, A pulse to do the reverse (backward) pulse, Z origin zero pulse.
5. Set up counting stack in electronic device.