You must use both the A and B signal to have a quadrature output and to get X2 or X4 logic The fact that the signals are 90 degrees out of phase enables the controller to determine the direction that the encoder is spinning. It does not mean that the output will be 4 times the amount of the Pulses Per Revolution of the encoder. Quadrature output refers to the fact that the signals A and B are separated by 90 degrees of phase shift with A leading B or B leading A depending on the direction of rotation. The voltage should be measured across the output load to determine if the open collector is working properly. Therefore, if you were to measure the voltage at the output of an open collector that is not hooked up to some supply you would not see a change in voltage. A supply through a load must be connected to the output, otherwise the NPN transistor is simply creating a path to common, i.e. This means that a source is required for the output to work. It can be thought of as a switch that allows the circuit, after the load, to be connected to common. A NPN transistor allows the sinking of current to common. The Totem Pole is a 5V DC signal only, where the Push Pull will follow the input voltage.Īn Open Collector output is a NPN transistor. The other major difference is the output voltage between the two. The Totem Pole output is going to sink/source less current then a Push Pull output is capable of sinking or sourcing. The major difference between it and a Push Pull is the amount of current that it can sink or source. A Push Pull output is chosen when an Open Collector output will not work with the controller that is connected to the encoderĪ Totem Pole output is essentially the same as a Push Pull output however, it is the terminology commonly used when referring to a TTL device. This type of an output allows you to sink more current than a Totem Pole output and follow the input voltage. It can also help in increasing the distance in which a signal is transmitted.Ī Push Pull output is an output that allows you to connect either a sinking or sourcing circuit. A differential line driver will work both with a sinking or sourcing circuit. A differential line driver also allows you to sink or source more current then a Totem Pole output.
A differential line driver is used to help increase noise immunity. A differential output refers to the fact that each channel has a complement channel, i.e.
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