Question

My teltonika RUT 955 is configured the following way (picture attached) to trigger the DC OC output from the gui and It works perfectly fine. Got the connection idea from https://wiki.teltonika-networks.com/view/RUT955_Relay_to_Open_Collector_Output .

My Question:

What is the role of connecting pin no 4 to the power supply? what exaclty does it do? My from my understanding it doesnt play a role in completing the circuit as just connecting 3 and 8 completes the circuit. Any info regarding this is appreciated. Thanks !!!

Answer 1

Hello,

To be more clear I'd like you to look at the picture below, as it shows some approximation of internal details. Since internal circuitry voltage levels are lower than the actual allowed maximum voltage by the transistor, it has to be supplied from the external source. Actual values may differ, but, for example, a 5V signal from the integrated circuit applied to the base of the transistor can drive the load, for example a relay, which requires 12V supply. The idea is that transistor in open collector configuration works as a switch. When no base voltage is applied its state is off. In order to have the drive capacity, there needs to be a voltage drop upon its terminals, thus, the need for Pin 4 as a stable reference and pin 3 for output state control.

Best regards,

Comments

Hey !! Thanks for your answer! Do you mean that the base voltage provided by the teltonika is not enough and an external voltage must be applied to the base for the transistor to work ? Thanks !

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What I meant was that internal voltage, supplied to the transistor, would not be sufficient to drive heavier loads.