Level Shifter

In order to connect the open-collector output of a standard Conrad DCF receiver module (order number 121177), which has a relatively low operating voltage of 1.5–15 V and an NPN open-collector output, to a PLC requiring a positive-switching 24-V signal at around 150 mA, level shifting is necessary. This can be achieved in a simple manner using a miniature relay connected between the positive supply voltage for the module and the DCF module output, as shown in Figure 1. In this case the current load on the DCF output must not exceed 1 mA.