I found in an old documentation a circuit that uses old components, but its characteristics show that it can be activated with the signals from the outputs of a microcontroller. Is there any danger in mixing old and modern technologies in a case like this?
If the input characteristics of the circuit are the same as those obtained at the output of a microcontroller, there is no danger. Eventually, the circuits may be powered by different voltages, in which case sources of appropriate voltages should always be used having a common ground. The possibility that the circuit to be coupled to the microcontroller must also be checked is not noisy to the point of requiring a special decoupling so that it does not interfere with its operation.
