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Driving inductive loads

 

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In experimental photography with light barriers it often happens that inductive loads, such as magnetic valves, lifting- or pulling magnets, relays, etc. have to be driven.

With its four outputs, the light barrier system Joker² is predestined for applications like that. Using the outputs cameras, speedlites and also inductive loads can be actuated. However, especially with the latter, a few things must be carefully considered.

Each of the four outputs of the light barrier system Joker² has two “switches“, one for “measurement“ and one for “release“. Each switch consists of a transistor in open-drain circuit, which can carry a nominal current of 300 mA or 500 mA for one second.

Note for non-electricians: Using a transistor as power switch, the current can only flow in one direction, which is different to a meachanical switch, where the current can be carried in both directions.

An inductive load can be connected to each output of the light barrier system Joker².

Schalten von induktiven Lasten

Please connect the inductive load, as shown in the circuit diagram  (klick for download), to a 2.5 mm stereo jack plug. The power supply may be a power adaptor with the required output voltage and power (in the circuit diagram the two poles are depicted as +U and -U).
Important note: The flyback diode is mandatory! If it is missing, high induction voltages (several hundreds of volts) may destroy the output while switching off the load! Please pay attention to the polarity of the diode.

If the power consumption of your load amounts to less than 300 mA, it will be sufficient to only connect it to the contact for the release. The contact for measurement remains unconnected. If required one can also link a second load to the contact for measurement. Like this two devices can be operated at one output simultaneously. However, in case of a higher power consumption, both contacts must, as depicted in the circuit diagram, be wired parallel.

 

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