One of the more common questions I get asked is what size power supply is needed for.
Below is a list of common items and their approximate power requirements at 12v DC:-
*** Please remember that all values are approximate only ***
|Product Type||Power Supply|
|Drop bolts||up to 1amp|
|Prox readers||up to 100mA|
|Top hat piezo||110mA|
|DC Siren||up to 350mA|
|Bulldog dual screamer||max 500mA Strobe 150mA|
Dry contact, or relay contact this is a straight switch output, it has no voltage associated with it, the required voltage must be supplied to one side of the contact.
Open Collector this type of output switches to a reference voltage, most commonly it switches to negative. With this type of output the driven device (eg siren) is wired so that the negative side of the device is connected to the output, and the other side to permanent positive. These types of output are typically rated at 1Amp, 500mA, or 100mA.
Always allow 25% greater power supply capacity to cater for equipment variation and real.