I would like to design a system that works with my ESC/POS thermal printer that activates a siren when a receipt is printed. My thermal printer has an RJ12 port which is intended to connect to a cash register. I can send an ESC/POS command that kicks open the cash register by sending it a pulse through this port (I believe it is ~24V at very low current). My only requirement is that the siren be very loud (for use in a warehouse setting). I am not sure if the pulse itself can drive a siren, or if I am going to have to construct a circuit that is activated by the pulse. I would like to build the simplest and cheapest circuit that I can, but I don't really know how where to start, any guidance would be greatly appreciated!
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I know that setup very well, and yes, you have to use an external power supply for your siren. Simply connect a 24V DC relay coil to one of the channels on that RJ12 port. – Janka Aug 24 '17 at 17:53
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Are you going to buy a simple and cheap siren? – Andy aka Aug 24 '17 at 18:51
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@Andyaka I'm only familiar with tiny DC buzzers with two leads. Will using a large DC buzzer (externally powered) with a relay coil between printer and the buzzer be enough? could you recommend a specific siren? – 00728M Aug 24 '17 at 18:58
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@Janka Would the cash register kick pulse be considered an AC signal? do I need to use a relay with AC input? or would the single pulse be act like a very short DC signal? – 00728M Aug 24 '17 at 21:03
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It's not AC, it's 24V DC, and the pulse is a single "click", not some buzz. Those small buzzers have an internal oscillator. You have to connect the coil between the output pin (2,5) and the +24V pin (4) of the connector. GND (6) is for the input (3) only. The TMT88 manual says both outputs may sink up to 1A (only one at a time) but I wouldn't trust that for "compatible" printers. – Janka Aug 25 '17 at 00:34