L102 S ABB Alarm System - modification to add a 2nd signal adapter with separate p12Vdc psu.

Above alarm system has 1×anti-tamper channel and 2×alarm signal channels. A flashing red signal light needs to be retro-fitted to the system. Maximum output voltage per signal channel is 12Vdc @ max. 300mA. Anti tamper from flashing light needs connecting in serial with currently fitted anti-tamper device - NOTE:- named resistance is 2.7K ohms....needs checking! Idea:- switch in a secondary PSU to power flashing light 'WITHOUT' sourcing current from alarm system. Add a green 'OK' led 1.5Vdc @5mA. Method:- Alarm activates signal channel which activates a NPN transistor which in turn switches on a relay at 5Vdc @12mA. Relay switches 12Vdc to newly installed flashing light rated at 12Vdc @ max. 300mA. At the 'OFF' setting, afore mentioned green 'OK' led can optionally be retro-fitted to the system. Due to discrepancies in the values of components (transistor, resistors and relay), a 12K trim-pot has been fitted to the NPN base to adjust relay voltage. Circuit is currently proof of concept (albeit in a virtual simulation environment) - it has not been built (as yet) in the real world. Wednesday 17th May 2017 @ 2047HRS. Note:- I created this wee 'ditty' for a mate of mine who is an Alarm systems specialist. Feedback from him and many thanks from his Boss resulted in a slab of fine English Ale being slid in my direction...which was nice! This circuit has now been built and retrofitted to over half a dozen local systems....was offered a job too, but explaind that building Guitar Amps/Studio equipment has more of a 'hard-on' factor than installing flashing lights and 'beep-beep' systems.

published 8 years ago