Home built 60's style FACP project (Suggestions Welcome) - Page 1
Forum section: electronics / projects

author: WyverntekGameRepairs
author_rank: Regular Contributor
timestamp: May 08, 2025, 01:07:25 am
content: Long time no see! Been a minute since I last visited this place. Thought I would hop on and post a new project I began recently.I collect old commercial fire alarm related stuff and particularly like the older analog electromechanical systems from the 50's, 60's, and 70's, so I decided to try to build my own panel and design it after those old analog relay logic designs (but with some modern improvements, of course). The idea is that it will be compatible with a wide range of NAC voltages and notification modes; I will be able to switch between internal code wheel, external/pull station code wheel, and continuous output, and I will have a selection of NAC voltages to drive 6V to 120V appliances. The panel will even have a supervisory circuit!I drew up the PSU and main logic schematics in the span of an hour or so while I was at MEPS for an appointment, and a couple days ago I refined the PSU and made a much more official rev. B of it. I showed the PSU to a couple friends of mine who also work in the field of electronics but in more electrical engineering related fields than me, and one of them even specializing in power supply solutions. Both of them liked my circuit quite a bit, and I am curious to see what you guys would think. This is my first time actually designing one of these PSUs without a voltage regulator that does all the work for me, I had to make my own regulator for this one to stay true to the discreet circuits that would have been used back in the day. I'd definitely like to know if I messed something up here because I prefer to not fry my NAC lolThe main logic was the part that took me the longest. I rushed through it a bit but still wracked my brains trying to figure out a way to make it work. I still haven't refined this schematic yet, so it is very open to changes and in fact I would love ideas/suggestions before I ink a more official schematic for rev. B.The supervisory circuit I have not even gotten around to yet. I want to wait until I have a more official, refined main logic circuit so I can center my supervisory around it. My idea is that, like the older panels, I would have two large linear rheostats that would adjust the current to relays through the NAC and initiating devices (via EOL resistor) respectively. Enough current would flow to keep the relays on, but not enough would flow to initiate the notification appliances. This in theory would work for the NAC, but it kinda falls apart with the IDC because that one by default has 24V potential which would interfere with supervisory operation. I would absolutely love some ideas and suggestions on this! It is definitely a fun and interesting logic puzzle, that's for sure.The two main relays I have already picked out (K1 & K2 of the main logic schematic) and thus are not able to be changed. As a challenge to myself, I bought those two vintage relays so I could try to design a circuit around them. The other relays however are all fair game.This is quite a fun and interesting project that I am very invested in because the problem solving has been a nice change of pace from the monotonous "I've seen this problem a million times already and I know how to fix it" of general electrical equipment maintenance. I look forward to hearing your suggestions, answering your questions, and generally chatting about this fun little puzzle!