Emergency alert system for DHH public school students  - Page 1
Forum section: electronics / projects

author: Crector
author_rank: Newbie
timestamp: June 01, 2019, 12:05:53 am
content: Hi I’m new here but let me introduce the problem first. In the USA our Deaf and Hard of Hearing(DHH) students rely on teachers and interpreters to hear alarms over the intercom and communicate that to the DHH with American Sign Language. I became aware of this issue from a DHH instructor and am repeating her assessments of the problem. The obvious flaw in the current plan is that students are not constantly in the presence of a teacher, interpreter, or anyone else who might be able to communicate with those students. Laws are being updated that will require public schools to update their alert systems to include a visual alert as well but this “update” is only to retrofit strobe lights onto existing fire alarms. While that’s a step in the right direction it does not fundamentally communicate to the student the nature of the emergency so that student must still seek out a teacher or terp to find out what to do next. As you can imagine in a fire or active shooter situation that’s not ideal.My first thought was to solve this with a killer app but this introduces a new set of problems. In most American schools phones are prohibited and in many rural areas cell coverage can be spotty or not depending on cell carrier. Likewise WiFi might not be able to cover an entire campus, so cellphones aren’t a great option. What I needed is something that won’t be perceived as a classroom distraction that can receive signals over a wide area from a single broadcast location. Pagers seem to fit the bill. They can operate over a wide area from a single broadcast location with little interference from walls etc. My idea is to create a modified pager that vibrates and flashes an LED symbol to alert the student of the exact emergency. Text is actually less helpful for the majority of these students (ASL is their primary language and English is only a secondary for most of these students)I’d like to see something like this developed but I have no experience w radio electronics, no experience w programing radio broadcasts, and no experience w designing robust housings. 🤷‍♂️Anyway I’m C.H.A.D. I’m new here and I’d appreciate feedback.

author: sleemanj
author_rank: Super Contributor
timestamp: June 01, 2019, 12:19:42 am
content: Quote from: Crector on June 01, 2019, 12:05:53 amMake the strobe RGB, colour indicates required action.The required actions are evacuate immediately, lock down, proceed to assembly point, probably that's about it for an alarm situation so three easily distinguised colours, even for colour-blind that should be possible to get enough difference in intensity but can add in a flash/constant aspect as well.No need for kids to have thing on them which they will lose/break/forget.

author: Truglodite
author_rank: Newbie
timestamp: June 01, 2019, 08:34:39 pm
content: I agree with sleemanj, in that using distributed strobes may be less prone to failures. There's just too much that could fail with having students keep 'beepers' on hand (dead batteries, dropped while playing basketball, left it in the bathroom, etc...). Since we can't assume an ability to distinguish colors/contrast well, perhaps a system of coded flashes would work better. This could be done with repetitive simple patterns, like 1x flash for fire, 2x flashes for earthquakes, 3x for lockdowns, etc. I imagine, if such systems become required by law, that is how they might be implemented (where single purpose "fire alarm" switches around campus are replaced with multi function switches next to them for other situations).As far as implementation, ideally this could be integrated with existing fire strobe systems (which yes are a new requirement). The problem I see with that is you might be subject to the same red tape as fire system manufacturers (very drawn out/expensive process). So until laws are implemented that would grease those rails, you're probably best off making a standalone system.There are many ways you could implement this. For a typical school I imagine using a wireless mesh system would be best... that way an alarm can be triggered from several locations, and the integrity of the system wouldn't depend on one device that could fail/be disabled. This could be done using something as simple as an embedded system like ESP8266 modules inside waterproof boxes with batteries. For more spread out/noisy environments, you could use 433MHz radios in a non-wifi embedded system (like a pro-mini or similar). If you wanted to only allow staff to trigger special alarms, you could make pocket sized triggering radios for that (this would make the strobe units much simpler to build waterproof).All devices in the system should be designed so they self test periodically. One issue I imagine would come up is battery life/maintenance. Depending on how well it is designed, battery size, and how often the strobes are tested (presumably with monthly fire drills), this could become a significant expense. Adding solar could be a way to overcome this. Also it would be best to have a central monitoring node (like in the school office) that talks to all of the modules so it can alert staff of connection problems and low batteries.

author: Marco
author_rank: Super Contributor
timestamp: June 01, 2019, 09:01:10 pm
content: Maybe you could put clip on transformers on the wires for the existing alarms to transmit data? A high frequency carrier shouldn't do anything to the function of the standard siren/strobe receiving a T-3 alarm signal as a simple on/off signal. No need to cut the existing wiring, no need for extra wiring, no need for unreliable RF.Combine with the RGB light and just put a big sign next to it to indicate what colour means what.