CCTV

At 1999, we were assigned to build CCTV together with fire alarm system, as requested by our customer. We invited many vendor to bid this project and again we were surprised their quotation was much higher than our budget. We, then, decided to make it ourselves and, thank God, we can make it.

We have to monitor 25 locations. 16 locations have to be recorded. The other 9 locations are used just for monitoring purpose. Unlike common CCTV that monitoring is centralized in security guard’s room, in our system, monitoring all 25 locations can be done anywhere.

The concept is also simple. Signal from CCTV 1 is modulated (converted) into TV signal at frequency 1. CCTV 2 is also modulated into TV signal at frequency 2 until all 25 units CCTV. Theoretically, we can monitor up to 32 units CCTV on two groups, each 16 units. Among TV signal must not interfered each other, like commercial TV. Signal from each group are summarize by using RF combiner. Signal from RF Combiner 1 is fed into RF Combiner 2. Now on, output from RF Combiner 2, will consist of 32 TV frequencies. This frequency is amplified by using wide band RF Amplifier before distributing to TV. To see each CCTV is very simple, just to select TV signal, i.e. CCTV 1 on channel 1, CCTV 2 on channel 2, etc.

Fire Alarm System

Few years ago, we have been assigned to build integrated fire alarm system and CCTV. We have 3 manufacturing buildings and 1 office. Fire alarm of these 4 buildings must be integrated and monitored from security room. The system consists of many smoke detectors. To integrate each smoke detector, we use cable. The longest distance between fire detectors and control room is more than 1 km. We invited many companies to bid. We were surprised their quotations were very expensive. We, then, thought why didn’t we build the system ourselves? We already had the concept and we were sure that we could make it.

The concept is simple. Master (Smoke Detector Central Monitor) ask data start from slave 1, slave 2 until slave n.. Slave’s data is smoke detector condition: in danger (smoke) or not. All smoke detectors data, on central monitor, will be displayed. Monitor can be a simple monitor (just small lamp and 3 digits number), computer system or even through internet. Monitoring period of each slave is very fast (only few seconds) so its look like all smoke detectors condition’s be displayed instantaneously. If there is a fire, the nearest alarm (of the fire) and central monitor’s alarm will be ring. Security guard will immediately know fire and its location.

The advantage of this system is we only need one wire (backbone) to connect master and all slaves. The maximum backbone length is 1.5 km, and we already make it. Theoretically, we can have 225 units slave and 20 units alarm. Each slave monitor 4 sets smoke detector or total 900 units smoke detector in the system. We can use smoke detector that have data connection (preferred) or just simple or stand alone smoke detector. From above picture, based on arrow direction, master and slave communication are two ways while alarm and smoke detector are only one way communication.

We use RS-485 technology to ensure 1.5 km backbone length communication work well. If you are interested in master-slave system in electronics view, please visit….. RS-485 technology also can be studied further in ….