Dilshan R Jayakody’s Web Log

This 12V uninterruptible power supply initially designs to drive my fiber optic modem/router. The key reason to build this power supply is to get continuous internet and phone connection during power failures. Core components of this power supply are a constant voltage charger, 12V DC power supply, AC line monitoring unit, and 12V high capacity sealed lead-acid battery. The entire system designs using locally available components. Prototype version of 12V UPS system The charging circuit of this system builds around using the popular LM350 voltage regulator. This regulator calibrates to provide both 14.4V fast charging and 13.6V trickle charging. Based on the condition of the battery, the MCU will determine the appropriate charging mode. At the online state, the LM2576-12 switching regulator provides 12V output to the driving system. (in my arrangement, a fiber optic router). Block diagram of the 12V UPS system The PIC16F688 MCU monitors the AC line and battery to controls the output...

This is modified version of commonly available automatic car battery charger system. I obtain original layout of this charger from one of the commercially available Chinese car battery charger and modified some of the sections of original schematic to improve the performance and stability of the system. This charger is mainly based on LM311 comparator and 2 ×12V 4A transformer. Final view of automatic car battery charger All the components of this car battery charger are commonly available in the market. Ammeter in this system must be withstand for minimum of 8A current. Low cost ammeter can also be used with suitable shunt. For the relay it is highly advisable to use some high quality unit. During our prototyping we mainly use 12V Omron and Panasonic realys with this system. At the test stages we observe that some of the cheap relays may start to oscillate heavily with this system. Automatic car battery charger finished prototype Under normal conditions TIP142 and 7805...