I would really like to make an automatic power failure emergency light, I have discovered modules which can take a 5V source to charge an NIMH 3.6 or 3.7v li-ion battery, modules available for either battery types. I have drawn a diagram below which shows an NIMH 3.6V pack using a NIMH charging module that charges at 4.5V DC. The module can both accept a 5V USB or power adaptor source, I also have a module which is a switched mode 5V DC 700mah source which can take in 120/240v AC.
In my design however my choice will be a normal 5V power adaptor which will plug into an AC socket. In my diagram you can see a main power source of DC 5V which is connected to an NIMH charging module which will properly charge a 3.6V NIMH battery pack.
Connected in parallel on the DC 5V input source is a set of wires which connect to an auto switching board and vice versa on the battery terminal wires. The output from the switching module will be a white LED maybe several. I'm aware a relay is a common component along with a rectifier, resistor or 2 and a some diode.
When the 5V power is active, the LED is obviously off and the battery is charging, When the power fails, the charging will stop and the switching unit will detect that and switch over to the battery illuminating the LED's until main power is restored and battery recharges.
Please can someone give me the circuit diagram and component list required with the input for the battery, main 5V source and output for LED's. A complete circuit would be also appreciated with all functions on a single PCB for charging and switching. I just want to ensure the battery is correctly charged and won't be overcharged, overheated or damaged.
I've found plenty circuits for building 12V automatic emergency lights and have successfully built one years back, using a 12V 1.2ah lead acid battery which lit a couple of 12v MES bulbs for 3-4 hours.
A note for those who want an easy to find regulated DC 5V 700mah power source which can take in 120/240v AC - Samsung mobile phone charges used with phones from the early to mid 2000's with p/n: TAD037UBE. Just open the plug with a torx screwdriver and there you go a lovely module! ;-)
In my design however my choice will be a normal 5V power adaptor which will plug into an AC socket. In my diagram you can see a main power source of DC 5V which is connected to an NIMH charging module which will properly charge a 3.6V NIMH battery pack.
Connected in parallel on the DC 5V input source is a set of wires which connect to an auto switching board and vice versa on the battery terminal wires. The output from the switching module will be a white LED maybe several. I'm aware a relay is a common component along with a rectifier, resistor or 2 and a some diode.
When the 5V power is active, the LED is obviously off and the battery is charging, When the power fails, the charging will stop and the switching unit will detect that and switch over to the battery illuminating the LED's until main power is restored and battery recharges.
Please can someone give me the circuit diagram and component list required with the input for the battery, main 5V source and output for LED's. A complete circuit would be also appreciated with all functions on a single PCB for charging and switching. I just want to ensure the battery is correctly charged and won't be overcharged, overheated or damaged.
I've found plenty circuits for building 12V automatic emergency lights and have successfully built one years back, using a 12V 1.2ah lead acid battery which lit a couple of 12v MES bulbs for 3-4 hours.
A note for those who want an easy to find regulated DC 5V 700mah power source which can take in 120/240v AC - Samsung mobile phone charges used with phones from the early to mid 2000's with p/n: TAD037UBE. Just open the plug with a torx screwdriver and there you go a lovely module! ;-)
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