Posted on Thursday, October 21, 2010 • Category: Battery Chargers
Here is a lead acid battery charger circuit using IC LM317.The IC here provides the correct charging voltage for the battery. A battery must be charged with 1/10 its Ah value. This charging circuit is designed based on this fact.The charging current for the battery is controlled by Q1,R1,R4 and R5. Potentiometer R5 can be used to set the charging current. As the battery gets charged the the current through R1 increases.
Posted on Thursday, October 21, 2010 • Category: Power Supplies
For circuits using TTL ICs the supply voltage is a great concern and a slight increase in supply from the rated 5V may damage the IC. Using fuses alone does not solve the problem because a fuse may take several milliseconds to blow off and that’s enough time for the IC to get damaged.
Posted on Thursday, October 21, 2010 • Category: Miscellaneous
Here is the circuit diagram of an ultrasonic mosquito repeller.The circuit is based on the theory that insects like mosquito can be repelled by using sound frequencies in the ultrasonic (above 20KHz) range.
Posted on Tuesday, October 19, 2010 • Category: Battery Chargers
This is a portable USB Charger. It uses a high efficiency switching regulator that runs at 85 - 94% efficiency depending on input voltage and load.
It takes an input voltage from 8 to 16 volts and can run from anything from a 9 volt battery to a car battery.
It has 2 USB ports and easily charges 2 power hungry devices at once.
Posted on Tuesday, October 19, 2010 • Category: Video
Here's a simple video transmitter for VHF TV channel will accept baseband video input, hence it can be driven by most CCD cameras and VCR video outputs. It ouputs roughly 80mW and when used with a 40cm telescopic antenna over 100 meters range is possible.
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