Nepalien
New Member
Hello all,
I have a short wave receiver that requires 4.5V power. Usually I use AC adapter but during power outage (which is frequent in Kathmandu), I use 3 D sized batteries. Current drain by the radio is around 120 mA for comfortable listening (AM mode with Sync detector ON). Listening to FM consumes around 100 mA. However it does vary but the maximum is not more than 150 mA.
I am thinking of using 12V and 7805 regulator to power this puppy. But I want to design the power supply that accomplish following things:
1. Voltage output should be 4.5V
2. Current should be limited to 150 mA
3. Any other protection that is required (for instance what if input polarity is reversed by mistake)
I have thought of putting a 5Ω 5W resistor to drop 0.5V at 100 mA in 7805 output. And for current protection, I want to put 200 mA fuse also. Finally I want to house this simple circuit in good old film roll plastic box with few holes for ventilation.
I would appreciate any inputs for this project. I really don't want to make one simple mistake and destroy the radio. Thanks for reading and Namaste from Nepal!
I have a short wave receiver that requires 4.5V power. Usually I use AC adapter but during power outage (which is frequent in Kathmandu), I use 3 D sized batteries. Current drain by the radio is around 120 mA for comfortable listening (AM mode with Sync detector ON). Listening to FM consumes around 100 mA. However it does vary but the maximum is not more than 150 mA.
I am thinking of using 12V and 7805 regulator to power this puppy. But I want to design the power supply that accomplish following things:
1. Voltage output should be 4.5V
2. Current should be limited to 150 mA
3. Any other protection that is required (for instance what if input polarity is reversed by mistake)
I have thought of putting a 5Ω 5W resistor to drop 0.5V at 100 mA in 7805 output. And for current protection, I want to put 200 mA fuse also. Finally I want to house this simple circuit in good old film roll plastic box with few holes for ventilation.
I would appreciate any inputs for this project. I really don't want to make one simple mistake and destroy the radio. Thanks for reading and Namaste from Nepal!
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