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Fuse Rating for Automotive Application
I have a regulated DC Adapter with the following specs:
input: 12V DC (from cigarette lighter socket) output select: (3, 4.5, 6, 7.5, 9, 12)V DC, 0-300mA Is a "1A, 125V" fuse safe enough to use (for the sake of protecting the car battery and the electronics connected to the adapter)? What is a "typical" fuse in such an environment for use with portable electronic gadgets? Any hard data for typical ranges for current and voltage spikes during car ignition? Thanks Al-U |
#2
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alpha_uma wrote:
I have a regulated DC Adapter with the following specs: input: 12V DC (from cigarette lighter socket) output select: (3, 4.5, 6, 7.5, 9, 12)V DC, 0-300mA Is a "1A, 125V" fuse safe enough to use (for the sake of protecting the car battery and the electronics connected to the adapter)? What is a "typical" fuse in such an environment for use with portable electronic gadgets? Any hard data for typical ranges for current and voltage spikes during car ignition? Thanks Al-U Hi, A 1 amp fuse is probably the smallest you are going to be able to find for automotive usage. As far as protecting the battery etc. remember that the cigarette lighter circuit already has a fuse in case something goes horribly wrong. I wouldn't think that there is a "typical" fuse for anything, it depends on what your load is going to be, that is where the "typical" comes in. Your total load for the adapter is never going to be above 300mA which is less than one amp, your adapter probably has some kind of thermal overload built into it that will shut it down if the load goes over 300mA. Check under the dash for your cigarette lighter's circuit's fuse, it is probably 15 amps, as long as you do not plug anything into the cigarette lighter socket that exceeds your fuse rating you should be fine. -Landon |
#3
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"Landon" wrote in message
... alpha_uma wrote: I have a regulated DC Adapter with the following specs: input: 12V DC (from cigarette lighter socket) output select: (3, 4.5, 6, 7.5, 9, 12)V DC, 0-300mA Is a "1A, 125V" fuse safe enough to use (for the sake of protecting the car battery and the electronics connected to the adapter)? What is a "typical" fuse in such an environment for use with portable electronic gadgets? Any hard data for typical ranges for current and voltage spikes during car ignition? Thanks Al-U Hi, A 1 amp fuse is probably the smallest you are going to be able to find for automotive usage. As far as protecting the battery etc. remember that the cigarette lighter circuit already has a fuse in case something goes horribly wrong. I wouldn't think that there is a "typical" fuse for anything, it depends on what your load is going to be, that is where the "typical" comes in. Your total load for the adapter is never going to be above 300mA which is less than one amp, your adapter probably has some kind of thermal overload built into it that will shut it down if the load goes over 300mA. Check under the dash for your cigarette lighter's circuit's fuse, it is probably 15 amps, as long as you do not plug anything into the cigarette lighter socket that exceeds your fuse rating you should be fine. -Landon Thanks for replying. Yes, the car's cigarette lighter circuit already has a 15A fuse under the dash. The "1A" fuse (specified by the DC adapter's manufacturer caution against fire hazard) is actually inside the DC adapter. It has burnt out. ... your adapter probably has some kind of thermal overload built into it that will shut it down if the load goes over 300mA. I hope so. Is there any relationship--direct or indirect--between the 1A rating of the fuse and the 300mA output rating of the adapter? Or is that something only the manufacturer's engineers would know? Would a max rating of 300mA be enough to power a laptop computer? Al-U |
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alpha_uma wrote:
"Landon" wrote in message ... alpha_uma wrote: I have a regulated DC Adapter with the following specs: input: 12V DC (from cigarette lighter socket) output select: (3, 4.5, 6, 7.5, 9, 12)V DC, 0-300mA Is a "1A, 125V" fuse safe enough to use (for the sake of protecting the car battery and the electronics connected to the adapter)? What is a "typical" fuse in such an environment for use with portable electronic gadgets? Any hard data for typical ranges for current and voltage spikes during car ignition? Thanks Al-U Hi, A 1 amp fuse is probably the smallest you are going to be able to find for automotive usage. As far as protecting the battery etc. remember that the cigarette lighter circuit already has a fuse in case something goes horribly wrong. I wouldn't think that there is a "typical" fuse for anything, it depends on what your load is going to be, that is where the "typical" comes in. Your total load for the adapter is never going to be above 300mA which is less than one amp, your adapter probably has some kind of thermal overload built into it that will shut it down if the load goes over 300mA. Check under the dash for your cigarette lighter's circuit's fuse, it is probably 15 amps, as long as you do not plug anything into the cigarette lighter socket that exceeds your fuse rating you should be fine. -Landon Thanks for replying. Yes, the car's cigarette lighter circuit already has a 15A fuse under the dash. The "1A" fuse (specified by the DC adapter's manufacturer caution against fire hazard) is actually inside the DC adapter. It has burnt out. ... your adapter probably has some kind of thermal overload built into it that will shut it down if the load goes over 300mA. I hope so. Is there any relationship--direct or indirect--between the 1A rating of the fuse and the 300mA output rating of the adapter? Or is that something only the manufacturer's engineers would know? Would a max rating of 300mA be enough to power a laptop computer? Al-U Your adapter has a 1 amp fuse because that is the smallest that you can find for automotive uses, there are probably some that are smaller but they are hard to find. 1 amp also equals 1000mA. I seriously doubt that 300mA is going to power your laptop, my little portable CD player runs on something near 400mA and all it is is a little motor, a laser, and a small audio amplifer to power the headphones. Check the sticker on the laptop for its power requirements, it probably says 120 volts; 50/60 Hz.; and then the amperage is probably something between 3 and 6 amps (3000mA and 6000mA), or it may not have the amperage and just list the wattage. Your best bets for running it from the cigarette lighter jack are getting an adpater that was specifically made for your laptop to run from the cigarette lighter jack, or getting a power inverter that converts the 12 volts DC to 120 volts AC then just plugging the laptop into that. Good luck. -Landon |
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