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Discussion Starter · #1 ·
I have a question for the Electrical Guru's out there. I would like to reduce 12 volts down to 5 volts 1 amp. What do I neeed in the way of capaciters, diods, and disgruntificators to do this?

Thanks for the help.

Rich
 

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Gregarious Greeter
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A ballast resistor should do the trick.:waving:
 

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Just one of the guys
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A ballast resistor should do the trick.:waving:
A resistor will reduce the voltage but only to a known load and a calculated resistance. If the load varies so does the voltage. Example a ballast resistor in a ignition circuit reduces the voltage at idle but as RPM increases so does the voltage to the coil.
 

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Use an LM7805 voltage regulator chip. They sell for a couple dollars and can be bought at any electronic supply house, including Radio Shack. You will need a heat sink with it and a couple small external components. Easy to wire up. Just Google LM7805. This will give you 5 volts at 1 amp maximum current. It will maintain 5 volts regardless of the load.
 

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Use an LM7805 voltage regulator chip. They sell for a couple dollars and can be bought at any electronic supply house, including Radio Shack. You will need a heat sink with it and a couple small external components. Easy to wire up. Just Google LM7805. This will give you 5 volts at 1 amp maximum current. It will maintain 5 volts regardless of the load.
I agree, use a 7805 regulator, the stability of the voltage will be much better and trying a dropping resistor. A LM7805 will regulate voltage from 7-25 volts and still produce [email protected] With a dropping resistor you voltage will vary with the voltage supplied.
 

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Discussion Starter · #9 ·
Thank You everone. I am working on a USB hub for my GL1500. I've seen the single USP chargers, they would work if I only had 1 item to charge. I am trying to make a multi-port hub work. The problem is that it needs an external power supply to use as a power hub. The reason I want a Multi-port charging solution is that my wife and I use the Scala G4 Powerset, then add in a couple cell phones, and sometimes a camera.

I will probably go the LM7805 route. Now to search out the wiring diagram.

Will the LM7805 produce much heat?

Thanks everyone.
Rich
 

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Still a winger at heart.
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a solid state regulatoris the key. Watch the amp rating... You can toss caps on there to smooth it out, but it may not be necessary



 

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Thank You everone. I am working on a USB hub for my GL1500. I've seen the single USP chargers, they would work if I only had 1 item to charge. I am trying to make a multi-port hub work. The problem is that it needs an external power supply to use as a power hub. The reason I want a Multi-port charging solution is that my wife and I use the Scala G4 Powerset, then add in a couple cell phones, and sometimes a camera.

I will probably go the LM7805 route. Now to search out the wiring diagram.

Will the LM7805 produce much heat?

Thanks everyone.
Rich
They do produce a little heat, not to bad, use a TO220 heat sink if your going to use the TO220 configuration. It is the one in the diagram posted.
 

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Still a winger at heart.
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If the mounting tab on the regulator is mounted to an aluminum plate, it could be enough. When I did this same project as a dash regulator in the 70 mustang, I used an old pc processor heat sink.
 

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Monkey with a Football
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Heat is a function of how much current you are regulating and what the dropping voltage is and is rated in watts. If you regulate at 5 volts and your operating voltage is, say 13v, then you are dropping 8 volts at 1 amp or 8 watts. The regulator you use will have a maximum wattage rating and assumes this with an infinite heat sink.
Of course if you only draw 500 ma then your wattage would also drop to 4 watts.
The typical TO-220 package of the LM7805T is rated around a maximum wattage of 15 watts so you would be ok with a smaller heat sink but I would not recommend using it without one.

Also if you plan to use multiple outlets, I would use a separate regulator for each one unless you know their total loads would stay fairly low.
 

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Discussion Starter · #14 ·
It sounds like I have a trip to Radio Shak coming up. If this works, I'll post the info and some pix.

Thanks,
Rich
 

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Just one of the guys
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Would a standard desktop type of USB hub provide charging current? I have never used one but I suspect it would. That might make for an easy to install solution.

[ame]http://www.amazon.com/Black-4-Port-High-Speed-USB/dp/B002FFT8Z6/ref=sr_1_8?s=electronics&ie=UTF8&qid=1353022247&sr=1-8&keywords=USB+hubs[/ame]
 

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I will probably go the LM7805 route. Now to search out the wiring diagram.

Will the LM7805 produce much heat?

Thanks everyone.
Rich[/QUOTE]

Yes. You will need to install it on a small heatsink, and use thermal paste.
 

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Heat is a function of how much current you are regulating and what the dropping voltage is and is rated in watts. If you regulate at 5 volts and your operating voltage is, say 13v, then you are dropping 8 volts at 1 amp or 8 watts. The regulator you use will have a maximum wattage rating and assumes this with an infinite heat sink.
Of course if you only draw 500 ma then your wattage would also drop to 4 watts.
The typical TO-220 package of the LM7805T is rated around a maximum wattage of 15 watts so you would be ok with a smaller heat sink but I would not recommend using it without one.

Also if you plan to use multiple outlets, I would use a separate regulator for each one unless you know their total loads would stay fairly low.
Rick is always there with helpful advice... :claps: :claps: :claps: :gunner:
 

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Discussion Starter · #18 ·
Would a standard desktop type of USB hub provide charging current? I have never used one but I suspect it would. That might make for an easy to install solution.

http://www.amazon.com/Black-4-Port-...=UTF8&qid=1353022247&sr=1-8&keywords=USB+hubs
I'm hoping to use a desktop hub. That is what I'm atleast hoping to do. I've tossed so many out in the past, now I'm kicking myself. I need to pick one up that has the AC charger, then see what the output is on the charger. If it's 12 volts, then the hub will reduce the voltage for me. I will only have to add a fuse. If the voltage is 5 volts, then I will need to use the regulator. I'm a cheapskate, and I know I can but USB power outlets for $25 each, but I can buy a powered hub for as low as $15, and get multiple ports.
 

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Geez, I wish some of you electrical gurus lived near me - I can't even figure out the wiring of all the accessories by the previous owner, let alone the theory you are dealing with. I'm good at some things (none that save money) but not this and REALLY admire the knowledge you folks have. About the only way I could reduce voltage/amps is leave the stinkin' key on overnight...
 

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I'm hoping to use a desktop hub. That is what I'm atleast hoping to do. I've tossed so many out in the past, now I'm kicking myself. I need to pick one up that has the AC charger, then see what the output is on the charger. If it's 12 volts, then the hub will reduce the voltage for me. I will only have to add a fuse. If the voltage is 5 volts, then I will need to use the regulator. I'm a cheapskate, and I know I can but USB power outlets for $25 each, but I can buy a powered hub for as low as $15, and get multiple ports.
Be a bit careful when applying "Battery or Alternator" voltage to a 12V device. Your battery will typically be around 12.5V when the system is not charging and when the Alternator kicks in the voltage can get up to and slightly over 15V's.

The hub you mention may not like having its input voltage 25% over its normal input of 12V. Be prepared to waste a hub or two while experimenting.

If it is a hub powered by 5V in then each port typically can source no more than 1/2 amp and most may only source 1/4 amp. That is fine for charging most phones or mp3 players but it is not enough for charging an iPad. Trying to pull to much through the ports on a USB Hub will send them into auto-shutdown and you will have to cycle the power on them to get them back on.

The drawing Dick (UBarW) provided is right out of the manufacturers specifications and will work well. Like everyone else stated make sure you use a heatsink or you will end up replacing the regulator after you let out the smoke.

I just picked up a 100Watt inverter at Home Depot that plugs right into the outlet and it includes a USB plug on it. Total cost was 9.95 before taxes. This may be a cheaper and faster way for you to go.
 

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