how to convert a 12v 6.5amp dc to a 12v 1.5amp dc  - Page 1
Forum section: electronics / beginners

author: newboy857
author_rank: Newbie
timestamp: August 10, 2020, 10:23:30 pm
content: Hi I have a power brick I need to convert for a projectas I said its running at 12v 6.5amp and I need to step the amp / current down to 1.5amp dcI keep seeing LM317 mentionedis there a buck convertor equivalent that will assist on amp'salso why is it the buck convertors i've seen state output amps and not input ampsmany thanksDarren

author: ledtester
author_rank: Super Contributor
timestamp: August 10, 2020, 10:40:28 pm
content: You don't need to do anything.Describe why you think you need to modify the power supply and we'll explain why it's not necessary.

author: newboy857
author_rank: Newbie
timestamp: August 10, 2020, 10:56:09 pm
content: thanks the device i need to connector my power brick to will only accept up to 3 amp supplies, which is why I believe I need to reduce the amps before connectionSo i believe I have to introduce something between then two to reduce the amp's and keep the voltsI cant afford to fry my piece of kitthanks

author: greenpossum
author_rank: Frequent Contributor
timestamp: August 10, 2020, 11:04:02 pm
content: That just means the device will need up to 3A. If your power supply can supply more, it's not a problem, it just won't be called upon to supply that much. It's like saying you need to drive 100 km but your car tank has a range of 300 km.

author: ledtester
author_rank: Super Contributor
timestamp: August 10, 2020, 11:10:44 pm
content: Quote from: newboy857 on August 10, 2020, 10:56:09 pmI'm sure what it meant is that the device needs a power supply that can supply at least 3A of current not at most 3A of current.

author: Nusa
author_rank: Super Contributor
timestamp: August 10, 2020, 11:13:59 pm
content: Amp ratings are how much a power supply is capable of delivering. How much it WILL deliver is determined by the device(s) attached to it. If you need to convince yourself, find a 12V light bulb and attach it to your existing supply.But if you want to feel extra safe, you can always put a 2 amp fuse between the power supply and your 1.5 amp device. Just make sure you get the polarity right. Swapping + and - is one of the more common ways of breaking things.

author: newboy857
author_rank: Newbie
timestamp: August 11, 2020, 12:02:30 am
content: i really appreciate all your feedbackI've never thought of Amps in this way, always assumed it was the mysterious killer of devices, but the car tank approach proved light bulb moment, the brick has a limit of 6 amps but can supply anything below that on need.going to place a mosfet P (FQP47P06) on my circuit to stop the cable from being plugged in the wrong way, I was aware of diodes, but not on how much heat they can kick out the mosfet P is a nice approach, youtube clip for those interested.I might get a buck convertor so I can trim the volts down as I'm not sure if this power brick is regulated and they are really cheap to get hold of.the project I'm working on is to strip out an old pc in a touch screen hmi in manufacturing environment.install a lcd driver M.NT68676.2A which then enables hdmi /vga to a led panel, which I have and works great. Then I've connected the touch screen / converted with a simple cable to usb connector.now just want to use the old power bricks, make sure I stop any fool from reversing the power as its a choc block power type connector. and hey presto a touch screen awaiting a nice NUC computer.Instead of a dual core atom from 8 years ago.Thanks to allDarren

author: james_s
author_rank: Super Contributor
timestamp: August 11, 2020, 12:12:41 am
content: It's more like the weight capacity of a truck than the size of the fuel tank. You need to haul something that weighs 400 pounds but all you've got is a truck with a 2,000 pound capacity. No problem, you don't need to find 1600 lbs of bricks to make up the rest of the weight rating, doing so would just be wasting energy and effort and increasing wear & tear on the truck. Instead you just load in what you've got and as long as your load does not exceed the maximum the truck is rated to carry you will be fine.If you're not sure if the power source is regulated, measure it with your multimeter to find out. Don't add extra conversion stages unless you need to, each time you step the voltage down or up you will be throwing away around 10% of the total you start out with.