Author Topic: Safety precautions for homemade USB Lamps Advice Needed  (Read 173 times)

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Offline electroDart

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Safety precautions for homemade USB Lamps Advice Needed
« on: September 15, 2019, 09:18:39 pm »
I make USB lamps as a hobby, but I would like to sell them at some point.
They are basic parallel series of leds, each LED has its own resistor to bring it to around 20ma max current.
I use the chinese dc-dc 0.9-5v boost boards for the battery powered ones.
I use an epoxy potted micro usb socket, just the vbus and gnd soldered ( no negotiation ) for the usb powered ones.

I want to make the usb lamps as safe as I possibly can, to account for user error. I'm concerned about two things. 1. that someone will connect the lamp to very expensive laptop usb port and it could cause damage. 2. that someone will connect it to a knockoff usb charger which could overvolt it and cause a fire.

I already have a set of 500ma self healing fuses ( 1206 from china ), and some other THT ones at 400ma from the UK.

Any advice on how to proceed would be greatly appreciated. I did wonder if just connecting the usb 0.9-5v dc-dc board might do the trick as they already seem to contain fuses.

Thanks.
 

Offline james_s

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Re: Safety precautions for homemade USB Lamps Advice Needed
« Reply #1 on: September 15, 2019, 11:15:52 pm »
USB ports are already quite safe, they are low voltage and current limited. There is nothing you need to do other than make sure you don't have sharp edges or toxic substances, if you want to add a low current fuse that won't hurt anything but it shouldn't really be necessary.
 

Offline Fredled

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Re: Safety precautions for homemade USB Lamps Advice Needed
« Reply #2 on: September 20, 2019, 09:08:04 pm »
I would recommend to power your leds at less than 20mA. That way they will be less likely to fail and take too much current.
A self ressetable (self healing) fuse is a good, inexpensive solution. But it's necessary only in case of damage to the led light causing a short cicruit. Normal use should never be dangerous for any device.
 

Offline james_s

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Re: Safety precautions for homemade USB Lamps Advice Needed
« Reply #3 on: September 20, 2019, 11:35:14 pm »
You can probably go even cheaper with an ordinary fuse or fusible resistor. If part of the device fails, chances are it will go into the trash. Self resetting fuses are only really useful for devices that connect to external devices that could present a recoverable fault condition.
 


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