PDA

View Full Version : powering grinch with usb?? is it possible



fathead45
06-11-2009, 05:42 PM
im just wondering if you can power the grinch with pin 1 (+5vdc) and pin 4(ground) to J2?? the usb is enough to power the grinch. maybe its been answered before but i just havent found it. i hope it would work as i have all the stuff to make it work.

thanks

dirknerkle
06-11-2009, 05:54 PM
Yes, you can grab power from USB, and if you need more, you can use two USB ports. Of course, you need the powered ports....

Watch it though -- if you draw too much current you can fry your computer's motherboard. I think you can realistically get only about 500ma out of a port, but it also depends on the computer's design -- some may not allow even that much. A laptop, for instance, is usually pretty low while a desktop can deliver more oomph.

What is safer is to use an external powered USB hub. They typically provide a much heftier jolt of electricity, and it's a lot less expensive to replace an external hub than a motherboard....

-dirknerkle

P. Short
06-11-2009, 10:06 PM
Each SSR will draw about 35 mA (10 mA for the power LED and 6 mA for each ON channel), so a fully loaded Grinch with all 64 channels ON would draw over 1A. This would be over twice as much as a full-powered USB port will supply. In addition, many (if not all) USB ports will only supply 100 mA until some USB peripheral negotiates for more power...so I would only use a USB port to power a Grinch for testing purposes, not for regular use.

scorpia
06-11-2009, 11:43 PM
long answer. see above.

short answer.... dont,

fathead45
06-12-2009, 07:09 AM
alright, thanks guys. i mostly wanted it for testing. im going to make a plug that goes in a power plug off the power supply.

thanks alot.

mrpackethead
06-12-2009, 05:30 PM
alright, thanks guys. i mostly wanted it for testing. im going to make a plug that goes in a power plug off the power supply.

thanks alot.

if its a PC powersupply, i'd highly suggest you fuse it.. A PC power supply has enough grunt to deliver plenty of current, that will melt things if you do somethign silly! Maybe a 2A fastblow fuse will cover you.

daviddth
06-14-2009, 03:13 AM
I totally agree, a PC power supply certainly can deliver a lot of current. The modern ATX ones will usually shut down on a short circuit, but that might not be fast enough to save small tracks on boards.

I use 2A fast blow fuses to each item, and a 10A slow blow on the main outcomer from the power supply's 5V rail.