In principle - Yes, and there are "Y cables" sold/provided with USB hard/CD/DVD drives that do this. However, my experience and measurements suggest that this is really "only" possible with ports on netbooks/laptops/motherboards, and that many (cheaper) "powered" USB hubs are either built with their ports "already in parallel w.r.t. power" and/or supplied with inadequate power supplies. Your D-Link product, being "not so cheap" may be an exception of course. FWIW I've posted my measurements & test methods etc. within my webpages - start at http://www.cpmspectrepi.webspace.virgin ... index.html and then "rummage around at your leisure"Antivirusvivente wrote: I'm 18 and i'm studying electronics at school, but i don't know too much, is it possible to connect two of these USB wiring the positive with the positive of the other one USB, and the negative as before, if i'm right, i should get 500mA+500mA=1A, right?
This is my 8channel relay ( http://www.dib-bid.com/gallery/8-channe ... ule_02.jpg ), do you have this one?pjc123 wrote:Take a look at the Lambda LS series of power supplies for your 5V 2A+ application. Their smallest model (LS25-5) has a 5V - 5A capacity, is small (3.1L" x 2.0W" x 1.1H"), inexpensive and very high quality. There are other manufacturers of this type of switching supply as well. I am using an LS50-12, 12V - 4.2A supply that I drop down to 5V because I have several 5V and 12V devices associated with my pi. I also have an 8 channel relay board, and on mine there is a jumper that allows you to run the high current part of the board (coil) off of an external supply, while running the trigger portion of the relay board (opto LED) off of the pi's GPIO 5V line, which is how I do it.
The problem is that a lot of people activates the relays directly the GPIO, instead I use a microcontroller, the bv4111, which is explained here: http://doc.byvac.com/index.php5?title=Product_BV4111pjc123 wrote:I have a visually identical board (but a warning: no guarantee it is exactly the same because there are some minor differences on these boards), but here is how the Sainsmart board works:
Schematic for the Sainsmart:
http://www.sainsmart.com/8-channel-dc-5 ... logic.html
If you don't know how to hook up the rest, it has been discussed in this forum ad nauseam with almost a years worth of schematics, pretty pictures, paint by numbers, idiots guides to 8-channel relays, heated debates, etc. Hint: Google search.
Hard to say for sure unless you have the specs of the devices on the relay board, but being a 5V board, I suspect there is at least that much leeway with the opto, transistor and diode. The coil and resistor would be OK. Just don't use that power supply to power the pi, because acceptable range for the pi is between 4.75 and 5.25 .Antivirusvivente wrote:Ok I connected JDVcc and GND with an external 5V 1.5A power supply and the relays work very well.
Now i was wondering.. the output 5v is around 5.3 and 5.5v, even it's declared 5v. Could it make any trouble?