Antivirusvivente
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The Right Power Supply

Wed Apr 17, 2013 4:28 pm

Hi guys!
This time I need help to solve a future issue. I bought a USB Hub, a D-Link DUB-H7, which is fed by a 5v 3A and provides 0.5A for each USB port. ( here's a link: http://www.dlink.com/us/en/home-solutio ... sb-2-0-hub )

I used to power the Pi by the 1st one port, using Fast-Charge mode, but i also need this hub to fed other devices such as webcam and external hdds ( in this case, the 1st two ports go in normal mode, so 0.5mA ).

I connected a lot of devices, and i suppose it's not enough, i connected:
- RaspberryPi ( at least 700mA )
- bv4111 ( Relay Controller + 8Channel Relay ) almost 650mA
- bv4618 + HD47780 ( almost 3mA )
- 8 PIR sensors HC-SR501( datasheet says 50uA for each ) ( two for now )
- DS18B20 Thermal Sensor
- MCP23017 ( it's going to arrive )

I guess that only the 8Channel Relay requires a lot of mA, the rest uses a power that the GPIO can handle without problems.. i guess..

So, what can be the solution? May I supply some of these components from the hub itself?
Is it possible to prevent to buy another one supply for my Pi? Maybe using something that I already have. Thanks for the help
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maheanuu
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Re: The Right Power Supply

Wed Apr 17, 2013 5:05 pm

I believe that the Hub is your answer, you might consider powering the Relay Unit with a separate power supply, but for ide or sata drives I would recommend using a good hub with a minimum capacity of >3 amperes.

Being a newbie Raspbarian myself, I am still learning, but having been an Electronics Technician for over 50 years, I can tell you that the current draws in parallel do not affect the current draw by the RaspberryPi itself.

Having said that, I wish you well in your endeavors, and happy building and learning. I still am learning and building myself and am past the 3/4ths of a Century mark...

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Re: The Right Power Supply

Wed Apr 17, 2013 5:33 pm

Thank you for your encouragement, maheanuu.. but now a question arises..

Should I use a 1.2A power supply or two of my available USB ports to supply the relays and maybe PIRs?

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?

Just right this one: http://www.r-digital.it/images/Cavi_mul ... avo-MM.jpg
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maheanuu
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Re: The Right Power Supply

Wed Apr 17, 2013 5:54 pm

That would probably work, but do you want to use up 2 of your USB ports when you probably have, or can find a used 5 V plug in supply in the 2 to 3 amp range that would more than be adequate for your needs. I am not familiar with the Relay Unit, is it USB powered or does it just have a separate input jack to power it up? More info makes me a happy camper when it comes to this sort of problem....

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Re: The Right Power Supply

Wed Apr 17, 2013 6:05 pm

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?
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" :)
Trev.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, and a A+) but Buster on the P4B's. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

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Re: The Right Power Supply

Wed Apr 17, 2013 6:18 pm

In other words.. i need a 5v supply that provides me more than 2A. So in this case i will not have problems on my devices connected to the GPIO, isn't it?

I'll have:
5v 2A+ to supply Pi+Devices ( Relays, PIRs, LCD.. )
5v 3A 7Port Hub to supply Hard Disks, webcams and so on..

Can you please suggest me a good and tested supply to buy?

I have an external hard disk drive power supply that i don't you use anymore, it has 1.5A on the 5v rail.
It's like this: http://img3.buyincoins.com/show/hd-disk ... supply.jpg

Can i supply all the devices with this?
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pjc123
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Re: The Right Power Supply

Wed Apr 17, 2013 7:40 pm

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.

http://us.tdk-lambda.com/lp/products/ls-series.htm
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Re: The Right Power Supply

Wed Apr 17, 2013 8:39 pm

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.

http://us.tdk-lambda.com/lp/products/ls-series.htm
This is my 8channel relay ( http://www.dib-bid.com/gallery/8-channe ... ule_02.jpg ), do you have this one?
If you have, would you please tell me how to connect an external supply directly to this board?
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Re: The Right Power Supply

Thu Apr 18, 2013 2:16 am

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:

http://www.raspberrypi.org/phpBB3/viewtopic.php?t=19222

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.
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Re: The Right Power Supply

Thu Apr 18, 2013 12:08 pm

pjc123 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:

http://www.raspberrypi.org/phpBB3/viewtopic.php?t=19222

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.
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_BV4111

Now i connect the bv4111 to the tx,rx, 3.3 and GND connectors, and the 5v GPIO directly to the 8relay board vcc.

A question arises, if I connect the bv4111 with 3.3 and GND, and then I supply the optos with the 5V of the Pi ( like now ), and then I connect with an external power supply the GND and JDVcc of the board, will it works without problems?

If they need less than 500mA, i can supply the JDVcc directly through a USB cable connected to the Hub, isn't it?
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Antivirusvivente
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Re: The Right Power Supply

Thu Apr 18, 2013 2:33 pm

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?
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Re: The Right Power Supply

Fri Apr 19, 2013 11:58 am

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?
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 .
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Re: The Right Power Supply

Fri Apr 19, 2013 5:44 pm

No, of course not, I won't. I'm powering only the JDVcc, which means feeding the relays and the second part of the optos. I hope there won't be problems, because a lot of electronic devices work between a range of 4.5 and 5.5v
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