[TriEmbed] One final question regarding my solenoid project

Scott Hall scottghall1 at gmail.com
Sun Nov 3 17:18:29 CST 2013


I would.  I would also disconnect the Vcc line to R1 from the on-board Vcc and
instead connect it to the R'Pi's Vcc line.

That relay board is designed to work with the more tolerant Arduino 5V I/O pins,
not the delicate 3.3V R'Pi GPIO pins.  Separating the optoisolator's input from
the rest of the board keeps the R'Pi's outputs from driving anything but an LED.

I've got an almost identical 4-relay board from SainSmart
(http://www.amazon.com/gp/product/B0057OC5O8/ref=oh_details_o03_s00_i02?ie=UTF8&psc=1)
same schematic per channel, and that is how I got mine to work safely.

On 11/03/2013 05:40 PM, Lucas Rumney wrote:
> So in order to use this board, I would desolder the surface mounted R1, and
> put in its place a normal thru-hole 120ohm resistor if I wanted to keep the
> LED there? 
>
> It would be easier to just keep the LED there, right? so I dont have to
> desolder it too? 
>
>
> On Sun, Nov 3, 2013 at 5:10 PM, Scott Hall <scottghall1 at gmail.com
> <mailto:scottghall1 at gmail.com>> wrote:
>
>     Excellent catch for newby.  It is by no means the only way to approach the
>     problem, but a very effective one.
>
>     The 2mA draw of the LED in the optoisolator is well within the GPIO pin
>     specs of the Raspberry Pi.
>
>     However make sure that you use a separate 5V supply to power the relay
>     board, but you can power the opto- LED from the R'Pi's 3.3V power if you
>     use a 470ohm resister (R1) instead and forgo the extra LED (IN1), or use a
>     120ohm resister if you keep the extra LED.
>
>

-- 
Scott G. Hall
Raleigh, NC, USA
ScottGHall1 at GMail.Com

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