[TriEmbed] Driving 32 5v relays

[Rodney Radford]

I agree with Adam that the new digital LED strings are a lot of fun and you
should investigate them.

However, if you want to use relays, try something like this as it has the
builtin drive transistors for each relay:

http://www.dx.com/p/arduino-compatible-16-channel-5v-relay-module-expansion-board-white-143789#.VafOGPlViko

On Thu, Jul 16, 2015 at 11:25 AM, dan via TriEmbed <triembed at triembed.org>
wrote:

> You might also need to check that the chip you're using can supply that
> current on each pin. From the datasheet, it looks like the outputs can only
> supply 25-35mA each. To get around this limitation, you could use a
> transistor and have each pin drive the transistor instead of the relay
> directly.
>
> -Sent from my phone
> On Jul 16, 2015 11:17 AM, "Adam Haile via TriEmbed" <triembed at triembed.org>
> wrote:
>
>> Stupid question... why not just use digital LEDs?
>> https://www.youtube.com/watch?v=_nbuSgYoCSQ
>> Full disclaimer: I have a tiny business that does LED lighting stuff, but
>> I am also just a huge fan of digital LED strips since they take away
>> complications like those with relays and such.
>>
>> More on your original question... no, no... not a resistor to do 14v ->
>> 5v! You would be dropping 9v and @ 3A be dissipating 27W!   I have bins
>> full of buck converters like the one linked below that will do 8-23V input
>> and output a nice steady 5V. They work great and are very efficient.
>>
>>
>> http://www.amazon.com/Nextrox%C2%AE-Display-Supply-Converter-Module/dp/B00CBCGAL8/
>>
>> On Thu, Jul 16, 2015 at 11:10 AM, Richard Prevette via TriEmbed <
>> triembed at triembed.org> wrote:
>>
>>> I am making a Christmas light display using 32 relays.  Using arduino
>>> and four 74HC595n shift registers.
>>> The relays are SRD-5vDC-SL-C.  Here is the question: I may be
>>> misunderstanding but the datasheet states each
>>> relay takes 72ma.  I put  a meter across the power and that seems
>>> right.  At one point all relays will be on at the same time.
>>> That looks like I need a power source that will supply about 2.3 amps.
>>> 32 x 72 x 1000 = 2.3a (Correct ?)
>>>
>>> I have a Dell AC adapter that states output at 14v dc and 3 amps.  All I
>>> need is a resister to lower 14 to 5 volts and
>>> I good to go?
>>>
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>>>
>>
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>>
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