Small relay for logic pourpose


What's the best option to match a logic gate? I mean, what i need to archieve is just a shorcut on the output (just an open/close circuit)

As far as i know, using a DIL05 relay will fit my pourpose as this kind of relays already have the diode inside. I don't need to amplify thru a transistor becouse the arduino pin out handles the small current needed to latch the relay. (At least is what i think, i haven't tried yet)

I also want to connect it to a GPI (general pourpose interface. You can find in a lot of pro audio equipment), what is something very similar from above, i think.

Anyone has used those tiny DIL05 with the diode inside and without the transistor?
And what about the GPIs?


Anyone has used those tiny DIL05 with the diode inside and without the transistor?

Do you have a datasheet for the relay; that will give you the information on the current draw for the coil - if it goes above 40ma, then you are going to need a driver transistor or something, because the Arduino won't be able to handle it.

There is another good reason why you should always use a driver transistor or IC for such loads, even though they may be spec'd within the parameters of the processor (or other circuit) being used; relay coils can and do fail - usually they will fail "open", but they can also develop a short, which can result in a much larger current draw. With a driver transistor or such in place, you will blow that part before you blow the pin on the Arduino or other controller.

It depends on whether you want to replace a "5 dollar part" or a "5 cent part", when that occurs...



Thank you for the info... and yep, you are right about the transistor.

What it seems better for my project is the GPI i'm interfacing to seems to accept without any bad symptom a direct connection between the arduino's digital pin (5v) and the GPI pin. So... the transistor will be there on the final PCB, for sure, but for this very early sketch, it's something easier.

Thank you again.

I don't know anything about GPI, but it could be a simple 5V TTL interface, in which case (as you have seen), nothing bad should happen to the Arduino end. If you wanted some protection, though, using a non-inverting buffer or an op-amp on the pin would help (it would be one-way only, though).

I just did a quick look on a piece of pro-audio equipment with GPI, its manual stated that GPI is a digital input in which "1" is represented as 3 volts to 24 volts, and 0 is ground.

This should be OK as long as you are transmitting from the Arduino to the GPI interface, but if the GPI pin from the audio equipment tries to send data out that pin, at greater than 5 volts, that pin on the Arduino (and possibly the Arduino itself) is toast.

I don't know if the GPI "bus" is bidirectional, or whether certain pins can be set as input vs. output only - ie, how much control the end user has; as well as whether each piece of equipment has a set use for the pins, or what they are for...

Just fair warning for what you are doing...good luck!