Hi All,

Just want to say I am just a hobbyist with electronics, and it's been a while since I have had to use Ohm's law, etc... so please bear with me.

I am trying to figure out what's the best method to drive a DPDT 5V relay using a TTL level signal (0v = OFF / 5V = ON)

This is the relay I want to use to switch analog line-level audio signals.

Panasonic TQ2-5V
Coil Res = 178Ω
Coil Current = 28.1ma
Relay Datasheet

I was thinking of using a component like the Onsemi MDC3105LT1G described as an inductive load driver
Driver Datasheet
It seems like this would work nicely as it basically integrates all of the components I would need to create a transistor-based driving circuit

This is the circuit thus far using the MDC3105, I threw in the switch just for testing purposes if I decide to build it.
The datasheet says you do not need a diode across the coil, but from a lot of reading the consensus seems to be that the circuit would still need one and possibly one on the Vin pin.



and this was my previous attempt at making my own circuit:



I have not tested either circuit, I was trying to get this simulated/tested in software like LTSpice, but need to learn how to use that first.

I have read that mosfets might be a better choice to use much less current than the transistor type circuit would need?

I would greatly appreciate and welcome any assistance/suggestions.

 

Welcome to AAC.

Why do you think you need to add a flyback diode when the datasheet explicitly lists not needing one as a benefit of using the part?

As far as simulation goes, while it is a good idea to learn SPICE as a tool, there’s not really a point in this case. Just breadboard the circuit. The component is intended to make this dead simple and you are making it very complicated.

 

Welcome to AAC.

Why do you think you need to add a flyback diode when the datasheet explicitly lists not needing one as a benefit of using the part?

As far as simulation goes, while it is a good idea to learn SPICE as a tool, there’s not really a point in this case. Just breadboard the circuit. The component is intended to make this dead simple and you are making it very complicated.

I probably am, Spent way too much time reading all types of posts on this matter. I will order some MDC3105 to test with.

 

I probably am, Spent way too much time reading all types of posts on this matter. I will order some MDC3105 to test with.

Sounds good.

If you fry one, well, that’s how you learn sometimes...

Have fun.