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Short Version: How to connect (Which Terminals Go Where) the following two components

  1. DRDC3105 (A relay driver)

relay driver diagram

  1. SRD 03VDC SL C (A 3V relay supposed to control the flow of 230V AC and controlled by esp32)

relay example

Longer Version :) I'm a beginner trying to build a smart plug using esp32. The Analog Power schematic is a bit confusing for me.

I've decided to go with SRD 03VDC SL C Relay and am searching for a reliable schematic to control it with esp32. I've found some circuits with implementations using transistors and some with relay drivers like DRDC3105. But they are all for somewhat different applications and use different components. So I'm not sure they'll work in my situation.

I just need to make sure whether using relay driver is a good idea for this project, since I'm printing a PCB for it also. If so How to connect the DRDC3105 to SRD 03VDC SLC?

References:

Relay: https://www.lcsc.com/product-detail/Relays_SRD-03VDC-SL-C_C24585.html

Relay Driver: https://www.lcsc.com/product-detail/Gate-Drive-ICs_Diodes-Incorporated-DRDC3105F-7_C460721.html

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  • \$\begingroup\$ Can you write a specific question? \$\endgroup\$
    – Voltage Spike
    Commented Jul 13, 2023 at 19:49
  • \$\begingroup\$ I'm sorry you weren't able to get my specific question. It was about whether Using a relay driver is actually a good idea for this project if so how to connect it with a relay driver? I've skipped the usability of relay driver in the summary of the question. I don't know what else I have to be specific about. I'll try my best to rewrite it. Sorry. \$\endgroup\$ Commented Jul 14, 2023 at 7:02

1 Answer 1

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Yes, that should work. The relay datasheet does not cover the 3V variant, however it should draw around 120mA ('L' version => 360mW). Suggest you set the ESP32 output to maximum drive.

You could also use a jellybean MOSFET and a couple discrete parts (diode and resistor). The relay driver shown is more expensive and requires more drive current but it will reduce parts count and may increase relay lifespan.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Thanks @Sphero for the immediate reply. I would like to know which terminals should be connected to where. Like the out of the Relay driver should go into one input of the relay right so then both the grounds (one in the relay driver and the out of the electromagnetic coil in relay) should be the same? And how exactly can I set the esp32 output to maximum drive. Sorry if that's a dumb question but I'm still a beginner \$\endgroup\$ Commented Jul 13, 2023 at 19:36
  • \$\begingroup\$ See the above schematic and refer to the datasheets of the relay and driver. For configuring the ESP32 output, that's outside of the scope of this answer. Also outside the scope is layout- the grounds of the driver and ESP32 are common. \$\endgroup\$ Commented Jul 13, 2023 at 20:01
  • \$\begingroup\$ Thank you very much for the answer. I need a small clarification @Sphero. Sorry if this is dumb. But shouldn't we have a flyback diode parallel to the relay. and the D1 in the relay driver is the flyback diode isn't it? Or does the relay driver use some other mechanism to avoid spike caused when turning it off. \$\endgroup\$ Commented Jul 14, 2023 at 7:45
  • \$\begingroup\$ The relay driver has a Zener diode inside it which performs a similar function. In fact it lets the relay drop out a bit faster than if you put a diode across the coil, which is generally a good thing (but is a bit harder on the driver transistor). So no, you don't need to add a diode across the coil if you are using this driver. \$\endgroup\$ Commented Jul 14, 2023 at 12:10
  • \$\begingroup\$ Thanks a lot for that clear clear explanation. \$\endgroup\$ Commented Jul 16, 2023 at 16:11

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