Isolated 5V-to-12V Relay Driver
Budget: ₹600 – ₹1,500 INR
I’m putting together a small interface that lets a 5 V logic line drive a 12 V DC mechanical relay while keeping the control electronics completely isolated from the field wiring. My plan is to repurpose an off-the-shelf two-channel relay module for the load side and pair it with a standard optocoupler breakout on the control side; you can choose whichever optocoupler best meets the brief as long as it fits the isolation goal.
What I need from you is a concise, ready-to-build circuit design:
• A clear schematic showing the 5 V input network, the optocoupler stage, any necessary current-limiting or pull-down components, fly-back diode protection for the 12 V coil, and the wiring to the relay board.
• A bill of materials with exact part numbers so I can order everything immediately.
• A short design note (a page or two is fine) explaining the current calculations, isolation boundary, and how the transient suppression is handled.
My microcontroller pin can only source a few milliamps, so please size the input resistor accordingly. If you can include oscilloscope screenshots or a quick SPICE plot verifying clean switching, that would be a nice bonus but it’s not mandatory.
Looking forward to a straightforward, well-documented solution that I can drop straight into my build.
What I need from you is a concise, ready-to-build circuit design:
• A clear schematic showing the 5 V input network, the optocoupler stage, any necessary current-limiting or pull-down components, fly-back diode protection for the 12 V coil, and the wiring to the relay board.
• A bill of materials with exact part numbers so I can order everything immediately.
• A short design note (a page or two is fine) explaining the current calculations, isolation boundary, and how the transient suppression is handled.
My microcontroller pin can only source a few milliamps, so please size the input resistor accordingly. If you can include oscilloscope screenshots or a quick SPICE plot verifying clean switching, that would be a nice bonus but it’s not mandatory.
Looking forward to a straightforward, well-documented solution that I can drop straight into my build.