2
\$\begingroup\$

I am working on a project that requires an Arduino Uno to activate a safety mechanism using 120 V AC from a power supply.

  1. Is the following diagram correct, and are there items (such as a buffer/driver) that are missing?

    Circuit Diagram

  2. What do I need to know to select the correct MOSFET switch?

  3. General advice to keep in mind.

\$\endgroup\$
7
  • 6
    \$\begingroup\$ No, a MOSFET won't work for AC and you'd be wise to add galvanic isolation between the 120V AC circuit and the low voltage Arduino. Consider a relay, for example. \$\endgroup\$ Commented Jan 6, 2022 at 21:56
  • 2
    \$\begingroup\$ Generally when interfacing a low-voltage digital circuit with mains you'll want isolation through an optoisolator or similar device. The circuit you've posted won't work. Do you have a datasheet for the safety device? \$\endgroup\$
    – vir
    Commented Jan 6, 2022 at 21:58
  • 6
    \$\begingroup\$ I can smell the smoke from here already ... \$\endgroup\$
    – brhans
    Commented Jan 6, 2022 at 22:17
  • 3
    \$\begingroup\$ Can you be more specific about the nature of the risk this device will be protecting? If there is a risk of non-reversible injury (lost of life or amputation, etc.) then the design requirements change significantly. \$\endgroup\$
    – Transistor
    Commented Jan 6, 2022 at 22:25
  • 5
    \$\begingroup\$ There are ready-to-use modules with a relay that are easy to use with an Arduino and that will provide the isolation that is needed for safety reasons. Start reading here: randomnerdtutorials.com/guide-for-relay-module-with-arduino You WILL blow things up if you implement the schematic that you show. Also you WILL get sparks and electrical shocks as well. So just use the relay module. \$\endgroup\$ Commented Jan 6, 2022 at 22:32

3 Answers 3

1
\$\begingroup\$

Use a relay module instead: safe, isolated, works with AC.

https://www.google.com/search?client=q=Arduino+relay+module

https://www.amazon.com/Arduino-Relay-Module/s?k=Arduino+Relay+Module

Typical relay module

\$\endgroup\$
1
  • 3
    \$\begingroup\$ For beginners, this is the best choice for a cheap solution to switching AC loads. They are offered in many sizes up to 8 per board and double insulated with opto interfaces. But users should be aware of arc noise when switching off and use twisted pairs to loads. \$\endgroup\$ Commented Jan 6, 2022 at 22:54
0
\$\begingroup\$

That does look terribly bad. You’re inputing 120 AC directly into Arduino, which means Arduino will blow up. Not sure if “Safety Mech” (what exactly is that?) will drop voltage and current, but otherwise 120 VAC doesn’t normally go into a MOSFET gate.

As others have said, just use a relay board. It usually has an optocoupler to separate mains AC from Arduino’s low voltage DC.

\$\endgroup\$
0
\$\begingroup\$

All due respect , the 110 volts going direct into the Arduino ( twice,one straight connection and one via 10k resistor ) remember , the resistor limits current , but you might still have ( high current), it all seems a bit odd to be honestly generous . Also , on the load side it shows + 120 and - 120 vac volts , I am not being mean but I would suggest “ neutral” and “ Hot” Regards

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.