Since I am new here, first I would like to apologize if I did draw this schematic wrong (i.e. lines do cross, etc.). It is a few days that I am using this online editor, so I am still in the learning process and need to gain a bit more experience.

I created followed circuit:555 timer in astable mode that will power up 8 LEDs (blink 4 by 4). When output of timer goes high, first 4 LEDs will be on (it stays on about 0,69 × (1k + 470k) × 2,2 µF), and when output of timer goes low, remaining LEDs will be on (0,69 × 470k × 2,2 &micr0;F).

At the same time I hook up LED light bulb (10 W) via 5V relay with 230 V mains. Idea is that this LED bulb will light up every time when switch is pressed, and turned off with another switch press.

Current in a circuit is approx. 110 mA

As you can see, I am powering my circuit with PSU: MEAN WELL IRM-01-5. In its datasheet, I can see that it has over voltage protection (OVP), overload protection (OLP), short circuit protection(SCP), but I didn´t find anything about OTP (over temperature protection).

I am assuming that these kind of protections protect only the 5V side, but what is with 230V side?

Since I am planing to put my regulator, PCB with all components, and relay inside a box and it would be human operated, I need it to be safe as much as possible.

So my question are as follows:

  1. How and is there any need to protect PSU from 230 V mains? Fuse, crowbar, …?
  2. Is it smart to protect it with some OTP (overtemperature) device like thermistor or similar?

I am very grateful for any advice and help.

enter image description here

  • 1
    \$\begingroup\$ While there are things I would do differently if I were drawing this schematic, it's certainly nowhere near as bad as a lot of the ones I've seen on here. \$\endgroup\$
    – Hearth
    Jun 8, 2020 at 13:06
  • \$\begingroup\$ "LED bulb will light up every time when switch is pressed, and turned off with another switch press" - The way this is drawn, the LED light bulb will only illuminate while the button is pressed. \$\endgroup\$
    – rdtsc
    Jun 8, 2020 at 13:19
  • \$\begingroup\$ If you want the mains-powered LED to toggle with each button press, you need to get a switch that works that way. \$\endgroup\$
    – Dave Tweed
    Jun 8, 2020 at 13:50
  • \$\begingroup\$ @DaveTweed While that would be the easiest solution, there definitely are ways to do it. I'm sure I've seen a toggle switch implemented with only two or three transistors. \$\endgroup\$
    – Hearth
    Jun 8, 2020 at 13:54
  • \$\begingroup\$ @Hearth: Well, sure. You could even use a second 555 to do it. But that isn't what the question is about. \$\endgroup\$
    – Dave Tweed
    Jun 8, 2020 at 14:00

1 Answer 1


Meanwell produces good quality products (I use them regularly), so additional protections of the type you describe should not be necessary.

But the point has come up in the comments regarding your large LED bulb, and the fact that you want a "toggle" action on the button. The easiest way to do that is to get a pushbutton switch that has the required mechanical action. But if you only have a momentary switch, you can build an electronic circuit to toggle the relay. In fact, you could use a second 555 to do it.

  • \$\begingroup\$ Thank you for your answer.The only reason why this switch is in this place is because i found him first in editor so i placed him \$\endgroup\$
    – Eyeda
    Jun 8, 2020 at 14:30
  • \$\begingroup\$ My bigest concern(lets say so) is overvoltage and overtemperature.If there a fault in neutral wire at distribution side emerge my PSU could expirience voltage more than a 400 V which would probably lead to destruction.Is there any way to prevent this?And second thing is that PSU would be placed in a box,with a max.alowed temp. aprox. 83 celsius and it could be developing higher temperature due closed box. \$\endgroup\$
    – Eyeda
    Jun 8, 2020 at 15:10

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