Non insulated TRIAC control circuit

I planed to design a awesome iot product to remotely switch my home AC appliance ON and OFF. I have selected the ACST4 over voltage protected AC switch from STMicroelectronics and negative power supply method where control circuit voltage supply +VDD is connected to COM terminal of ACST4 and its gate will be connected to bc547’s collector end through a current limiting resistor its emitter will be connected to the VSS of the control circuit as the ACST4 triggering circuit and the npn transistor base emitter current will be given through a GPIO pin of a micro controller present in the control circuit. it would be very helpful if you solve the following doubts

  1. whether this type of non insulated TRIAC control circuit is safe for the low level DC components present in control circuit or the components will get damage during inductive load surge and line transient
  2. There is no galvanic isolation between AC line and DC. is it safe to touch the DC components present in control circuits
  3. When i ask this to other people they are saying that how can connect your 5v dc to neutral terminal of a AC, your circuit will blow up
  4. i tried this circuit it is working fine but all are saying this will fail by time
  5. it will be greatly helpful to me if you correct me if i did anything wrong, suggest any tips for improvement of this circuit

****** i have attached my circuit diagram, ACST4 data sheet and its APP note where i found this type of triggering circuit for your reference*******

acst4.pdf (378 KB)

How to select the Triac, ACS, or ACST that fits your application.pdf (364 KB)

You have zero appreciation for the lethality of mains voltage. Your design is a time bomb waiting to hurt or kill someone.

A triac output optocoupler is how you drive line connected triacs, not with a transistor.

I understand what are you trying to say but plz explain how and where it will fail so that whomever read this post will not repeat the same mistakes in any way. It also more helpful if you explain then why the stmicroelectronic suggested this type of triggering circuit in their App note or if I have wrongly implemented it then suggested the right way to do it...

I’ve already told you how to properly interface to a triac. Goggle “triac mcu interfacing” and do some research if you believe otherwise.

ST is trying to sell the features of their device and the people responsible for the ACST4 datasheet, specifically figure 17 on page 7, are marketing idiots. No one with any experience would build such a circuit.

@avr_fred suggestion are helpful. If some one can explain technically what and why it will go wrong in the mentioned type of triggering circuit it will be much more helpful

Why can't you use a relay or SSR to switch mains powered devices on/off, like everybody else does.
Leo..

OP’s circuit:
IMG_20180512_174111.290.jpg

If some one can explain technically what and why it will go wrong in the mentioned type of triggering circuit it will be much more helpful

You appear to have zero understanding of what you’ve built. Discussing the triggering circuit is pointless and irresponsible as that is an incredibly dangerous circuit. What can go wrong is that you or anyone else that comes into contact with what would normally be a safe to touch 5 volt mcu circuit is now a lethal shock hazard.

You do not understand the implications of what you’ve built. It is not a question of if that circuit will blow up, only when. If you persist, it will only be a matter of luck that you don’t end up killing yourself.

This is not a laughing matter and I will not post in the thread again.

If you build a directly connected triac circuit like this the entire circuit is live and must be insulated appropriately so no part can be touched.

MarkT:
If you build a directly connected triac circuit like this the entire circuit is live and must be insulated appropriately so no part can be touched.

Insulation is of course required but it is not enough in a typical situation. What happens when the circuit has mains power and a desktop pc is plugged in to download code? The common of the ATmega 328 will be grounded through the USB connection.

ZAP. BOOM. POW. when the linear regulator flashes over in a ball of fire. The user will be lucky to escape with only burns on their fingers when the metal housing of the usb cable makes contact with the usb connector. If they happen to be touching the metal of the cable connector, it could be a rather tragic ending

If you connect to it, you’ve cut a hole in the insulation to do so though…