optically-triggered auto-off circuit

[OP No.1166773]

I am trying to design a circuit that will allow an appliance to stay connected to wall power in the US only as long as a LASER shines onto a photosensitive element on the circuit, using a solid-state relay.
The control circuit itself is wall-powered through a voltage regulator.

The plan is to eventually get the control circuit printed onto a PCB and the whole thing (with the relay and regulator) in a project box with the LASER diode, switches, photosensitive-resistor, and connections to wall cable and appliance attached.
I dunno much about circuit design so I came to /diy for feedback about effectiveness and safety of my design.
Any feedback would be appreciated.

Thanks, /diy/

[OP No.1166775]

about the image, I can't take screenshots, for reason

[Anonymous No.1166779]

>>1166773
7812 isn't going to take 120vac, well, not for long anyway!
the relay kind of shorts out the src, did you mean that?
d1 is doing nothing for an optical relay?

check this for simplicity, swap ldr with pot for inverse action

[OP No.1166788]

>>1166779
Sorry if I may not have gotten all of that, I'm not too familiar with this, so I'll try by best to understand...

I'll trade 7812 for a different regulator in that case.

Not totally certain what you're referring to be 'src' being shorted by the relay (sorry, I don't know circuits that well). I was just thinking the relay would operate the triac based on whether there was a voltage drop between the relay's anode and cathode inputs.

I'll remove d1... Not sure why I included it now...

As far as swapping the ldr for a pot, I'm assuming you mean a potentiometer? Wouldn't my circuit need a light-dependent resistor to do what it's supposed to?

In any case, thanks for the help!

[OP No.1166795]

I just noticed I'm powering my laser diode from the +12V input to my control circuit, which I'm wondering might just shunt almost all the current through there and leave nothing to power said circuit...

[Anonymous No.1167535]

re bump if anyone has any more input maybe

[Anonymous No.1167538]

Hi zaber linear stage with windows 98 anon.

Have you verified that cutting mains from the linear stages is safe? And that restoring that power will not generate a surge?

[Anonymous No.1167551]

>I'll trade 7812 for a different regulator

Regulators won't cut it, you need a whole AC-DC thing.

[Anonymous No.1168402]

>>1166773
There is just so much wrong with this circuit.

See how the load is never going to be fully turned off because you have what reduces to a series loop that includes your load, a 100 ohm resistor and a capacitor? The ac power will always be flowing through this loop. The corner frequency is going to be around 160 hz, but there will still be some juice flowing.

You have ac power going in to a DC regulator. That is enough to kill any regulator in a matter of microseconds.

You are using the ac neutral line as the ground for the DC side of the circuit. You will definitely destroy your DC component this way, and especially your laser diode.

Speaking of the laser diode, you need a constant current supply to power that correctly. If you just apply 12 volts dc, you will fry the diode in, again, microseconds.

Are you the same guy that wanted to build a limit switch for a moving linear stage? This is definitely the wrong way to go about it. I think we already mentioned in the last thread that all you need is a simple limit switch. If you are absolutely dead set on using a laser, which just makes this 100X more complicated, then use a laser tripwire that doesn't involve the stage moving the laser beam. Also, just use a simple circuit for the tripwire instead of all this unnecessary crap. The more complicated you make this, the more likely it will not work.

[Anonymous No.1168421]

>>1168402
This guy again. Pic related is the simplest and most reliable way to do what you want to do. If you absolutely 1000% *require* that a laser is somehow installed, I'll draw up another circuit for you, but I really think that this is all you need.

[Anonymous No.1168461]

>>1168421
thanks very very much, for the input.
I do need the laser shutoff, it's for a project I'm helping someone more clueless than me with, and I'd definitely appreciate more advice of any kind, but either way, thanks a bunch for what you've already given me to think about.

[Anonymous No.1168486]

>>1166773
...w..why? A timer or a clapper isn't good enough? bluetooth paired with your phone? why a laser?

[Anonymous No.1168510]

>>1168486
no i need a light activated auto off, this is what is required of me >:|

[Anonymous No.1168513]

>>1167538
good question and no

>>1167551
like an adapter?

[Anonymous No.1168529]

>>1168486
>>1168510
Just wire up a Clapper to it and throw in some photoresistors and relays here and there. When you're asked to fire up the laser, do it, then start clapping. If asked why you are clapping, just say how you're overjoyed that the whole thing works splendidly.

[Anonymous No.1169612]

>>1168461
Bumping because I will come back with a schematic for the laser setup. Just dealing with family issues over the last couple of days.