Laser Burglar Alarm -- Need Help

[john1]

Hi Torben,

You've obviously seen these spring things before then.
So i assume its a recognised way of throwing together a bunch of components ?
Just that i dont recall anything like that.

This poster does not seem to have an 'in depth' knowledge of electronics,
so i thought, lets go one step at a time, and get a transistor to work the siren.

Then we can move on to getting it controlled by the sensor.

If it can be done with one transistor, that makes it a little easier.
The siren is around 10 mA, so maybe one will do.

If it needs two then thats more springs i suppose.

So,
Go for simple first, yes ?

John

(and we'll take care of the polarity too)

 

[Anonymous321]

Ok guys. I'm gonna go eat. This camera's giving me grief right now. It didn't even come with a memory card! I thought I'd just be able to plug the usb into my comp and take pics and they'd be stored on the comp...

 

[john1]

Catch ya later

 

[Torben]

Hi Torben,

You've obviously seen these spring things before then.
So i assume its a recognised way of throwing together a bunch of components ?
Just that i dont recall anything like that.

Yep, I first used one about 27 years ago or so. For prototyping or testing I generally use a breadboard, though.

This poster does not seem to have an 'in depth' knowledge of electronics,
so i thought, lets go one step at a time, and get a transistor to work the siren.

Then we can move on to getting it controlled by the sensor.

If it can be done with one transistor, that makes it a little easier.
The siren is around 10 mA, so maybe one will do.

If it needs two then thats more springs i suppose.

So,
Go for simple first, yes ?

John

(and we'll take care of the polarity too)

By all means, take it at whatever speed you like. The Darlington pair should only take 1 extra spring (to connect Q1's emitter to Q2's base); the other springs would probably be shared. You're right that the circuit doesn't require a Darlington, but I've found that using just a single 3904 or 2n2222-type doesn't work nearly as well.


Torben

 

[john1]

Hi Torben,

I agree, of course a darlington or additional Tr in cascade would be a much sharper
change of state, and would be an appropriate way to build such a unit.

However this is a demo, the poster may get the tutor pointing at a component, asking
whats this for, and so on.
So if it can be as simple as possible then the poster should be able to cope.

It is to be presented on Wed, and judging by an earlier post, this tutor can be a
little sharp with the students.

John

 

[Anonymous321]

Ok I'm back with a functional camera. Gonna take my pics right now. And read all those comments you made. Please don't leave!

 

[audioguru]

Just think what would happen if we shorted a mains powered light to turn it off! Horrors.

 

[john1]

Hi,
If you're going to knock up that transistor and siren i posted earlier,
then please show a photo if you can, before energising it.

(just in case)

John

 

[Anonymous321]

Here are some pics. These are the pics of what I originally had. I'm going to try what you guys have been suggesting I guess. And thanks a lot again by the way.

 

[Anonymous321]

And Torben. My laser is just a normal laser. It has 5mW of power. The 28.5V junk was my confusion over the transistor needing 30V so I'd have like 19 AA batteries supplying 28.5V and the laser supplied the rest. So when it broke, there wasn't enough and the siren would go off.

 

[john1]

The pics are fine.
Any chance of one from directly above the springs. ?

John

 

[Anonymous321]

Umm sure. Well I was making that small circuit you advised me to before. So it's kinda disassembled. Should I still take them nonetheless?

 

[john1]

just one from above is all i want.
please carry on with the circuit you're doing.

Cheers, John

 

[john1]

how's it going ?

 

[Anonymous321]

I believe I got it right. I must admit that I am a little confused as to the connections. I mean...+ve of battery to +ve of siren? But anyway, this is what it looks like with that circuit you advised. The pic from above is coming. The one I took right now was too big for this forum. -_-;

 

[Anonymous321]

So when I try uploading pics...

"There seems to have been a problem with the Electronic Circuits Projects Diagrams Free database. Please try again by clicking the Refresh button in your web browser.

An E-Mail has been dispatched to our Technical Staff, whom you can also contact if the problem persists.

We apologise for any inconvenience."

...............

 

[john1]

Oh well,
I will attempt to work with whats there.

Have you put that circuit together ?

 

[Anonymous321]

Yes, I have. I have a pic of it in a previous post. It's called "6". And I think it's just the size of the pic that's causing this. When I shoot a bird's eye view of it, the pic size is bigger than the other views.

Edit: Wait..that pic. I can't really see it.... Have you just rotated pic "6"? Or made your own?

 

[Anonymous321]

Ok got it. I had to bring the camera in a little. I hope you can understand it.

 

[john1]

super .......