Laser Burglar Alarm -- Need Help

[john1]

We'll get to that.

Are things the same as before, except using No6 instead of No 10 ... ?
and can the 33k reach alright ?

 

[Anonymous321]

We'll get to that.

Are things the same as before, except using No6 instead of No 10 ... ?
and can the 33k reach alright ?

Yes, everything is according to what you have said.

 

[john1]

lovely.

So if we connect the battery, we know what to expect ...
no siren right ?
and can you connect the meter across the siren please

 

[Anonymous321]

Yes, no siren. No voltage reading on the meter, either.

 

[john1]

Okay, you've got the battery on then,
and no meter reading,
and no siren.

thats fine.

now can you take the 33k resistor in your fingers,
and touch it across the No1 and No 6 terminals,
see what the meter does,
Ok

waiting, John

 

[john1]

Oh, and take it off again.

 

[Anonymous321]

When I connect the resistor, the siren rings. And the voltmeter moves.

 

[john1]

hope it didnt sound for too long,
dont want to disturb anyone.

did the meter move the full voltage, or just part of it ?
hopefully the full amount

John

 

[Anonymous321]

Yes it moved the full amount (on the 10V range). My mom was disturbed (she was trying to sleep) but she came and asked me if I needed help. She also thanks you for helping me out.

 

[john1]

Oh dear,
maybe we should leave it for now.

You are nearly done anyway,
it just remains to see if a higher value works as good
(just by touching higher values across)

then connecting the sensor from base to neg.

You're nearly there, but maybe we should leave it for now....

John

 

[Anonymous321]

Well I was hoping that I could get this done tonight. Because I have to prepare for the presentation and have some math tests happening this week too for which I haven't opened my books yet b/c of this. My mother doesn't mind. But yeah, you probably need to sleep. May you please just tell me what I need to do exactly then?

 

[john1]

I am happy to carry on, but i dont want to disturb people

 

[Anonymous321]

I don't mean to sound inconsiderate of my mother's feelings or anything but she's ok with it. I've closed the door of my room. She's not sleeping yet anyway, I believe. I think she's reading a book. And my brothers...well nothing seems to wake them up.

 

[Anonymous321]

If it's ok with you (if you're absolutely sure), I would love to carry on too.

 

[john1]

try a fifty k,
try an eighty k,
you should get to one thats a bit high,
and the meter doesnt read right quite as much,
then go back to the last one that was Ok on the meter.

Maybe you could muffle that siren?

Then we connect the sensor across between the base and neg,
be ready with a light to shine on it ... to stop the siren.

 

[Anonymous321]

I have a 47k and a 100k. I think I may have 70k. It wasn't part of the resistor packs but my cousin who gave me this box had some resistors in it and I determined the ohms they have. And so unless I'm colour blind and can't do math, I think I have a 70k in there. I'll try the 100k too though b/c who knows how long that supposed 70k has been in that box and if it even works anymore or not?

 

[john1]

Briefly:
when you introduce a small current from the base, through the resistor
you're touching onto it to pos,
then it opens the path though between emitter and collector,
which is where the siren is placed.

So the emitter feeds the base, and the collector.
I doubt that you will be asked to explain the action,
but you never know.

 

[john1]

Resistors don't really have a shelf-life,
they might break down in use, but not in a packet or a box.

 

[john1]

did you try the 47k ?

 

[Anonymous321]

Yeah, after this is done, I'm definitely going to have to go through the whole logic behind it and ask you more questions . Of course, that will probably be later on today after you've slept and I've come from school. But thanks for the info there too. It helps.

I'm trying the 47k.