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.

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john1

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

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john1

did you try the 47k ?

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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 :P. 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.

john1

if its legs are long enough,
just touch it on

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john1

it might sound the same on the siren,
but check with the meter,
if its alright there

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Anonymous321

Well the meter reading for the 47k seemed the same as the 33k. But as for the sound difference, the 33k gave more sound. This is opposite to what you just said....I'll try again.

john1

must have just arrived at pretty much the right value,
if a higher value makes a difference.

So next is the sensor.

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Anonymous321

Ok, should I put the photocell on no4 and no5? One wire going from no1 to no4? And then another wire going from no5 to no21 (which is -ve of 9V)?

john1

The sensor would go between 1 and 3 terminals.

Have a torch or laser light ready, to quieten it,
or be ready to flick off the battery connector.

And i would like to see that sensor a bit better,
it might be polarity concious.

Any markings on it?
Or is one leg distinctly longer than the other,
thats another way they show polarity sometimes.

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Anonymous321

Ok, I'm taking more pictures of it. I don't think one leg is longer than the other.

So you want me to put the photocell on the base and the emitter then?

Well I'm going to do that after I post some pics of it for you.

This is the link for it:
http://www.thesource.ca/estore/Produ...roduct=2761657

john1

Okay,
then you're pretty much done.

The resistor that you settled on should be high,
but not so high as to start affecting the output.

that has to go on too.

Once its all together,
it will only be quiet if light shines on the sensor.

So have a torch ready, or be ready to flick off the battery.

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john1

I had a bit of a look at that sensor on an earlier pic,
i couldn't see any polarity to it.

See what you think.
I dont think it would harm it, if it was polarised,
and got connected backwards, as its only on the base-emitter junction.

But it doesnt look polarised.

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Anonymous321

Well I can't get any good pics of the photocell. I hope you were able to see it. Here is what the top basically looks like:
http://www.futurlec.com/Pictures/Photocell.jpg

So now I have to:
- photocell on no1 and no3. It doesn't matter which lead on what terminal right? B/c I can't seem to tell a difference in the lengths.
- resistor ATTACH on to no1 and no6?