Laser Burglar Alarm -- Need Help - Page 7 - Electronic Circuits Projects Diagrams Free

john1 · 6th May 2008, 02:25 AM

Just to check,
the transistor is the NPN type, yes ?

Anonymous321 · 6th May 2008, 02:27 AM

Quote:

Originally Posted by john1

Okay.
stick your voltmeter across the siren connections,
and connect the battery briefly, then disconnect the battery.

Any siren sound ?
Any voltage show on the meter ?

No siren. No voltage.

Anonymous321 · 6th May 2008, 02:28 AM

Quote:

Originally Posted by john1

Just to check,
the transistor is the NPN type, yes ?

Yes, it is. I'm a little afraid that it may be busted from so much previous use. So I might just pluck in another one.

Anonymous321 · 6th May 2008, 02:31 AM

Is everything going according to plan?

john1 · 6th May 2008, 02:31 AM

dont change anything,
its fine

Anonymous321 · 6th May 2008, 02:32 AM

Quote:

Originally Posted by john1

no, dont change anything

Ok, I won't. Oh ok.

john1 · 6th May 2008, 02:33 AM

could you now pick a resistor, around thirty K please.

john1 · 6th May 2008, 02:35 AM

Ha,
my last post crossed with yours,
and i thought for a minute you were going to pull it apart!

When i edited, i saw you noted my post before i edited !

Anonymous321 · 6th May 2008, 02:36 AM

Quote:

Originally Posted by john1

could you now pick a resistor, around thirty K please.

The closest one I have is 33k. Should it be 1/4 or 1/8 watt?

Anonymous321 · 6th May 2008, 02:37 AM

Quote:

Originally Posted by john1

Ha,
my last post crossed with yours,
and i thought for a minute you were going to pull it apart!

When i edited, i saw you noted my post before i edited !

Haha yeah. Instant messaging.

john1 · 6th May 2008, 02:39 AM

Briefly,
the transistor starts in the off position (not conducting)
until some current through its base will allow it to conduct E to C
so all is well so far.

Now to allow it to conduct we will introduce some current through its base.

Okay ... ?

Anonymous321 · 6th May 2008, 02:40 AM

Quote:

Originally Posted by john1

Briefly,
the transistor starts in the off position (not conducting)
until some current through its base will allow it to conduct E to C
so all is well so far.

Now to allow it to conduct we will introduce some current through its base.

Okay ... ?

Wait! Not yet, please! Did you see my post from above?

john1 · 6th May 2008, 02:42 AM

hard to gauge sizes ...
will the resistor 33K reach from number 1 terminal
to number ten terminal ... ?

Just to touch it on while holding it.

john1 · 6th May 2008, 02:43 AM

dont worry,
battery not on yet ...

john1 · 6th May 2008, 02:45 AM

you mean the wattage .. ?
just use the one with the longest legs.
i don't think we will be driving it hard.

6th May 2008, 02:25 AM	(permalink)
john1 Experienced Member	Just to check, the transistor is the NPN type, yes ? __________________ ************************************************ ***************

6th May 2008, 02:31 AM	(permalink)
john1 Experienced Member	dont change anything, its fine __________________ ************************************************ ***************

6th May 2008, 02:33 AM	(permalink)
john1 Experienced Member	could you now pick a resistor, around thirty K please. __________________ ************************************************ ***************

6th May 2008, 02:35 AM	(permalink)
john1 Experienced Member	Ha, my last post crossed with yours, and i thought for a minute you were going to pull it apart! When i edited, i saw you noted my post before i edited ! __________________ ************************************************ ***************

6th May 2008, 02:39 AM	(permalink)
john1 Experienced Member	Briefly, the transistor starts in the off position (not conducting) until some current through its base will allow it to conduct E to C so all is well so far. Now to allow it to conduct we will introduce some current through its base. Okay ... ? __________________ ************************************************ ***************

6th May 2008, 02:31 AM	(permalink)
Anonymous321 Experienced Member	Is everything going according to plan?

6th May 2008, 02:42 AM	(permalink)
john1 Experienced Member	hard to gauge sizes ... will the resistor 33K reach from number 1 terminal to number ten terminal ... ? Just to touch it on while holding it. __________________ ************************************************ ***************

6th May 2008, 02:43 AM	(permalink)
john1 Experienced Member	dont worry, battery not on yet ... __________________ ************************************************ ***************

6th May 2008, 02:45 AM	(permalink)
john1 Experienced Member	you mean the wattage .. ? just use the one with the longest legs. i don't think we will be driving it hard. __________________ ************************************************ ***************

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