HEADACHE Transistor Siren Circuit

[AutoElecHack]

Hello,

I'm new here and this is my first post.

My name is Daniel and I'm an Automotive Electrical apprentice and a starting to delve into the smaller electronics such as circuitry, etc.

I have recently purchased a Jaycar Project book with small component kit to put all the projects together and am stuck on a few oscilating circuits atm.

Whether it's the alternating flashing leds, random dice or the siren circuit. The circuit will not oscillate properly.

I did manage to get the alternating flashing leds to run properly by swapping out a resistor for a potentiometer and tuning it down in resistance so they would flashing equally and slow enough.

But I am really getting sick and tired of these circuits not performing how they should, straight off the bat.

I am checking and rechecking my circuits and they are all wired correctly.

So I have just put the below circuit together and all I am getting is a constant tone from the speaker. That is it.

These are the first experiences I have had with transistors and I have always found them the most difficult part of electrical.

The main reason for me is that there are so man different explanations for them that it's hard to keep a solid theory in my head. I don't even bother with my trade teachers as my boss has probably forgotten more than they know and even my boss gets lost in his bullsh**.

If anyone here could help me out that would be great. I hate NOT knowing why something is performing the way it is.

I plan on getting through this project book and then once I have a good solid understanding, moving onto my arduino uno kit that I have sitting here.

[SeanB]

That is correct for that circuit, it only makes a tone.

[Strada916]

that is what i would expect from that circuit, single tone.

[AutoElecHack]

Thanks for that guys.

For some reason in a beginner book they have found it funny to write "It doesn't sound like a siren, that's right-we fibbed"...

So its not a siren it's just an audible signal tone, etc.

If you don't mind I will post up the other kind of circuit I have been having troubles with aswell.

I found this one to flash so fast and dim that both LEDs were nearly on all the time. I did manage to change out the resistor values for some and slow the pattern down a bit more.

[AutoElecHack]

I just burnt myself with a tiny little transistor!

OMG, I never knew they could get so hot by having them powered without a resistor!!!!

So with an NPN transistor, The positive signal on the base will bring the emitter and collector together. It's as simple as that? With the one rule that atleast either the emitter or collector needs to be a negative so as to create current flow? as in turn the transistor on?

So with that said, does that mean that a PNP transistor is exactly the opposite. A negative needs to be at the base and either the emitter or collector need to be positive?

I deal with relays on a daily basis as I'm an apprentice auto elec, I can see a great likeness between the ones I use at work and these transistors. The only main difference I see is that Switching a relay on requires both positive and negative to join your supply and loads and that it runs of electromagnetism, whereas the transistor is simply a composite of silicone or whatever that has been designed accordingly to achieve it's semiconductivity...I can imagine that's not a word!

Any help in getting me on the right track with these fundamentals is greatly appreciated.

[AutoElecHack]

I'm totally stocked that I have worked out how to use a transistor in basic terms. Oh man.

Thanks for the help guys. I should have done this from the start. That is get a good old breadboard and some resistors and an led and hands, watch how changes to the circuit effect different components and in what formation, etc.

During these, I had a thought and put two Diodes in place of the NPN transistor and found that even though it did not have the semiconductivity of the silicon transistor, they still acted the exact same way as the transistor when using direct on and off/switch. Just not when i apply low voltage to base, for example holding a positive lead in one hand and grabbing a lead hooked up to the base in the other. With a transistor the LED would glow dimly whereas with the diodes, there was nothing unless proper connection was made with a conductor.