transistors

Stompa

superscaper wrote: »

Not usually but strange the OP should use the term unless they got it from somewhere.

Who knows, but for such a small bit of circuitry I doubt there would be much point - other than making life more difficult for yourself!

Wig

penrhyn wrote: »

In your circuit diagram the pin 1 is the base, pin 2 the emitter and pin 3 the collector.

Exactly, but in this link for a BC546 Pin 1 is the collector pin 2 the base and pin 3 the emitter, and the data sheet is the same, so is the circuit wrong?

And what I really don't get is that the maplin cat said it was a T092 and the layout they gave for the T092 was BCE (which matches the circuit 1Base but the other 2 don't match - in the circuit 2E, 3C) They also had some other T092 designs like T092a T092oa and stuff like that but as far as I could tell the BC546 556 were just T092 (the maplin link shows this too).

Maplin is too far away for me to go and check again, I need to know how to test which pin is the base please. and there's no way to test for collector/emitter?

The outward arrow tells you they are NPN devices.

The 556 is PNP.

Can't quite understand why you have referred to surface mount devices as these are all through hole packages.

Because, I said I don't know my !!!! from my elbow with this stuff.

Superscaper,
Tell me you followed the link of the circuit diagram URL to discover what the circuit was for? Or are you so :cool: that you just knew?

superscaper

Wig wrote: »

Superscaper,
Tell me you followed the link of the circuit diagram URL to discover what the circuit was for? Or are you so :cool: that you just knew?

That would be telling.

espresso

Wig wrote: »

Exactly, but in this link for a BC546 Pin 1 is the collector pin 2 the base and pin 3 the emitter, and the data sheet is the same, so is the circuit wrong?

No the circuit is not wrong. The 1,2,3 are simply labels but what is important is that 1 = Base, 2 = emitter and 3 = Collector.

And what I really don't get is that the maplin cat said it was a T092 and the layout they gave for the T092 was BCE (which matches the circuit 1Base, 2C, 3E) They also had some other T092 designs like T092a T092oa and stuff like that but as far as I could tell the BC546 556 were just T092 (the maplin link shows this too). So if the circuit is wrong, it's a huge coincidence that the Maplin cat is also wrong but also that it matches the circuit, or that I somehow read the cat wrong in a way to match the circuit.

Transistors come in various different packages e.g. TO92a, TO92b, TO92c etc. with different pinouts.

Maplin is too far away for me to go and check again, I need to know how to test which pin is the base please. and there's no way to test for collector/emitter?

See here

The 556 is PNP.

Because, I said I don't know my !!!! from my elbow with this stuff.

Superscaper,
Tell me you followed the link of the circuit diagram URL to discover what the circuit was for? Or are you so :cool: that you just knew?

So why do you not need the RTS (Request to Send) part of the circuit?

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

Fifer

Stompa wrote: »

I wouldn't have thought so for a home-made project.

SMT stuff is becoming more popular for home projects. More and more new devices aren't available in DIL packages. I've used quite a few SMT packaged ICs in audio stuff I've built. It just takes a steady hand and a fine tipped iron.

Wig

So why do you not need the RTS (Request to Send) part of the circuit?

Because it's optional in the ISO standard and I have checked my car does not have a wire on pin 15. So it makes my life easier. Most ECUs don't need to be woken up by an RTS, they start sending straight away as soon as they are able to.

espresso

Wig wrote: »

So why do you not need the RTS (Request to Send) part of the circuit?

Because it's optional in the ISO standard and I have checked my car does not have a wire on pin 15. So it makes my life easier. Most ECUs don't need to be woken up by an RTS, they start sending straight away as soon as they are able to.

Get your soldering iron out then and see if it works!

Wig

I will do, but I still need to be as sure as I can that I read the Maplin catalogue wrong (or the info just was not in there in the first place).

Please confirm that

When viewed flat side up as in the pic, are the terminals always called 123 from left to right? If they are then there is some confusion (with the circuit). If they are not, and as you say not important just labels, can anyone else confirm that?

How do I test for the base?
Is there no test for emitter & collector?

bookduck

Since you are unsure what you are doing, you could have got the ready made thing for about £16 inc p&p via ebay. And it has all the right connectors too

http://cgi.ebay.co.uk/VW-OBD2-RS232-Diagnostic-Scanner-Interface-Tool-Audi-A3_W0QQitemZ290236861265QQcmdZViewItem?IMSfp=TL0806070914a11693

Stompa

Fifer wrote: »

SMT stuff is becoming more popular for home projects. More and more new devices aren't available in DIL packages. I've used quite a few SMT packaged ICs in audio stuff I've built. It just takes a steady hand and a fine tipped iron.

Yes, but there's little point in going down that route unless you really have to.

And in this particular case, it looks as though the intention was to mount all the components directly on one of the connectors:

http://hem.passagen.se/tomasf/obd2/