Upgrades to Audi key

[Nuvo]

The page I linked to gives a link and email contact address for a UK distributer (Young Electronics Group in High Wycombe) and also a link to a German webshop for smaller order quantities.

The webshop also supplies some tiny 10 and 22 µH inductors measuring only 3.2 mm x 2 mm x 2.5 mm for this application too.

HTH Rob.

[HPmuirt]

I happened upon this small outline ASIC which could be the solution to your problem if it can be made to fit inside the internal of the keys body. I'm thinking that it could be placed where you currently have the transistor.

edit: I've just had a quite scan of the data sheet given in the above link. The PR4401/4402 looks perfect for this.

Ah hah, That looks familiar - I remember seeing that some time ago when I started thinking about doing this but I failed to find a UK source and then by the time I got round to doing this I had forgotten all about it and so did it the manual way.

We need to track some of these beauties down.

Cheers n

Si

[Nuvo]

Thanks for the info Si, If you are only using a transistor it must somehow be running as a basic oscillator yes? I wouldn't have expected a transistor to be able run from 1.5v supply. What manner of trickery is this?

I happened upon this small outline ASIC which could be the solution to your problem if it can be made to fit inside the internal of the keys body. I'm thinking that it could be placed where you currently have the transistor.

edit: I've just had a quite scan of the data sheet given in the above link. The PR4401/4402 looks perfect for this.

[newsh]

Circuit diag?

[HPmuirt]

Genius Si.
Sadly, I butchered my light giving key many moons ago to make a flip key.
But wanted the illumination again, so I made this.
I can now find the car from 500 yards away in the dead of night

I to your superior creative skills as ever Jas

That's it Jas, bring the thread down to the level it deserves!

That's it Fatty, you're off my Christmas card list now

I dunno, a man tries to better himself and all he gets is abuse

I guess the only way to please some people is to spend 30 hours cleaning a car with a piece of clay and a toothbrush

Cheers n

Si

[HPmuirt]

I really like what you've done there. Surely the boost converter uses an inductor rather than a transformer to deliver increased supply voltage.
Can you tell us what switching device you used and the inductance of the coil please? I'd like to try this for myself.

Hi Nuvo,

Yes, it is indeed an inductor. The coil is hand wound around a ferrite using 20 turns in a 1:1 ratio (i.e. a bifilar coil)

The switching (blocking) oscilator is a 2N3904. A germanium transistor would be better but the soilicon one works well enough.

I have not used a diode and capacitor due to space so this lowers the efficiency (and removes protection) and I have drastically reduced the size of the coil but I have increased the number of windings which should help. However of course the smaller coil still means less power.

I plan to make a range of coils that fit the space in the key to see if I can increase the brightness using just these components. I'll post the inductance of those when I have bothered to do the maths.

By removing some of the ribs on the lid of the key, there might be enough room to add a diode and cap to further increase the brightness.

Cheers n

Si

[Fat Audi 80]

That's it Jas, bring the thread down to the level it deserves!

[Jas11n]

Genius Si.
Sadly, I butchered my light giving key many moons ago to make a flip key.
But wanted the illumination again, so I made this.
I can now find the car from 500 yards away in the dead of night









Jase..

[Nuvo]

I really like what you've done there. Surely the boost converter uses an inductor rather than a transformer to deliver increased supply voltage.
Can you tell us what switching device you used and the inductance of the coil please? I'd like to try this for myself.

[HPmuirt]

I am so impressed I would like to post my key to you for the upgradehow much is it?

Err, well the parts only cost about £4 (depending on the quality of the LED) but it takes an hour or 2 to build as hand winding coils is tedious anyway, but when they are that small it is a royal PITA.

Cheers n

Si

[4WheelDrifter]

Nice one Si. I like it.
Amazingly my S2 torch key still works, I just checked. But I wouldn't mind an upgrade.

[HPmuirt]

I'm not daft, I know DC won't go through a transformer...

Err, but this is effectively a simple buck-boost converter (DC-DC converter) - like a really simply version of the type found in every mobile phone or in LED path lights etc

Cheers n

Si

[HPmuirt]

I think I'd have gone the use a lithium coin cell replacement to get the 3 volts or even two 1.5 volt silver cells in series as the easier option

That was my first thought, but I could not find a lithium coin cell the same size as an LR9. Next I was going to use a smaller lithium cell and "pad it out" a bit but I had always fancied doing this as I knew the theory and liked the challenge of making a miniature version.

Cheers n

Si

[Rikki Kitto]

I am so impressed I would like to post my key to you for the upgradehow much is it?

[newsh]

I'm not daft, I know DC won't go through a transformer...