Pier Erik m'a gentiment répondu, je vous fais un copier/coller de sa réponse:
About the Annunicators:
It’s quite tricky and I still have some trouble with the sensitivity. It is depended on type
of LCD monitor. For fun I tried an old fashion CRT monitor and no problem at all. The
Annunicator fired at 10cm distance hehehe..
In the current construction I use PT202C
http://www.everlight.com.ua/pdf/ir-transist/PT202C.pdfbut looking for an alternative. LTP 80 looks to be quite nice – very low dark current.
As far as I remember the photo current was about 50uA when the LCD monitor
(annunicator graphics) was light up and went down to ~20uA when off / black
(Background light/emission from the LCD).
So it’s a very small area to trigger on – just a few uA’s. And that is the current
you need to boost up and tune to match.
Let’s say you want 10mA through the LEDs 10mA / 50uA = hFE = 200.
BC547 seems to be able to do the job but in the very low Ib area the transistor
can behave strange.
I tried many different setups and I ended up using two transistors as the best alternative.
Upper left image is the one I use now. A darlington setup up (PTC and Q1) to get max boost
– then feed the LED driver (second 2N2222). Then tune R1 / R2 to current limit Q1 Ic and feed
Q2 with a suitable Ib.
The triple darlington to the right should work as well but it’s quite risky. Easy to blow Q2.
Anyway – my hope was that Level-D could deliver all the necessary Indicators in the SDK.
Let’s hope 757 will do and then I will use the “signals” from the SDK – I think J
and change my MIP pcb.
We don’t know if this will ever happen though and until then I go with
this solution. Nice thing is that we reduce the number of connections & programming and
LCD area is there in any case – so why not use it to something smart / usable J
![Image](http://img15.hostingpics.net/thumbs/mini_598683untitled.jpg)
Je vais essayer de récuperer ces fameux Tz 2222A et tester tout ça
![content rigolus](./images/smilies/icon_smile.gif)