Post by thread:[PIC]: IR Data Link

>What hardware was used? (As there are many devices all with different = >specifications). 16F84 + BC547C + Siemens 3mm infrared LED (20 mA) pulsed at ~80 mA. I don't have a type name, it has a standard 3mm LED body and a blue acryl lens. >What battery life was obtained? 3 * AG10 button cells -> about 2 weeks for 3-5 x use per day (10 seconds rounded up each). The PIC (XT, 4MHz) sleeps most of the time. The cells were to be NiCds (4 x button cells) and rechargeable in the final design. >What sort of transmission speeds were achieved? 2400 Baud with Siemens SFH506-40 (?) IR receiver driving RS232 directly (and powered by RS232 RTS signal). Range ca. 1 meter (1.5 meters with some pointing). PC side things were DOS program and Linux test program. Can use any serial comms package for testing. At 2400 Bauds the SFH is at the limit. 1200 Bauds seem to be better. You will need an error detection and correction protocol (retransmission is ok) and a data filter on the receiver side. The SFH is not quiet when not receiving data. good luck, Peter

> >What hardware was used? (As there are many devices all with > >different = specifications). > > 16F84 + BC547C + Siemens 3mm infrared LED (20 mA) pulsed > at ~80 mA The ZTX transistors (eg ZTX649, ZTX750) can switch more current quicker than the BC range if you need faster baud rates, shorter ON pulses (= longer battery life, you can extend the pulses at the receiver if needed) or extra range. They also work better than the BC's at lower voltages. Put a 100uF cap close to the LEDs to help with instantaneous power demands

Jinx wrote: >The ZTX transistors (eg ZTX649, ZTX750) can switch more current >quicker than the BC range if you need faster baud rates, shorter Actually almost any Japanese small signal transistor blows most European types out of the water. They are also physically smaller to boot and I like the BCE pin config better than the infamous EBC. Also the BC547 is available VERY cheap everywhere... >you can extend the pulses at the >receiver if needed) or extra range. Is there a way to tamper with the (epoxy sealed) innards of the SFH506 I don't know of ? Because the limitation is in the internal Schmitt timing of the SFH506. It is designed for TV/VCR remote service and it won't pass fast pulses without distorting the timing. Did I mention that you need a leader to allow the SFH to train on the received signal ? Peter