Post by thread:[PIC]:IR receiving serial data , explanation sough

Hi, I have an IR xmitter sending the string "1234567890abcxyz" over my setup. (F628 - PWM 40khz carrier, RB2 TX 1200 baud). The receiver is a F84 hooked to an LCD with the RX hooked directly to a GP1U26x module. The strange part is I have the two units 3 feet apart on my bench, when xmitting on a straight line of sight, I get about 60% errors in the string. However, when I place my hand directly in front of my two diode emitters, I get 100% accuracy everytime ? Could somebody explain this or possibly a solution ? Thanks, Kevin Xmit Circuit was figure 6 from http://www.rentron.com/Infrared_Communication.htm -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

On Thu, 6 Dec 2001 22:12:44 EST, .....PICLISTKILLspam@spam@MITVMA.MIT.EDU wrote: >Hi, I have an IR xmitter sending the string "1234567890abcxyz" over my >setup. (F628 - PWM 40khz carrier, RB2 TX 1200 baud). >The receiver is a F84 hooked to an LCD with the RX hooked directly to a >GP1U26x module. >The strange part is I have the two units 3 feet apart on my bench, when >xmitting on a straight line of sight, I get about 60% errors in the string. > >However, when I place my hand directly in front of my two diode emitters, >I get 100% accuracy everytime ? Could somebody explain this or possibly >a solution ? >Thanks, >Kevin > Possibly your transmitter is powerful enough that it's swamping the receiver photodiode or amplifier? Putting your hand in front of the emitters blocks/scatters enough of the signal that the receiver gets a reflected or attenuated IR signal and that doesn't swamp the reciver circuit. I've seen this happen before when directing a handheld transmitter directly at a receiver from a foot or so away. Maybe try reducing your transmitter LED current or only use one LED? Matt Pobursky Maximum Performance Systems -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

> Hi, I have an IR xmitter sending the string "1234567890abcxyz" over my > setup. (F628 - PWM 40khz carrier, RB2 TX 1200 baud). > The receiver is a F84 hooked to an LCD with the RX hooked directly to a > GP1U26x module. How do you modulate the data onto the carrier? I don't know the Sharp receiver, but the ones I know are not designed to handle a 'continuous on' signal. They need 'off priods' in the signal, like all IR codes have. Maybe your signal oversteers the receiver? Wouter -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu

Hi Wouter, The circuit is figure 6 on this page www.rentron.com/Infrared_Communication.htm I feed the 40khz carrier and the serial data into a 74HCT132 2 input NAND Schmitt Trigger. {Quote hidden}>> Hi, I have an IR xmitter sending the string "1234567890abcxyz" over my >> setup. (F628 - PWM 40khz carrier, RB2 TX 1200 baud). >> The receiver is a F84 hooked to an LCD with the RX hooked directly to a >> GP1U26x module. > >How do you modulate the data onto the carrier? I don't know the Sharp >receiver, but the ones I know are not designed to handle a 'continuous on' >signal. They need 'off priods' in the signal, like all IR codes have. Maybe >your signal oversteers the receiver? > >Wouter > >-- >http://www.piclist.com hint: To leave the PICList >EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu > > > -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestspam_OUTmitvma.mit.edu