kabilan Posted October 24, 2005 Report Share Posted October 24, 2005 Hi guys,I'm in an attempt to make a school project which will enable audio transmission over a laser medium 5mW/650nm. Here is the link where I got the idea http://captain.haddock.8m.com/laser/laser1.html . Does anyone ever tried building this circuit, was it working?I surveyed electronics shops for available materials for the construction. I found that I have to replace 2n5484 with 2n3819, and bc549 with pn2222 since it was not available. Is this just okay?I have a question with regard to the section where there is a 68 ohms NTC thermistor, the problem is there is no available 68 ohms but there is a 10 ohms NTC thermistor. What should I do with it? Is it okay if I removed the 68 ohms from the circuit or replaced it instead with the 10 ohms?Any ideas is greatly appreciated.regards,Kabilan Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 24, 2005 Report Share Posted October 24, 2005 You can't use 10 ohms to replace a 68 ohm resistor, you risk burning-out the laser diode.Since you can't use the proper NTC, the laser might drop-out when the ambient is cool and burn-out if hot.The photo-diode is backwards in the receiver's schematic, the pcb layout of it is correct. Quote Link to comment Share on other sites More sharing options...
kabilan Posted October 25, 2005 Author Report Share Posted October 25, 2005 hi guru,Thank you for the idea, I appreciate it. :DSince you can't use the proper NTC, the laser might drop-out when the ambient is cool and burn-out if hot.Is there any alternative I can do about it? What can I replace with that section?The photo-diode is backwards in the receiver's schematic, the pcb layout of it is correct.I see.... does that mean the photodiodes do have polarities? How should I be able to identify which terminal should I connect with it? (I should do some more research with photodiodes ;D) Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 25, 2005 Report Share Posted October 25, 2005 Is there any alternative I can do about it? What can I replace with that section?Try it with your 10 ohms NTC in series with a 56 ohm resistor, and don't let the ambient temp change very much.does that mean the photodiodes do have polarities? How should I be able to identify which terminal should I connect with it?Of course, all diodes have polarities. Look at its pic in its datasheet. Quote Link to comment Share on other sites More sharing options...
kabilan Posted October 26, 2005 Author Report Share Posted October 26, 2005 hi guru,Thats great news, now I have some hopes ;). I will start constructing it and try your suggestion. I will let you know how it would go.Thank you very much, you ROCK!!! You are very cool 8) Quote Link to comment Share on other sites More sharing options...
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