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OK, now 298 is working as i want [...]
[...] but should i connect any resistance or buffer to 298 enable and input pins??? while connecting uC to 298 directly will cause any hazard or not??
Why didn't it work before?
But IR led switching at 38Khz........but here it is not used why???
I'm not sure I understand what You as for.
As in fig you can see there is no source of 38khz switching freq. which is required for IR led......
You don't necessarily need frequency modulation (if You have that in mind).
QuoteYou don't necessarily need frequency modulation (if You have that in mind).After checking 3 different IR lED i came to know that IR can work without any switching freq. ( common used 38Khz) i was watching with digital camera all are glowing like visible LED ..But why in remote control we use switching freq. for IR led??
Remote controls switch at 38KHz primarily to make it easier to filter out the noise from background light--the receiver is often pointed towards a window, so being able to pick only the 38KHz signal helps to significantly improve the SNR. This is not nearly as much of an issue for line following, since the main light source is the LED.
Do You ask about IR circuit used for line following or for remote control?
How was competition? Smiley
OK, as my IR circuit was totaly different as in society of Robots so can tell me how to make more sensitive circuits for R sensors.......
R2 and T1 creates voltage divider. If You measure voltage between them when IR LED rays are detected by T1, You get around 0V as T1 is fully ON. When IR LED rays are not detected - T1 is fully OFF, hence voltage between T1 and R2 is going to be around Vcc.
What do You mean by "more powerfull"? What do You want to achieve with comparator? What do You want to achieve with modulation?
There can be with some CMOS digital inputs because if the voltage is between logic states, both transistors in a totem pole will be conducting, and it could get hot.