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03-02-2005, 06:11 PM
Hi;

We are making this line follower

http://www.kmitl.ac.th/~kswichit/LFrobot/LFrobot.htm
and we used the exact same components for the linfollower I have already lost two microcontrollers (at89c2051) .Can you tell me the values of the resistances and the other things to be connected
between
1)sensors--mcu
2)l293d--mcu
3)pins 10,18 of mcu----- ground

what are th rules to be followed while interfacing the mcus so that they dont blow up..

vidur
03-02-2005, 07:49 PM
I saw the circuit diagram.....

The probable cause for such anomalous behaviour is excessive generation of transients

Some suggestions

The start button is directly toggled to GND...not a good thing to couple data lines to a power supply...try putting a 220 ohm resistance before the pushbutton

Another thing....Youre' using LEDs with the 470 ohm pull up resistors in the sensor-mcu interface....

LEDs have too much capacitance....a 470 ohm pullup resistor may give it a sufficiently small time constant to cause a sharp transient...& zap the mcu

Suggestion....remove the LED. & put it somewhere else( not anywhere near the MCU)...or use a higher value Pull up resistor.say 1K ( but this may cause LED brightness problems...& hence i suggest you do away with the LEDs.....


To be double safe....use hex buffers to isolate the MCU from the sensor interface...

I dont think you need a interface between the MCU & L293d.....since it was supposed to be an interface b/w a controller an a motor...& hence the designers would have taken sufficient precautions


Vidur

mishradk
07-06-2005, 03:09 PM
Hi
i was just reading the post...
but what is the Hex buffer you are talking about?
"To be double safe....use hex buffers to isolate the MCU from the sensor interface... "

Could you please tell me out this?

Regards
DK

ice
07-07-2005, 10:30 AM
A "buffer" literally means to "absorb" as in absorb to reduce damage

A buffer in a electronic circuitry means to protect devices,maybe from an overvolage or a spike..if nethin "bad " happens..the buffer blows out first protecting the device..in this case the micro

A HEX buffer has 6 buffers,normally NOT gates.

You can even use optoisolators for such stuff..tht is primarily used as a buffer