Discussion in "General help Guidance and Discussion" started by    Mamat    Nov 4, 2010.
Wed Jan 19 2011, 02:44 pm
hi Mamat
u can use pull up resistor to give extra power to led to bright
u can also use led in common anode configuration

now i decide to use 5volt for pic and connect to max3232 and connect to xbee.Can or not?

yes u can also done it
Thu Jan 20 2011, 02:28 am

at89c51 is cmos as c stand for cmos and it operate on 5.5 volt maximum as 74LS xx series and even cd40xx is a cmos and operate at 15 volt maximum
can anyone explain me what these differences are in TTL,CMOS and PC logic levels.


CMOS gave very low current consumption but I'd guess they could not make it work below about 10 volts.

As the technology advanced lower voltages were possible, so we have the low voltage CMOS devices
of today.
Fri Jan 21 2011, 12:56 pm
hi ExperimenterUK
thank u
pc lies in which technology i think also CMOS
TTL has more power consumption as compare to CMOS
Fri Jan 21 2011, 02:01 pm
majoka you are right TTL is more power consumption technology as compared to CMOS...

CMOS has good packing density. TTL takes up more space CMOS has better noise immmunity. TTL has a smaller noise immunity range CMOS has a large fan out. TTL can power less inputs CMOS consume less power. TTL use more power CMOS are highly static sensitive. TTL IC's tend to be less susceptible to static electricity CMOS uses FETS (Field-Effect Transistors) TTL uses BJTs (Bipolar junction Transistors CMOS can run with a range of supply voltages. TTL IC's run with a 5V supply. CMOS uses Vdd and Vss for it's power connections TTL uses BJTs.

TTL More Powerful and Durable

CMOS takes a lot less power and is therefore suitable for battery applications, but generally speaking can't run as fast. TTL devices can drive more power into a load. CMOS chips can be damaged by static electricity: even a static jolt that you or I can't feel might destroy a CMOS chip!

Logic Threshold Voltage Levels

Fri Jan 21 2011, 07:48 pm
lets not deviate from Mamat's topic okay? Mirza you can put this up in a new topic to explain all the logic level details.. its nice to have it on forum. will be very informative.

my pic wide range 2-5volt,when i try output at led very low and not enough power supply.now i decide to use 5volt for pic and connect to max3232 and connect to xbee.Can or not?

LED needs current to glow and usually controller pins are not capable of providing high current needed by LEDs. so you have to go other ways like majoka explained using a pullup or a transistor or using in common anode configuration.

whereas incase of xbee and controller, both need logic levels to communicate and logic levels are actually voltages so current does not come into picture. so in real there is no need of line driver in between them. just make sure both run on same voltage.

[ Edited Fri Jan 21 2011, 07:48 pm ]
Mon Jan 24 2011, 02:33 pm
now i have all device xbee 3.3v pic18f4620 5volt and max3232.can i connect xbee to max3232 to pic?if can plez show me how.
Mon Jan 24 2011, 02:55 pm
see the data sheet of max 3232 is that has 3.3 volt or 5 volt
connect that to 5 or 3.3 volt as what its data sheet says
connect controller to 5 volt
xbee to 3.3 volt
Mon Jan 24 2011, 04:19 pm
if you really want that buy i DON'T UNDERSTAND WHY!!?!?!

connections gonna be like this:
xbee <-> max3232 <-> max3232 <-> pic
Mon Jan 24 2011, 11:34 pm
@ Ajay Bhargav
why we need two max3232
is it any special reason
Thu Jan 27 2011, 08:25 pm
xbee (TTL) <-> max3232 (RS232) <-> (RS232) max3232 (TTL) <-> pic

thats the reason you need 2 max

if you do this
xbee (TTL) <-> max3232 (RS232) <-> pic

BOOM! your controller goes in trash.

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