PIC voltage suddenly DROP~!!!!!!!!!

[Gundam82]

YOo... Big problem.... i doing my project.... my PIC is input pin is connected with a receiver module..... both using same supply... problem is

when one buttons is pressed, receiver got the signal(my piC is in off condition) .. once i turn on my pic at the same time.. the signal at receiver immediatly drop to zero volts..... so i cannot get the input from transmittor to activate my PIC.. pls pls

 

[Nigel Goodwin]

YOo... Big problem.... i doing my project.... my PIC is input pin is connected with a receiver module..... both using same supply... problem is

when one buttons is pressed, receiver got the signal(my piC is in off condition) .. once i turn on my pic at the same time.. the signal at receiver immediatly drop to zero volts..... so i cannot get the input from transmittor to activate my PIC.. pls pls

It's not very clear what you mean?, perhaps you had better post the section of the circuit?.

I'm presuming you mean the output of the receiver goes to a PIC I/O pin, and when the PIC is powered up it pulls the receiver output low?. In which case it sounds very much like you have the pin configured as an output, rather than an input.

 

[Gundam82]

sorrry~~ now i dun have the circuit yet.. wat i mean is.... i got one wireless module.... and one PIC... then..the PIC i using is 16F877A.. the input pin i assigned i put 2.2KoHM as pull-up resisitor there..... then...the wireless module(receiver) output is connect to the input pin of the piC that mentiond.....

problem------->
a)when PIC is OFF
i pressed a button from transmiter.. receiver got output... 5V..

B)when PIC is ON
the output receiver that connected to pIC is immediatle drop to zero volt.. once PIC is ON..

Is that possible that there is mismatch impendance occurs????

 

[StupidDum]

Check the input voltage when RF module is on
probably that draw too much current, if battery is used as power supply

 

[kentken]

Which Port are you using?

Please post the setup of the ports, for error checks.

Check the data sheet on the RF, for power req. and decoupling, etc.

Kent

 

[Nigel Goodwin]

Is that possible that there is mismatch impendance occurs????

No - the PIC I/O pins have very high input impedances, and you're using a 2K2 pullup - it's far more likely you inadvertently have the pin set as an output!.

 

[Gundam82]

hey guys......... i think the PIC draws a lot of current.... now i using a transistor 2N2222 as my a switch to let 5 volts from PIC to flow to the input of PIC...... but not 5 volts from receiver...... its work's well..... erm~~~ why ya??
is that any other solution??....................





KEeP LeArnInG~~~~ :twisted:

 

[Nigel Goodwin]

hey guys......... i think the PIC draws a lot of current.... now i using a transistor 2N2222 as my a switch to let 5 volts from PIC to flow to the input of PIC...... but not 5 volts from receiver...... its work's well..... erm~~~ why ya??
is that any other solution??....................

Try posting your complete circuit, PIC input pins are VERY high impedance, and draw almost no current at all - try checking the datasheet for full details.