[MOVED] circuit related questions

[khangzing]

Ok..is that multimeter or enough speed to measure the voltage as u said it is very fast?i will try measure again on Monday and if cant,will try your circuit..

 

[khangzing]

i can't get the wave again....what is the problem....i didnt make any changes,today go and test it show the noisy wave again...zzz...

 

[Venkadesh_M]

check the crystal circuits and vcc and some settings in CRO..

 

[khangzing]

vcc connected,crystal circuit ok(since i didnt make any changes), setting in cro ok...same as that i posted previously...

1 more question, my 38khz should be 9bit resolution?so which number should i load into CCP1CON<5:4> ?? the value i had loaded is 00..

 

[Venkadesh_M]

https://www.micro-examples.com/public/microex-navig/doc/097-pwm-calculator.html

- - - Updated - - -

/*
* PWM registers configuration
* Fosc = 20000000 Hz
* Fpwm = 37878.79 Hz (Requested : 38000 Hz)
* Duty Cycle = 50 %
* Resolution is 9 bits
* Prescaler is 4
* Ensure that your PWM pin is configured as digital output
* see more details on http://www.micro-examples.com/
* this source code is provided 'as is',
* use it at your own risks
*/
PR2 = 0b00100000 ;
T2CON = 0b00000101 ;
CCPR1L = 0b00010000 ;
CCP1CON = 0b00011100 ;

 

[khangzing]

This 1 not so accurate right?

 

[Venkadesh_M]

that is for 37878.79Hz is that no accurate?

 

[khangzing]

if pr2=131, duty cycle=65, it is 381xx, haha~ it is correct...i got no idea why i cant get the same wave............

 

[Venkadesh_M]

Thats why i said first of all try to make a LED blink... after that load your program...

 

[khangzing]

this is the pdf i get from vishay, in page 4,my sensor is that type. and, it need AND gate to operate with the 38 KHz? and the resistor 470 ohm is come after LED?then the voltage will damage the emitter or not?

 

[Venkadesh_M]

You are facing what kind of problem???

 

[khangzing]

No...just asking is that I didn't connect as the PDF mentioned that's why my emitter not working?

 

[Venkadesh_M]

You need not to connect likes that, You can generate any kind of square wave from a Microcontroller....

 

[khangzing]

I mean the emitter side..anode to supply and cathode to 470 resistor..

 

[Venkadesh_M]

at any emitter and receiver your circuit is enough with varying duty cycle.....

 

[khangzing]

What you mean?

 

[Venkadesh_M]

Closely look at the need of that AND gate Its given for modulation purpose that means if you give a logic one it will give a 38khz to emittter, if you give logic zero means 0 in the output you can directly getnerate the modulated signal from microcontroller....

 

[khangzing]

I mean the emitter should I connect the anode to the power supply and cathode to the 470 ohm and the 470 to the collector of npn transistor?

 

[Venkadesh_M]

its nothing using transistor that is just used to drive the led you can just directly connect the led in pic microcontroller pins its able to drive...

 

[jayanth.devarayanadurga]

See this https://www.vishay.com/docs/81010/tsal6200.pdf

The forward current is 100 mA for the IR transmitter. I think you need to make it work at 50 mA or 75 mA for good results. For 5V resistor value will be 100 Ohms. 5V/50 mA = 100 Ohms.