Phototransistor vs Photodiode

[ikalogic]

When light strike on Photodiode it's resistance increase or decrease??

When light strike on an LDR, it's resistance decrease.

but wen light strike on Photodiode it conducts in reverse bias.

 

[mbu]

Ikalogic,

Since I'm new to microcontrollers I just don't know the power of them. What I should have asked was: Can a PIC16F628A run a LCD display AND keep track of the input pulses and calculations needed for a tachometer? Or... do I need a microcontroller for the LCD and one for the Tachometer?

Thanks...

 

[mneary]

What kind of LCD? Does it have a built in controller? (most do). If it has an 11-pin interface, the controller is built in.

If the LCD has its own controller, then a single microcontroller can to what you need and plenty more.

 

[mbu]

mneary,

Okay... that sounds good! Thanks!

Do you or anyone else for the matter, have a suggestion for a good 16 X 2 LCD display? This would be for indoor use... so what type of back light etc.

Thanks...


Oh, one other thing...

If I use an LED (four digit) would it also be good to use a single microcontroller to handle that and use another microcontroller to do the calculations and counting of pulses for the tachometer? This is for my use only so a couple of dollars either way doesn't matter, I just want a fast and accurate tach!

 

[mneary]

You left no clue as to your location. This is important when discussing sources.

I Southern California I might try eio. Maybe that's because they are only a few miles down the street.

 

[gramo]

US$6.90 @ https://www.futurlec.com/LCDDisp.shtml

Interfacing with them is easy;

**broken link removed**
Note that the PIC's osc and power supply are not shown

Device = 16F877
XTAL = 4

LCD_DTPIN = PORTB.4
LCD_RSPIN = PORTB.2
LCD_ENPIN = PORTB.3
LCD_INTERFACE = 4
LCD_LINES = 2
LCD_TYPE = 0

Delayms 150
Cls

Main:

    Print At 1,1, "Hello World"

    While 1=1                                ' Loop for ever

    Wend

**broken link removed**

 

[Ayne]

Now the simple..
Question is.

+Vcc---/\/\/\/----Photodiode in reverse Bias----GND.

If i make circuit some thing like this, Positive supply connected to a resistor, resistor's second end connected to a photo diode(in reverse Bias) and photodiode's second end connected to GND.

When light strike on Photo diode, voltage drop accross Photodiode will increase?? or decrease???

 

[mbu]

gramo,

Thanks for the link to the display. Is it a good idea to get one with a backlight?

 

[gramo]

gramo,

Thanks for the link to the display. Is it a good idea to get one with a backlight?

Sure, why not. Its an extra PIN, and the little datasheet that comes with it will explain how to wire it up

 

[ikalogic]

Ikalogic,

Since I'm new to microcontrollers I just don't know the power of them. What I should have asked was: Can a PIC16F627A run a LCD display AND keep track of the input pulses and calculations needed for a tachometer? Or... do I need a microcontroller for the LCD and one for the Tachometer?

Thanks...

One uController can do both, there is a tachometer project on my website, with an LCD display. it also shows how to build the sensor.

 

[mbu]

ikalogic,

Yes, I'm planning on building yours... just need to use a MicroChip controller!

By the way, do you have a parts list for it?

Also, you have a pretty neat site - very interesting and informative!

Thanks

 

[ikalogic]

ikalogic,

Yes, I'm planning on building yours... just need to use a MicroChip controller!

By the way, do you have a parts list for it?

Also, you have a pretty neat site - very interesting and informative!

Thanks

you can download schematics+partlist+pcb at the end...

as for using a uchip... i left PICs long time ago.. i've been more than 3 years i never used one... Gramo and Niegel can help you a lot with them.. but the principle of operation os a tachometer of this time is fairly the same...

 

[gramo]

Grab**broken link removed**, its a free version of the real deal, but heres a program made with it that might get you started;

Device = 16F877
Xtal = 20

Dim Result as DWord

LCD_DTPIN = PORTB.4			' Setup the LCD
LCD_RSPIN = PORTB.2			'
LCD_ENPIN = PORTB.3			'
LCD_INTERFACE = 4			'
LCD_LINES = 2 				'
LCD_TYPE = 0				'

All_Digital = True			' Make all pins Digital I/O's

While 1 = 1

	  Result = COUNTER PORTA.0, 100    		' Count how many pulses in 100mS
	  
	  Result = Result * 10 * 60			' Scale To RPM	
	  
	  Print at 1, 1, "RPM = ", DEC8 Result		' Display on the LCD

Wend		   	  	 	  	   	' Loop for ever

**broken link removed**
Click here to watch this circuit and program in action!


Hope that helps

 

[Ayne]

https://www.electro-tech-online.com/threads/rpm-counter-project-started-pic16f877a.28713/
Thread Started by me.
May this help u.