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Phototransistor vs Photodiode

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Ayne said:
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.
 
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...
 
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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.
 
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!
 
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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.
 
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

Code:
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**
 
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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???
 
gramo,

Thanks for the link to the display. Is it a good idea to get one with a backlight?
 
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mbu said:
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.
 
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
 
mbu said:
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...
 
Grab**broken link removed**, its a free version of the real deal, but heres a program made with it that might get you started;

Code:
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 :)
 
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