Some kind of RPM counter

[Untitled_user]

Well,
on this schematic from datasheet, I actualy wanted to ask if magnetic principe could be somehow changed with optical... i forgoted  I belive that magnetic could not be used, beacuse it's about electric motor, so it will disturb the work of counter...

And on this design with 555 I should add a freq/voltage converter to drive a analog meter, isn't it?

So, i dont know what to do... the both solutions seems to be quite good, simple and cheap... And I ask you, masters of electronics: what to do? I'm gonnig in electronis school, we courently learning basics about analog and digital electronics u know: transistor amplifiers, multivibrators, digital logic, TTL, CMOS, voltage ragulators...so I belive that I soon wont bother you with such simple projects, and I could design some circuits at my own...  ;D
And by then, I would appreciate a little help...

Marc

 

[Untitled_user]

Hi,
I was thinking a bit about that counter...
I redraw those schematics and now I'm posting them; one with LM2917, and other with 555 timer.
I do not know if this one with LM will work, but it looks damn simple  ;D
And if I use the 555 circuit, I will anyway have to use freq. to voltage converter at output, am I right?
I think that would be time to pick up way to go, so, what do you sugest, and why?

View attachment 38391

View attachment 38392

 

[audioguru2]

Sorry, but your LM2917 circuit won't work:

1) The LM2917 has a 7V zener diode at its supply pin that will blow-up when you apply 15V to it.
2) The 8-pins versions have a differential amp at their inputs with one input grounded and have hysteresis, so their input voltage must swing above and below ground to work.

The 14-pins LM2907 does not have the zener diode, and has truly-differential inputs so that one can be biased at a positive voltage then the other input can have a pullup resistor for the photo-transistor (your circuit doesn't have a pullup resistor for its photo-transistor).

The datasheet explains everything about them:

View attachment 38397

View attachment 38398

 

[Untitled_user]

After long time, hello again...

I'm back to bother you...
Audioguru:
I would ask you something: Would you, please, be so good to quickly sketch a schematic for me? I see that if we (better said I  :-[) continue so, we would come nowhere...  I belive that would not be too big problem for master like you... Please?
And if answer is yes, i would like Vcc something like 5 or 9V...

Marc

 

[audioguru2]

Hi Marc,
I have added a coupling capacitor from the phototransistor and a resistor to ground at the tach's input.
The LM2917 won't operate from 5V so I have planned a 150 ohm resistor to feed its zener diode from 9V (not a 9V battery, its voltage drops too low) and some supply bypass caps.

View attachment 38554

 

[Untitled_user]

Hi,
This was realy quick and professional... Very nice 
THANKS!!!

Of course, have a question again:
Can you, please, write down some diodes and transistor pairs that can be used..?
I looked online catalog here by us and it's a bit confusing...
And, I supose that now I can directly drive analog meter form output, isn't it?

Marc

 

[audioguru2]

Hi,
This was realy quick and professional... Very nice

 

[Untitled_user]

Hi,
well, i really don't know wich ones to take... never had experience with photo elements before... but, its time to change it...
I atached a list of elements from our 'local' shop... don't worry, it's only about 30 of them...  ;D And I'm soory if the choice is bad... we don't have much electronic stores, and what we have is ussualy expensive... Hope it's gonna change some day...
So, please find something for me...

Have a nice day...   

opto.txt

 

[Untitled_user]

Audioguru?

 

[audioguru2]

Hi Marc,
Many of the opto items on your list are "Optical Isolators" which have its LED shining internally on a photo-diode or photo-transistor and therefore can't be used as a tachometer.
Go through your list and sort them at www.datasheetarchive.com .

 

[Untitled_user]

Hello,
sorry about theese opto isolators...
Here is the filtered list...

opto.txt

 

[audioguru2]

The BP103 photo-transistors have a very wide 55 degrees pickup pattern. Any of the other photo-transitors on your list have a much narrower pattern and would be fine.

I am sorry but I didn't look at all the photo-diodes. Some might be an optical emitter , others only infrared which you can't see and others might be a detector instead of an emitter.

 

[Untitled_user]

OK, and thanks a lot!
I will buy parts as soon as i get and assembly this circuit...
Till then...

Cheers!

 

[Untitled_user]

Hi!

I'm back again. I assembled the counter... 
Tooked BPW40 and ordinary white LED.

And of course, there are the problems...
1. It works just fine when I put the diode on one side of rotating disc and transistor
    on the other, and cut a hole in disc so Tr can 'see' diode in one moment of
    rotation. (excuse me for bad description, hard to me say it in English  :'()...
    But when I try to put them both on the same side and use reflection from
    white/black area, it doesn't react. What can I do?
2. OK, this one I belive can be done later, but anyway: how to calibrate the   
    meter?

Regards

 

[audioguru2]

Your white LED is really a blue one with a yellowish phosphor, and doesn't match your phototransistor's color response very well. It can be made much more sensitive:

1) The phototransistor can be made more sensitive by increasing the value of R4. The resistor at pin 2 should also be increased so that its value is up to 10 times higher.

2) The LED can be made brighter by decreasing the value of R3 to 220 ohms for the white LED that probably has a forward voltage of 3.3V to 3.6V and a 9V supply.