PIC16F84-based Tachometer

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tacho pic

yes.. SiliconChip april 2000... I already have downloaded the ASM/HEX at their "downloads" section...

done it on breadboard... although I know I still lack some parts configuration, it works.. a bit...

here are the results...

>>>> for the switches, there are 3.. MODE,UP,DOWN.. common connection is at RA4(pin3) tied to +5V with 10k, for MODE(RA0-pin17), for UP(RA2-pin1), and DOWN(RA1-pin18) and I have no IDEA how to set it...

>>>> xtal is 4MHz

>>>> MCLR , 10k to +5V

>>>> for the 7 outputs, RB1(c) RB2(d) RB3(e) RB4(f) RB5(a) RB6(b) RB7(g)... uses common cathode(or anode?) multiplexed 7 seg display.... uses ONLY 2.... the hundredths (RA2-anode)and Thousands (RA1-anode)... the other 2 7-seg is just lighted "00" so as to make the reading direct... refresh rate is fast, about 200mS(i think).. nice... but about the RB1-RB7 designations to the 7-seg display, I think its all mixxed up?? sometimes I get wierd digits...

>>>> regarding the 10 leds, all anodes are tied AND connected to RA0(common for the LED bar) and I think it is connected to a transistor(and op-amp) w/c varies the intensity(of leds) from ambient light..I just ignored it, for simplicity... actually there are only 7 outputs(connected to RB1-RB7) but I dont know where LEd1 would be..etc.... so thats 1-7.. the rest(8,9,10) are all in parallel and connected to RA3(the rev limit)


>>>> signal input is at RB0, tied to gnd with 10k pull-down....

-------------testing----------

with my signal gen, @ 416Hz(About 26,000RPM) the 7 seg (thousands) shows "-" minus.... the article says that if it exceeds 9900 RPM, it will display "-00", and the overREV led lights.... so IT WORKS! prob is I think "some"?? of the connections for the 7-seg are mixxed up?? I dont know... I HAVE no schematic and I just base it from the ASM code....maybe someone could help me out on the 7seg connections??

And THAT is all... not unless someone donates a schema for this....

I really like the refresh rate of this tacho..best I have seen so far... I have tried others but are slow... about 600mS..others 1S...

till then.. just a dream
 

tachometer pic16f

heres the schematic
 

    A

    algor

    Points: 2
    Helpful Answer Positive Rating
16f84 rpm

COOL!! points sent... maybe post also instructions on HOW to set the mode/up/down switches...

check your PM... :-D
 


josepino tachometer

SJ,

So it was in another forum... but still... no article HOW to set it up... for different engines...

I will have a look at that 2nd link....
 

pic tachometer

Hey, i need some help with measuring RPM of a generator. It has a pulse senzor on it. Now i have to build a program to calculate the speed (freq). I've heared something about timer0 on RA4, but i don't know a lot of it, so please....i need some help.
One more thing--->i don't need to disply the rpm, just a sign on output that the rpm reached a certain level of speed (let's say 1010 rpm). in other words...i want an output pin to change from 0 to 1, when the ouput reaches 1010rpm, so the generator starts breaking, and than when it reaches 800rpm, the same pin changes back to 0.
Oh yeah. I'm using MPLAB IDE not C.
tnx guys
 

pic based tachometers

well to be able to program pic16f84a using TIMER0 you need to learn about pic and how to program it , alot of this tutor on the net . thereafter there are hobbyist circuit on the net like this "http://www.josepino.com/' that give you idea how to go about it. although it uses "628A" with little effort you can do this, by changing it configuration and some adjusment. thanks
 

pic16f84 rpm measurement

tnx for your quick reply...i heared today, that it is not possible to make a rpm counter with PIC16f84a, because it has only one counter (tmr0 at ra4), so i can't count pulses and time all at once. So i need a different chip...any ideas which one to choose? i don't need many bits, just a simple 16f84a type of chip, that has two timers.
tnx
 

pic tachometer schematic

Well, you can count the pulses in software and use the timer as the time base.
For your range, if you are getting 1200 RPM, that is 200Hz, or 5ms between pulses (if you are using one pulse per revolution). That is long enough for the PIC to monitor the RPM input and increment a register whenever the input changes from say 0 to 1 (rising edge detected).

Then use TMR0 to generate an interrupt every X ms (say 1sec) and at that point you read the register you have been incrementing and calculate the RPM from that. Then reset the register to get ready for the new measurement.

With a PIC running even at 4MHz you should still be able to achieve what you want. Even with more pulses per revolution.
The loop shold look like this, assuming RA0 is used to count the pulses and Counter is the variable:
Code: 
Wait_0:  btfsc PORTA,0  ;wait for input to go low
        goto Wait_0;

Wait_1:   btfss PORTA,0 ;wait for input to go high (detect rising edge)
        goto Wait_1
        incf Counter,F  ;increment the register
        goto Wait_0  ;go back and wait for the pulse to go back low, etc...

As you can see, the second loop takes only 5 cycles, that is 5us at 4MHz. So this can work with up to 100 pulses per revolution, in theory. In practice, you may need to create a 16-bit counter, which will add a few more cycles, but you get the idea.

This is all the PIC needs to do in real time. When the TMR0 interrupt comes in, the time spent there no longer matters, since you are merely doing calculations, not counting.

Another advantage of the SW counter is that you can do software debouncing, so that if the input pulses are not "clean" you still count them correctly. With a HW counter you get higher speed, but the pulses will need to be very clean, in other words, the signal conditioning has to be much better.
 

tachometer with a pic

topic merged to save some space for same kind of questions

regards
Fragrance
 

16f84a tachometer

bbarney said:
heres the schematic
Click to expand...

can this SC apr2000 be used with 20MHz xtal for a faster "update" of display and still be accurate??


when used with 1-cylinder 4-stroke engine, update time IS VERY VERY SLOW(and is useless) about 1.2second...
 

lm3914 tachometer schematic

hi
sujay from india
did u complete this project
sujay
 

silicon chip tachometer 2000

sujay said:
hi
sujay from india
did u complete this project
sujay
Click to expand...


IF your asking me, then YES I have.... good for multi cylinder engine... TOO SLOW(1.2second display update) for a single cylinder(very impractical)...
 

techometer using pic

OK Here
 

pic digital tachometer


Check ur maill. Coz i send all the project files.
 

pic tachometer project

Hi all,

anyone got an electronic copy(PDF) of Silicon Chip's RPM project??
I believe its the 2000 issue, dont know the month....the one with 7 segment AND 10LED bar display... I got the source code 16F84(ASM) and PCB layout downloaded from the forum somewhere but dont have info on the schematic.. anyone can share??

kindly send to my mail: insafmym@yahoo.com
 

Hello all, I makeing rpm meter whit lcd2x16 and keypad matrix where I should enter my code like 111 and press confirm buton *. Please hellp to do this project for aducation preposition.
 

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