Digital Multimeter (RPM, CNG, Temperature) for ALTO

[CutePoison]

Awesome!
Can you tell me about the RPM meter? How did you make it work.?
Also if you can guide me how to make this. I have programmed ATmega 16 (AVR) . Apart from that I dont have much microcontroller experience

[uetian04]

Awesome!
Can you tell me about the RPM meter? How did you make it work.?
Also if you can guide me how to make this. I have programmed ATmega 16 (AVR) . Apart from that I dont have much microcontroller experience

Since you have worked/programmed, you might know about uC timers/counters. RPM measurement is made with counter/timers of uC and interface circuit with ignition coil. 1 timer is used as counter to count the ignition pulses and other is used as time base (0.6291456 sec, for my code) for counter. In this period ignition pulses are counted.
Then RPM is then:
RPM= (counter pules*60)/0.6291456 sec .

By assuming 4-cyclinder of ALTO, counter input is pre-scaled 1:4, i.e counter is incremented after every 4 pulses from ignition coil.

Rest is the way to display RPM on display. You can uses 7-seg or LCD or even TFT as display.

[mkkd]

Gr8 project. Bro try it with matrix LCD display..

[uetian04]

Gr8 project. Bro try it with matrix LCD display..

Initially I planed to used LCD display for this multimeter. Prototype was also built and tested on LCD. More info about initial plan is athttps://www.pakwheels.com/forums/d-i-y-projects/182805-digital-dashboard-my-suzuki-alto. The idea of using LCD is good because it can show all cariable on display at same time. But I could not get manage to installed LCD in Car due to limited space at installation place. So finally used 7-seg LED display.

If some one has idea where and how to installed this LCD, then share with me.

[CutePoison]

Since you have worked/programmed, you might know about uC timers/counters. RPM measurement is made with counter/timers of uC and interface circuit with ignition coil. 1 timer is used as counter to count the ignition pulses and other is used as time base (0.6291456 sec, for my code) for counter. In this period ignition pulses are counted.
Then RPM is then:
RPM= (counter pules*60)/0.6291456 sec .

By assuming 4-cyclinder of ALTO, counter input is pre-scaled 1:4, i.e counter is incremented after every 4 pulses from ignition coil.

Rest is the way to display RPM on display. You can uses 7-seg or LCD or even TFT as display.

How does the counter count the pulses?
how do you connect the counter with the ignition coil?

[uetian04]

How does the counter count the pulses?
how do you connect the counter with the ignition coil?

The counter mode is configured inside micro controller.
The interface circuit for connection to ignition coil is given at top of post.

[uetian04]

@uetian04

yes, plz do share details, i would like to do it too

what details about this DIY, u want?

[cracked]

share all the detail please.. i have a friend who can do this but please share all the details so i can just show your work and ask him to make one for me..
nice effort..but i wana know that alto is 4 cylinder right,so how you programmed the rpm meter to show results in accordance,what if we have 3 cylinder car ? like cultus for instance!

[uetian04]

share all the detail please.. i have a friend who can do this but please share all the details so i can just show your work and ask him to make one for me..
nice effort..but i wana know that alto is 4 cylinder right,so how you programmed the rpm meter to show results in accordance,what if we have 3 cylinder car ? like cultus for instance!

Thanks;
Here is what i diD;

The RPM meter programming is bit simple. First configure microcontroller timer as counter to count the ignition coil (primary winding) pulses in specific time window (say, for 0.5 seconds). Divide these pulses with 4 (no of cylinder, since for 4 ignition coil pulses, 1 RPM completes).

Lets do trick.
Suppose u received N (no of pulses in 0.5 sec) in micro controller timer/counter.
Then simple math:

RPS=(N/4)x2; Rev per second, since we counted pulses for 0.5 sec
RPM= RPSx60 ; for Alto

RPM =((N/3)x2x60 ; for Cultus, if it is 3 cylinder as u mentioned. Btw I don't know:S.

The more important is interface circuit with ignition coil that i have shown in start of post.

[getmoa]

could you do us a favour????

1. would be pleased to know if you could let us know RPM = 3000 in each gear!!

2. any idea about perfect shift of alto in terms of speed in each gear???

both would be different...
kindly assist

[uetian04]

could you do us a favour????

1. would be pleased to know if you could let us know RPM = 3000 in each gear!!

2. any idea about perfect shift of alto in terms of speed in each gear???

both would be different...
kindly assist

Gear 1: RPM:about 3000; Speed 30 Km/h
Gear 2: RPM:about 3000; Speed 55-60 Km/h
Gear 3: RPM:about 3000; Speed 80 Km/h

[getmoa]

Gear 1: RPM:about 3000; Speed 30 Km/h
Gear 2: RPM:about 3000; Speed 55-60 Km/h
Gear 3: RPM:about 3000; Speed 80 Km/h

Oh Dear.... there's something wrong with your device in giving you calculation.... can't agree with those figures for RPM @ 3000.

Well.... thanks & appreciated for giving my post feedback.

[aantherax]

Good (Y) very impressive .... change its look a bit and try selling it professionally

[uetian04]

Oh Dear.... there's something wrong with your device in giving you calculation.... can't agree with those figures for RPM @ 3000.

Well.... thanks & appreciated for giving my post feedback.

thanks

What u think it should be? Btw I will recheck

[getmoa]

thanks

What u think it should be? Btw I will recheck

well as of my experience it would be more than of half the dial figures (x1000).... for sure

as mostly been and am experienced to the RPM length of 8 Or 6 in case of diesels where as of ALTO think the RPM meter is to be of 10....thus at 30 km/hr it should / would cross 7.5 RPM same for being at other speeds

i hope you understood what i tried to express in here..... if not please specify.

someone from others having after market RPM can assist us.

[uetian04]

well as of my experience it would be more than of half the dial figures (x1000).... for sure

as mostly been and am experienced to the RPM length of 8 Or 6 in case of diesels where as of ALTO think the RPM meter is to be of 10....thus at 30 km/hr it should / would cross 7.5 RPM same for being at other speeds

i hope you understood what i tried to express in here..... if not please specify.

someone from others having after market RPM can assist us.

Okay, lets do trick to see if it works:S!

Alto stock tyre size: 145/80/R12 (I have with my Alto), this gives as

Rolling Radius= 10.566 inches
Circumference=66.394 inches
Diameter = 21.1338 inches:
Source:Tyre Size Calculator @ ExplorOz Articles

From pakzsuzuki website Alto, Gear ratio for Alto is:

1st: 3.416
2nd: 1.894
3rd: 1.280
4th: 0.914
5th: 0.757
Rev: 3.583
Final:4.388 (Differential gear ????)

Now KM/h= (0.0095755968*RPM*R)/(GD*GT)
Here: RPM= Rev per Min (for engine)
R= Tyre rolling radius in Inches
GD =differential gear ratio
GT = transmission gear ratio
Source: Speed versus RPM calculator

Assuming no wear and tear of tyre;

If RPM =3000 then
Gear Speed (KM/h)
1st -- 20
2nd -- 36
3rd -- 54
4th -- 70
5th -- 91

Side Note:
For my DIY RPM vs speed checking, i observed reading while I was accelerating the paddle. Not stable RPM on display! RPM reading is updated every 0.5 sec in this project. So If I would note speed while RPM reading is stable at 3000 RPM, then result might be more accurate.

As you said for 30km/h in 1st gear should be about 7500 RPM, this gives 50km/h. Is is OK?

Hopes this helps us to understand.

Waiting valuable comments from @Xulfiqar(H)

[getmoa]

Okay, lets do trick to see if it works:S!

Alto stock tyre size: 145/80/R12 (I have with my Alto), this gives as

Rolling Radius= 10.566 inches
Circumference=66.394 inches
Diameter = 21.1338 inches:
Source:Tyre Size Calculator @ ExplorOz Articles

From pakzsuzuki website Alto, Gear ratio for Alto is:

1st: 3.416
2nd: 1.894
3rd: 1.280
4th: 0.914
5th: 0.757
Rev: 3.583
Final:4.388 (Differential gear ????)

Now KM/h= (0.0095755968*RPM*R)/(GD*GT)
Here: RPM= Rev per Min (for engine)
R= Tyre rolling radius in Inches
GD =differential gear ratio
GT = transmission gear ratio
Source: Speed versus RPM calculator

Assuming no wear and tear of tyre;

If RPM =3000 then
Gear Speed (KM/h)
1st >> 20
2nd >> 36
3rd >> 54
4th >> 70
5th >> 91

As you said for 30km/h in 1st gear should be about 7500 RPM, this gives 50km/h. Is is OK?

Hopes this helps us to understand.

Waiting valuable comments from @Xulfiqar(H)

now that appears to be somewhere near more accuracy/ perfect readings @ RPM = 3000

Gear Speed (KM/h)
1st >> 20
2nd >> 36
3rd >> 54
4th >> 70
5th >> 91

where as my readings were just a wild guess.

Overhere i have another concern, As of my knowledge the gear ratios of almost all cars are near to each other. So is it the only tyre size that effects the calculation in findings of RPM over speed.
Then where does the HP/CC play role to determine the RPM at any given speen.

[uetian04]

now that appears to be somewhere near more accuracy/ perfect readings @ RPM = 3000

Gear Speed (KM/h)
1st >> 20
2nd >> 36
3rd >> 54
4th >> 70
5th >> 91

where as my readings were just a wild guess.

Overhere i have another concern, As of my knowledge the gear ratios of almost all cars are near to each other. So is it the only tyre size that effects the calculation in findings of RPM over speed.
Then where does the HP/CC play role to determine the RPM at any given speen.

I think not exactly same gear ratio among almost cars. More over some cars may having 6 fwd gears (not sure if exists?)so it gives more speed in top gear with same RPM. Even little difference of gear ratio among different cars give considerable change in result for same RPM.
Like 2010 (2010 MY) Honda City Automatic (5 A/T)2010 Honda City Automatic technical specifications with 175/65 R 15 tyre, top transmission gear ratio is 0.55 and final gear is 4.29. It gives 137 KM/h at 3000 RPM in top gear.

I consider higher CC/HP relates to more power/torque than speed.
Or higher CC/HP engines may even run safely on higher RPM, if driven on higher RPM to get max speed.

Or I am getting mis-understanding between final gear and differential gear ratio to be same or some thing wrong with formula?

Experts may give more informative comments, please.

[bravo122]

can u tell how much will it cost me if i make one

[getmoa]

can u tell how much will it cost me if i make one

that was my very first post which was never replied!!!