Digital Multimeter (RPM, CNG, Temperature) for ALTO

[uetian04]

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

Total cost should not more RS 1500 max or even lower than this.

[getmoa]

Total cost should not more RS 1500 max or even lower than this.

thank you very much

[theboss]

Great..you should think about putting it into mass production now and turn it into professional business.

[NoWorNeVeR]

WOW. Great work

[uetian04]

WOW. Great work

Thanks

[AdiThenewton]

Salam,

i want to make cng digital meter just for experience this project, now the problem is that i dont know how to get started with.

i saw the cng default switch with lot of wires now the problem is that how do i know which wire doing what, can you tell me how i can make the digital cng meter with microcontroller.

thank you

I have made digital RPM meter, digital CNG meter and temperature meter and battery voltage meter for my Alto. The display can be selected (RPM,CNG,temperature and battery voltage)with push button installed on display.

Regarding accuracy of measurement:

For CNG:
I don't calibrated/verified CNG and RPM measurement yet but i think it should be close to be accurate. For CNG, i used same sensor to measure that used to show CNG on default (4-led point) on conversion switch. 0-200 bar pressure corresponds to 0-100 % on digital display. This reading , 89 % matched with CNG pressure on gauge installed under bonnet when i first installed. I will verify further readings when CNG pressure will be vary in cylinder (75, 50 25 bars).

For RPM:
I used ignition coil pulses to read RPM of engine. As Alto engine is 4 cylinder, so I think it gives 2 pulses/rev from primary of ignition coil . These pulses are directly measured by micro controller in about 0.5 sec time window after interface circuit, that remove noise and spikes. so i think RPM displayed is almost accurate. The RPM interface circuit with ignition coil is given for interested ones.

Important:

In design of RPM meter interface circuit to ignition coil, The points must be considered.

[LIST=1]
[*]The interface circuit must not draw excess current from coil other wise proper spark may not produce in spark plug and as a result engine performance may decrease, more fuel, less millage bla bla. In above circuit max high current is 6 milli ampere so I think this is small and safe. I have tested it and it gives no problem for me.

[*][MORE IMPORTANT]The circuit should be protected from short circuit path to engine body/-ve terminal. As measuring point is taped from ignition coil primary winding, so any permanent short circuit to body will cause unable to start engine. Or it may damage ignition coil as current will continuously flow in coil regardless of distributor timing signal. This is accomplished with 4-redundant resistors in circuit.

[*]The interface circuit should be electrically isolated from rest of circuit to avoid interface noise with micro controller. This is achieved with so called opto-coupler.
[*]This interface should be place/ installed physically apart from micro controller circuit to avoid noise and transient effects. Otherwise noise may disturb FM radio/modulator signal.I installed this circuit under bonnet to achieve this purpose.
[*]Normally ignition coil voltage ranges roughly from 12 V to 14.5V (thanks to Xulifqar, PW senior member). But just after spark finishes, this voltage (at taped point) may reach up to 100V transient (inductive kick). So circuit should be protected from these transient. I used 27 V zener for this.
[/LIST]
Hopes this helps

Note:
The large digit is reserved for gear display. I will add this functionality later in this project (if succeeded).

[nabeel.yamin]

have you done any DIY to read the speed of car?

[uetian04]

Salam,

i want to make cng digital meter just for experience this project, now the problem is that i dont know how to get started with.

i saw the cng default switch with lot of wires now the problem is that how do i know which wire doing what, can you tell me how i can make the digital cng meter with microcontroler.

thank you

Ok, on the back side of CNG conversion switching unit, there are RED, BLACK and WHITE color wire among other wires

RED wire is +12 V switched power, mean it powered on when, ignition key is ON position,
WHITE color wire is CNG presser signal wire that is coming from CNG sensor, installed on CNG kit,
BLACK color is chassis ground or -Ve battery power.

you want to make CNG meter that shows level on some digital display:), It would be easy if u have used some micro controller in ur projects. Cost should not more than 200 RS.

If u want to make, I can guide/help you step by step:)

[uetian04]

have you done any DIY to read the speed of car?

I did not do any DIY for speed measurement yet, but it can be measurement easily at least in ALTO, I know.

[hdaackda]

Can't see the pics but from what I read, amazing job

Sent from my GT-I9300 using Tapatalk 2

[uetian04]

Can't see the pics but from what I read, amazing job

Sent from my GT-I9300 using Tapatalk 2

thanks

[nabeel.yamin]

I did not do any DIY for speed measurement yet, but it can be measurement easily at least in ALTO, I know.

any ideas how you would achieve that? as far as i know, speed signal is mechanical measure by rotation. only thing i can think of is optical sensors but translating it is a problem.

[uetian04]

any ideas how you would achieve that? as far as i know, speed signal is mechanical measure by rotation. only thing i can think of is optical sensors but translating it is a problem.

Yes it is mechanical measure, But today's vehicles are equipped with speed sensor that produce electrical signal (hall sensors?) according shaft rotation.
In Alto, 4 electrical pulses (0V & 12 Volt) are produced per shaft rotation. You know the tyre size of vehicle. Converter that size into tyre diameter > circumference. So know how much tyre cover distance in one rotation.
Read pulses from speed sensor in specific time. Do some math and you will get speed of vehicle.

I can help you if you want to make this DIY.

[nabeel.yamin]

Yes it is mechanical measure, But today's vehicles are equipped with speed sensor that produce electrical signal (hall sensors?) according shaft rotation.
In Alto, 4 electrical pulses (0V & 12 Volt) are produced per shaft rotation. You know the tyre size of vehicle. Converter that size into tyre diameter > circumference. So know how much tyre cover distance in one rotation.
Read pulses from speed sensor in specific time. Do some math and you will get speed of vehicle.

I can help you if you want to make this DIY.

i got the same exact idea after googling but i have reservations that reading those pulses would draw current and impact the speedometer reading. i'll experiment and see what happens. what would be your choice of component for this purpose considering minimal current draw.

[uetian04]

i got the same exact idea after googling but i have reservations that reading those pulses would draw current and impact the speedometer reading. i'll experiment and see what happens. what would be your choice of component for this purpose considering minimal current draw.

You can use high value resistor (10K?) with pulses output, it will draw about 1ma current. I think this is not problem for excess current.
Also opamp (741) for interface if u think over current issue. You can use uC (AT89C51, RS 70) or PIC16F72
, RS ~80) for reading pulses and display. Use 7 segment for display...just GOOGLE https://www.google.com.pk/search?q=7+segment+display&hl=en&client=firefox-a&hs=OFz&sa=G&tbo=u&rls=org.mozilla:en-US:official&channel=fflb&tbm=isch&source=univ&ei=3agKUbXdPJHssgbkkYCoAw&ved=0CDcQsAQ&biw=1280&bih=608&sei=9qgKUYHFLIrhtQa92YGgBw

[nabeel.yamin]

7 segment is no problem although I'm not interested in displaying speed. I want to install eps for which this input is required. But definitely it will be a plus if i can fit some elegant display in meter. I'll need your help when i start this DIY

[uetian04]

7 segment is no problem although I'm not interested in displaying speed. I want to install eps for which this input is required. But definitely it will be a plus if i can fit some elegant display in meter. I'll need your help when i start this DIY

Ok, let it start.
I am here to help you all the way, Where I can!

[mfarhansabir]

Ok, let it start.
I am here to help you all the way, Where I can!

Sorry if I am going off topic. I want to install a digital temperature guage in my cultus carby. And read the temp from engine water out. Not from the manifold where the current temp guage measures temp.

Sent from my Nexus S using Tapatalk 2

[uetian04]

Sorry if I am going off topic. I want to install a digital temperature guage in my cultus carby. And read the temp from engine water out. Not from the manifold where the current temp guage measures temp.

Sent from my Nexus S using Tapatalk 2

Why important to measure water out temperature? I think engine temperature measure is useful.
for this u can put washer type temp sensor on engine bolt. Just remove bolt and put washer type sensor and tighten again. the rest is measurement circuit. This way is very easy. No alteration is required.

Where u want to install the temp display.? I think the 7 seg display is better...

[mfarhansabir]

Why important to measure water out temperature? I think engine temperature measure is useful.
for this u can put washer type temp sensor on engine bolt. Just remove bolt and put washer type sensor and tighten again. the rest is measurement circuit. This way is very easy. No alteration is required.

Where u want to install the temp display.? I think the 7 seg display is better...

Yes thata possible too. But i guess the correct inside engine temp will be depicted by the water coming out.

You are right its much easier though. 7 segment display is fine. I just want to keep an eye on any abnormality in engine temperature (if radiator looses water etc).

Sent from my Nexus S using Tapatalk 2