Digital multimeter for your car

Digital Speedometer, Tachometer & Engine temperature display.
4 months before, I treid to build a digital tachometer & speedometer using seven segment display, but I failed to do it the right way. The circuits I used before were too crowded with ICs & other components. Then I managed to build the LED tachomter. Later, I got a stepper motor & used it as a speed sensor to build the LED speedometer successfully, too.
I was always thinking of the Seven segment multimeter. I know it's simple to build such circuits using PICs about which I know nothing :)
The ICL7107 came to my mind. A simple, old yet reliable analog to digital converter used in digital voltmeter circuits. VOLTMETER? Why not to build a voltmeter, then calibrating it to get the car speed from my stepper motor? & get the RPM from my LM2917 voltage output? What about adding a digital thermometer using the LM35 temperature sensor?

Step 1 Video

Comments

[kill_them_now]

nice work..what should if i want to modify this circuit using lcd interface instead of
led?

[fernandohdz]

Hi Again From Merida Mexico
After a lot of searching on the web i found that you are the best answer
Question: This i a Pic system? Im very new on this and i dont know if the icl7101 IC have to be programed??? and how to do it...
If so the signal of ech sensor (lm35, step motor and lm2917) is "translated" to the leds and 7 segments display?
Thanks and sorry for the rocky questions
FH

[abo_hosni]

this is not PIC system :)
ICL7107 is analog to digital converter and not to be programmed

[fernandohdz]

Hi
I have an old motorcycle that im rebuiling and dont have all the clocks this is exactly what i need but im not to god in electronics, any wat i´m going to try
hope you can reach me and give me a help at [e-mail]
thanks FH

[bega]

hi man, sorry my question but what does it mean dp in the bridge of 21 and 30 pins of the ci that goes to a resist. of 220 and later to the DP but wich pin of the DP goes it or what does it means? i appreciate your soon answer.

[abo_hosni]

DP= decimal point in the seven segment display
if you want a DP to be lit, connect it through 220R. I connected mine to the first (right) DP. It's not necessary at all

[bega]

thanks a lot man and sorry for questions soo sillies, i really want to make it but here in mexico its a little difficult to find the ci, thanks again.

[aussa]

Its nice to see cool projects like this from Egypt!! Try to upgrade to LCD interface and microcontrollers.

[opipharma]

Dear sir
i think u are in egypt
i'd like to ask you about the LM35 where did you buy it and for how much??
thanks

[abo_hosni]

I bought the LM35 from "El Nekhely" in "Bab El louk" :)
It's for 8 L.E.

[opipharma]

thanks alot
as i need to build this thermometer for my suzuki swift but i can't find it at all any where in el gharbiya gov
i was wondering if there's any substitute for it??

[abo_hosni]

Some circuits use regular diodes or transistors as temperature sensors, but you can't make a direct substition in this circuit. Look for another circuit, instead

[opipharma]

Thanks so much

[MOMJE9]

this car, it´s a Renault?

[abo_hosni]

It's Peugeot 504 :)

[mafinstructables]

Hello, why you made changes in the filter of coil signal, respect the led-tacho proyect ??. which one is better ??

[abo_hosni]

what changes do you mean, please?

I prefer the 7 Segment speedo with the LED tacho.

In fact, I don't like LED speedo & the 7 segment tacho too much.

[mafinstructables]

hi, compare this proyect (Digital multimeter for your car) circuit diagram with the DIY LED Tachomter (RPM gauge) diagram. The filter of the input signal of the LM2917 from the coil (negative) are diferent....Nice proyects.
Regards from URUGUAY

[abo_hosni]

Sorry for this mistake. I edited the "parts list" & the schematic.
The capacitor I used as a filter for LM2917 signal is 470nF.
In fact I don't have a reason for this change, but it works :)

Another funny thing about the 100pF cap of Pin No38 of ICL7107. I forgot to buy one!!! I didn't accept to delay the project. So, I connected 10x 1nF caps.(code 102) in series = 100pF lol
This capacitor together with connections to pin 39 & 40 determine the clock speed of ICL7107

[mafinstructables]

Nice resources for capacitors......je... If you check out to the first proyect, you take off the 100nf in parallel to ground also, between 10k resistor and 12v zener....sorry for my insistence..lol
If the second filter for signal for lm2917 works fine in field.... the first can be modified.. less components and more cheap... je..
Regards from Uruguay

[dared]

C O O L

[VadimS]

I love the look. I'd probably use a vfd, I kind of have a thing for them, but otherwise great.

Oh in step 5, image 5 you have a text box inside of a text box.

[abo_hosni]

are there VFD available of suitable size to such project? If so, what about the circuit used.

I edited the text box by the way :) Thanks

[VadimS]

Hmm I actually couldn't find any 3 or 4 digit displays.
Digi-Key has a nice 6 digit unit:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=D0106LT-43-0601-ND

Or you can get single digit tubes off of eBay (sometimes called nixie tubes but there is a difference).

The single digit tube can usually be run right off 12v.

The 6-digit unit I linked to has 3 digits ganged together.
So you would power grid one (34v) power the segments to display the first number then cut power to that grid and power the second grid etc.
If run fast enough it will look continues.
If testing on a workbench by hand 12v should.
The filament needs to bee powered by 4.4v a lm317 should do the trick.

A micocontroller or dedicated driver ic would be needed.

[VadimS]

You could probably just use a 3 ohm resistor from that 5v regulator for the
filament.
That would get you to 4.4v (200ma).

[rimar2000]

WOW, you have done an awesome work!

Congratulations.