DIY LED Tachomter RPM Gauge

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DIY LED Tachomter (RPM gauge) by abo_hosni on August 28, 2010

Table of Contents

DIY LED Tachomter (RPM gauge) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Intro:  DIY LED Tachomter (RPM gauge) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Step 1:  Building the circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Step 2:  Testing The Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Step 3:  Mounting to the instrument cluster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Step 4:  Final assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Related Instructables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

http://www.instructables.com/id/DIY-LED-Tachomter-RPM-gauge/ 

Intro: DIY LED Tachomter (RPM gauge) This is my LED project. An LED tachometer for my 1977 PEUGEOT 504.

Image Notes 1. yellow windows cut 2. where I put my project

http://www.instructables.com/id/DIY-LED-Tachomter-RPM-gauge/ 

Step 1:Building the circuit This is the circuit I used in my project. A simple one which costs me about 35 Egyptian Pounds for components ( ground 4,8 ----> 6,7 of the 2nd LM3914 6,7 -----> 4.4Kohm resistor (I used 2x 2.2 in series) ---->ground 3,9 -----> 9 Volts (with 3,9 of other LM3914s) 5 -----> signal (with 5 of other LM3914s)

jjmaia says:

Nov 6, 2010. 4:51 PM REPLY

Thanks for your help, but i've got another question. How about the LED voltage? Will it be safe? i want to use green, yellow and Red LED's. One more question, the "1 x 220 Kohm Trimpot variable resistor (for calibration)", is this it? http://cgi.ebay.com/6-pcs-220k-ohm-Trimmer-Pot-top-adjust-4B7-/360295889369?pt=LH_DefaultDomain_0&hash=item53e34ef9d9 And how do i connect it, only 2 or 3 connections? Thank you.

abo_hosni says:

Nov 6, 2010. 6:27 PM REPLY

LM3914 adjust LED current automatically, don't worry. Yes, this is the 220K potentiometer, use 2 connections only (the ri ht one + one of the left ones in picture)

jjmaia says:

Nov 7, 2010. 4:59 AM REPLY

Thank you for your help.

mellink says:

Oct 27, 2010. 9:13 AM REPLY Hi, can i get the electrical plan in a higher quality im trying to read it and struggling. Really want to do this mod! What is the XXX7809? Thanks :-) message me or maybe you could post up a link ?

abo_hosni says:

Oct 30, 2010. 1:00 AM REPLY

Sure! Click on the " i " box above the image then download the original file. 7809 is a volt regulator whose output is +9 Volts

mellink says:

Oct 30, 2010. 9:31 AM REPLY

Thanks! Never seen that before :-)

tsuwah says:

Oct 7, 2010. 6:49 AM REPLY

can you wire this up to the speedo, water temp or fuel gauge? i imagined a Vader style gauge

abo_hosni says:

Oct 8, 2010. 3:33 PM REPLY

knight raider style :) , I'm planning to make one for the speedo when I have time. Other gauges would be easier for sure

keiou says: nice! good job. :)

http://www.instructables.com/id/DIY-LED-Tachomter-RPM-gauge/ 

Sep 26, 2010. 10:03 AM REPLY

agis68 says:

Sep 19, 2010. 7:23 AM REPLY

brilliant project...5/5

nickstewartroc says:

Sep 12, 2010. 7:45 PM REPLY

Would the circuit diagram and circuit change if used for an inline 6?

abo_hosni says:

Sep 13, 2010. 7:19 AM REPLY

No, only calibration (adjustin the trimpot variable resistance) will differ

nickstewartroc says:

Sep 13, 2010. 6:00 PM REPLY

Ahh ok i see now, thanks!

verdastel says:

Sep 8, 2010. 3:13 AM REPLY

Outstanding instructables. You can get money from this project.

abo_hosni says:

Sep 6, 2010. 7:42 PM REPLY I want to make a LED bar speedometer, too. I wonder what type of sensors to be used, magnetic or optical one? I will attatch t he sensor to the speed wire I have Then I need a schematic for 30 LEDs. can any one help?

NachoMahma says:

Aug 28, 2010. 7:36 PM REPLY . Great project. . Nice pictures. Thanks for knowing how to focus ;) . I would like the ability to dim the LEDs added to the circuit. A rheostat in the top line of your schematic might be all it takes. . I suppose anyone who could build this project can figure out where -ve is and that an ignition coil can kill you, but some generic hints would look nice in your instructions along with a warning about the HV side. . Keep up the good work. Do you have any plans for making iBles f or other gauges?

frollard says:

Aug 29, 2010. 8:29 AM REPLY How and where exactly to hook the zenzer t o the ignition can be tough to figure out -- I thought it'd be good to make a magnetic/vampiric t ap that just wraps around the ignition line and t hen boosts the EM signal so you don't have to actually touch the hv lines. The 3914 datasheet shows 'Output current programmable from 2 mA to 30 mA' **exerpt** "CURRENT PROGRAMMING A feature not completely ill ustrated by the block diagram is the LED brightness control. The current drawn out of the reference voltage pin (pin 7) determines LED current. Approximately 10 times this current will be drawn through each lighted LED, and this current will be relatively constant despite supply voltage and t emperature changes. Current drawn by the internal 10resistor divider, as well as by the external current and voltage-setting divider should be included in calculating LED drive current. The ability to modulate LED brightness with time, or in proportion to input voltage and other signals can lead to a number of novel displays or ways of indicating input overvoltages, alarms, etc."

frollard says:

Aug 29, 2010. 8:53 AM REPLY

To be specific -- whatever resistor you put on pin 7 will act as a virtual resistor on the led pins.

frollard says:

Aug 28, 2010. 3:17 PM REPLY That is a really cool pr oject! I could look it up -- but perhaps a description of how the circuit functions would be helpful -- My guess is the 3914's are cascaded vu analo meters, and the 2917 is a frequency counter?

abo_hosni says:

Aug 28, 2010. 3:29 PM REPLY 2917 is a frequency to voltage converter. 3914's are LED dot/bar display drivers. But you can't expect a more sophisticated description of the circuit from me, in fact I'm a surgeon with special interest in DIY projects, electronics etc... :)

kelseymh says:

Aug 28, 2010. 3:49 PM REPLY Definitely, please put that information (maybe a little bit more) into your Step 1. It will really help people who are not familiar with this stuff to learn something. This is an outstanding little project, and deserves good exposure and use! P.S. So when are we going to get an I'ble on DIY r esection? ;->

abo_hosni says: Done, is that enough to help? (about the DIY resection, I may make one instructable for it :D )

view all 53 comments http://www.instructables.com/id/DIY-LED-Tachomter-RPM-gauge/ 

Aug 28, 2010. 5:01 PM REPLY