LED bar graph Tach

[Johnfiat]

I know that this topic has been beat to death. I’m looking for a LED bar graph tachometer circuit that will display the RPM like they do on the F1 and endurance racecars. I know that I found a circuit posted before, but I’ve can’t find it no matter what search I use. I know that it had one row of LEDs, I would like it to have two rows that meet in the middle. Any help would be great.

Thanks

John Whitney
Wis X 1/9

 

[williB]

if you click on search ( upper right)
and put in

brake and light

or

tail and light

there is a lot in there..

 

[jbeng]

Are you ok, williB? I think that's another thread ...
Johnfiat, I think you might be looking for the LM3914. It's a bar graph display driver which gives a linear response output. (vs the LM3915's log output). My search of the archives gave 70 threads which had something to do with the LM3914. You should find something there ...
JB

 

[williB]

a while back the LM3914 was suggested for a guy with a motorcycle brake light question ..
that was what i was referring to.. thanks.

 

[jbeng]

Sorry, williB. I thought you might have meant to reply to this thread, where firedog25 was talking about auto taillights.
JB

 

[musthave]

led bargraph tach

Hi I have a full circuit diagram of a digital tach you can have a look here there are 6 pages
personal.nbnet.nb.ca/alaindes/digitac1.jpg
personal.nbnet.nb.ca/alaindes/digitac2.jpg
personal.nbnet.nb.ca/alaindes/digitac3.jpg
personal.nbnet.nb.ca/alaindes/digitac4.jpg
personal.nbnet.nb.ca/alaindes/digitac5.jpg
personal.nbnet.nb.ca/alaindes/digitac6.jpg
cant get the url to link directly sorry.

 

[pittuck]

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[gbyzf1000]

:cry: :cry:
the links are cut off......
can y inform me where can i found out the circuit??

ty.. :lol:

 

[Joel Rainville]

:cry: :cry:
the links are cut off......
can y inform me where can i found out the circuit??

ty.. :lol:

**broken link removed**

[Edit: That's not it at all, sorry Nifty brake light though :lol:]

 

[gbyzf1000]

:cry: :cry:
the links are cut off......
can y inform me where can i found out the circuit??

ty.. :lol:

**broken link removed**

[Edit: That's not it at all, sorry Nifty brake light though :lol:]

ty for yr responce... ,
although is any way to find the cirquit regarding the LED bar graph tachometer ?

 

[musthave]

I have it in files not on the net as my web site is full of other material.
i will try to find it and post it again or email it would be better as i will have to delete material out of my site to post it again.
so let me me know your email addresse.

 

[Joel Rainville]

I have it in files not on the net as my web site is full of other material.
i will try to find it and post it again or email it would be better as i will have to delete material out of my site to post it again.
so let me me know your email addresse.

You could simply attach them to your next post...

 

[musthave]

there very large file size like 1.7mb to 2.3 per page and there is 7 page,
im trying to open my tripod site but its been a while so im having problems finding the login and passwrd.

 

[musthave]

ok got it
deleted doesnt work

 

[musthave]

S$%^$ tripod dont hallow remote links will have to make an html page see
what i meant email would of been easyer. so diregard the above post it wont link to the files..

ok try this here **broken link removed**

 

[Klaus]

John, can you elaborate on the "two rows that meet in the middle" bit? it does not quite give me a mental picture. One row, yes, one circle, yes but TWO rows??
Anyway, here's some practical advice how I made such a tacho many years ago...
I used 3 LM3914's cascaded, got the circuit from the application notes of that IC.
I used 60 green LED's, every 5th was red to indicate 1000RPM, so it had a resolution of 200RPM per LED. This was quite a long display, even when using 3mm round LED's. If you use the row type assembled LED strips it will be even longer.
I do remember that driving the tacho accuately was trickier than making it. LM2917 springs to mind, tapping into the ignition circuit. Had to use an oscilloscope to calibrate the circuit.
The tacho still sleeps in my junk box now, sold the car (Honda CIVIC) a long time ago and the new transport has a tacho already.
Klaus

I know that this topic has been beat to death. I’m looking for a LED bar graph tachometer circuit that will display the RPM like they do on the F1 and endurance racecars. I know that I found a circuit posted before, but I’ve can’t find it no matter what search I use. I know that it had one row of LEDs, I would like it to have two rows that meet in the middle. Any help would be great.

Thanks

John Whitney
Wis X 1/9

 

[audioguru]

Two rows of LEDs that meet in the middle?
You can make a tach from an LM2907 or LM2917 as an RPM to DC voltage converter. Then you use an LM3914 as a bar-graph voltmeter.
To get two rows that meet in the middle you put each partnered LED in series with the other one, for each output of the LM3914. :lol:

 

[Klaus]

Two rows of LEDs that meet in the middle?
You can make a tach from an LM2907 or LM2917 as an RPM to DC voltage converter. Then you use an LM3914 as a bar-graph voltmeter.
To get two rows that meet in the middle you put each partnered LED in series with the other one, for each output of the LM3914. :lol:

Thanks Audioguru, I wish it would make sense now but it still doesn't
Maybe I'm dense today and need to take more tablets :lol:
Anyway, here is how I imagine two rows:
1. one row above the other
2. one row at right angles to the other
3. one row next to the other

the "meet in the middle" bit could apply to option 3 but then you end up with ONE row.
When you mention partnered LED's, are you talking about two PARALLEL rows of LED's?

The tacho I built had a single long row of 60 LED's, connected, in the bargraph mode. The more LED's were lit, the highter the RPM.
I simply cannot imagine how to display RPM on TWO rows that meet in the middle and still make sense of it.
Or do I miss something here? A sketch would be appreciated :wink:
Klaus

 

[audioguru]

It doesn't make sense to see two rows of LEDs that meet in the middle.
I was thinking of two rows at right angles or straighter, and the two LEDs on the ends are wired in series to #1 output of the LM3914, then the LEDs beside them are wired in series to #2, then all the way towards the middle so all LEDs are lit at max.

 

[musthave]

I think this is what he means
**broken link removed**
did any one saw the circuit previously posted would that work at a fast speed .