# Help to convert sine wave to square wave

Discussion in 'General Electronics Chat' started by JLourenco, Sep 27, 2012.

1. ### JLourenco Thread Starter New Member

Sep 27, 2012
3
0
Hello friends

I need one simply help, from you.

I would like to resused one old Tachometer from my car, but due to the fact of the car don´t have any sensor, I was thinking to use the alternator that it gives 210Hz at 750rpm it gives, for max rpm 5000rpm it gives 1290Hz. Amplitude is ~16V.
Now the tachometer accepted square wave whit 12V at maximum scale 7.000 rpm whit 233Hz, so for example the 3.100 rpm should be 103Hz: like the photo.

http://i236.photobucket.com/albums/ff166/PhantasticPhoto/img_3262_rs2.jpg

So my question, how can I make one simply wave converter whit frequency adapter, use the IC 741, but looks I can only have the same frequency?

Thanks,

JL

2. ### Dodgydave Distinguished Member

Jun 22, 2012
4,980
744
Last edited: Sep 27, 2012
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3. ### crutschow Expert

Mar 14, 2008
13,003
3,232
Not true. The alternator RPM is directly linear with the engine RPM (even though the alternator is going at a higher speed).

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4. ### ErnieM AAC Fanatic!

Apr 24, 2011
7,386
1,605
Any simple single transistor amp would work. It inverts the signal but that should not be an issue here.

(Sorry I don't have a nice figure handy to paste but probably someone else will in the next 5 minutes.)

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5. ### THE_RB AAC Fanatic!

Feb 11, 2008
5,435
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What is "whit"? Is that some silly ghetto slang for "with"?

Do you want to do frequency conversion? It sounds like it from trying to read your post.

If you need frequency conversion then it is a lot more complex than just trying to turn something into a square wave. There are lots of commercial speedo and tacho frequency converters on the market, probably about \$80 to \$90.

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6. ### JLourenco Thread Starter New Member

Sep 27, 2012
3
0
Thanks guys,

For all your help, one question guys, if I use the 555 timer like Dodgydave say, can I adapted the frequency? what component should be variable?

Yes I supposed the frequency is linear on the alternator also the voltage is all the same 16V.

Sorry guys I now that I have see that Automotive projects are forbiden, but I suppose, If I am wrong please acceptes my appologies, that the forbiden is to unlegal projects, like copy electronics keys, etc etc...that is not my problem I dont want to do nothing ilegal, just a simple project to convert sine wave to square wave (pulse wave) and speciality to adapted the frequency to put my old tachometer working...

7. ### JLourenco Thread Starter New Member

Sep 27, 2012
3
0
Sorry friend,

My native language is not english is portughese, sorry my mistakes.