TTL Signal Generator?

I've been searching google for a TTL level signal generator schematic to simulate an input to a tachometer.

Ideally this would be outputting something like 50 or 60 Hz to fool the µC into thinking it had a 3000 or 3600 RPM speed counting device connected to a digital input.

Pointers to relevant reading or schematics please.

Thanks.

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M.S.

Sure, just check out and use the Tone library, it's really just a TTL frequency generator function:

http://code.google.com/p/rogue-code/wiki/ToneLibraryDocumentation

Lefty

Thanks gents. That is what I am looking for. I found a similar circuit in the 555 cookbook but was concerned about the output potentially being over 5V thereby cooking my poor little Seeeduino.

I just realized I may not have been clear. This will be a signal applied to a digital pin as input to an Aduino as the core of a tachometer circuit. Rather than actually running a noisy and potentially dangerous machine with the actual IR speed sensor connected. I would like to simulate that input for testing and development of the tachometer.

As I am using a digital input pin I do not wish to damage the mega168 with more voltage than it’s designed for. Hence the desire for a TTL level circuit.

Thanks. Sorry I should have given more details.

I just realized I may not have been clear. This will be a signal applied to a digital pin as input to an Aduino as the core of a tachometer circuit. Rather than actually running a noisy and potentially dangerous machine with the actual IR speed sensor connected. I would like to simulate that input for testing and development of the tachometer.

As I am using a digital input pin I do not wish to damage the mega168 with more voltage than it's designed for. Hence the desire for a TTL level circuit.

Thanks. Sorry I should have given more details.

All the more reason to just use the tone library I posted about. It will output a continuous ttl level square wave at whatever frequency you wish. Just wire that output pin back to one of the Arduino digital input pins and you are free to develop your tachometer portion of the sketch.

Lefty

This will be a signal applied to a digital pin as input to an Aduino as the core of a tachometer circuit.

Use the Tone library to generate the frequency you need and feed the output back into the Arduino pin of your choice. No need to build external circuitry for this.

All the more reason to just use the tone library I posted about. It will output a continuous ttl level square wave at whatever frequency you wish. Just wire that output pin back to one of the Arduino digital input pins and you are free to write your tachometer portion of the sketch.

Dammit! I can’t possibly do it that way. It’s -too- easy! ::slight_smile:

I’ll give it a try. Thank you.

Dammit! I can't possibly do it that way. It's -too- easy!

Hehe, must be an Oklahoma thing, we here is California are a little more laid back and lazy. :wink:

Lefty

If you wanted things real easy, you would probably want something like this:

http://www.dealextreme.com/details.dx/sku.18239

Noted that I double posted "retrolefty" on using the tone function within a few seconds and realize you're in the best of hands.

If you wanted things real easy, you would probably want something like this:
http://www.dealextreme.com/details.dx/sku.18239
Noted that I double posted "retrolefty" on using the tone function within a few seconds and realize you're in the best of hands.

Heh. Acquisition might be easier (I own one of those) but it's use is a PITA. The spinning object needs a bit of reflective tape for the thing to work accurately and you need to have a free hand to use it.

I've done much experimenting with that laser tach in my workshop and while useful it's just too bothersome to use every day.

While more complex to produce, the device I am working on is far simpler to actually use. Stupid simple actually. Just turn on it's power. Read the display.

Thanks for the help and suggestions.

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M.S.

(OT)

... was concerned about the output potentially being over 5V thereby cooking my poor little Seeeduino

sigh This is a runing gag - isn't it?

Just wanted to say thanks. I have my code working now. I went and built the 555 based oscillator.

(I had the parts and there's no code to clean up later)

It works as I was hoping it would. I just need to finish building the photoreflector circuit and draw up a PCB.

The little PCB I made with the 555 will also allow me to test these tachs once assembled prior to shipping.

Thanks again. This was a fun project and now I'm hooked on these Arduinos!