Checking Tach

[Troubleshot]

...because yours is a piece of "test equipment" that you are using to do part of an annual with.

...and that aircraft tach is not a mechanical drag-cup type...


and yours reads 2470 and the aircraft reads 2410...nice try on the angle though...

And this is what it has come down to folks...top has been cut off a number and no surprise NeverBlue is focusing on that to prove some point...Please PM Avcanada to get this guy out of here. I mean really though, this like a 13 year old girl bullying another girl by saying she smells bad etc...no substance, all yapper

tach.JPG (65.53 KiB) Viewed 5568 times

[cgzro]

Just going from memory the little green led that is lit looks like the the 2550 - 2650 led position..
So 2570 would be the most likely digital value displayed on the LCD.

[photofly]

Sorry - it did indeed say 2570.

[photofly]

FullSizeRender.jpg (114.5 KiB) Viewed 5553 times

Six more, tested and ready to be sent to those people who asked for one. Should be in the post tomorrow.

[NeverBlue]

...the green led is on in the correct place for over 2500 RPM...you can't tell if it's 2510 or 2580 from the LED.

http://www.chiefaircraft.com/ei-tach.html

Why the different angle then?

and you don't know if the aircraft tach is within 9 rpm or 1 rpm of the optical one do you?

or in the case of the other two shots...within 4 rpm or 14 rpm?...3 rpm or 13 rpm?

[GyvAir]

Ahramin? Sulako?
This guy has all the charm and usefulness of a stuck mic on frequency.

[cgzro]

Think those LEDs change on the 50 not 100. That was my point. The last is above 2750 previous above 2650, previous to that above 2550 etc. Without going flying I cant be 100% certain but I believe thats what they do. Otherwise the increments are not even. Anyway Photoflys word is good enough for me.

[NeverBlue]

The digital tach is 10rpm resolution!

What is so wrong with what I am saying here?...and why is it different than what photofly is doing? Just because you don't agree??? Really??

[NeverBlue]

If they switch at 2550 like you say...then count back on the pictur i linked...your math doesn't seem to work very well...

[NeverBlue]

green led that is lit looks like the the 2550 - 2650 led position.. 
So 2570 would be the most likely digital value displayed on the LCD. 

Hah.

It's the only picture he took that cuts off part of the displayed numbers. So "most likely" he is trying to hide something.

What do you think about that??

[Meddler]

You guys are billing by the hour for this right?

[jschnurr]

Photofly:
Great work on the DIY'd tach. Would you be able to share the schematic and code? Did you use an AVR or PIC? I suppose it's simple enough, but I'm just curious how you filtered and stabilized the signal before feeding it into the microcontroller...

It's a $1 4.000 MHz crystal.

Pshhh, you could get 11 for that price here.

No extra switches- this is about minimal components, and three position switches are $0.70.

Would $0.15 be too much?

[photofly]

did you use an AVR or PIC?

PIC. Can you get 12 I/O pins on an AVR for $1? I have no idea.

I suppose it's simple enough, but I'm just curious how you filtered and stabilized the signal before feeding it into the microcontroller...

You're right... it's so simple I'm not going to waste your time by telling you how I did it. That's how simple it is! The code is even more trivial: two finite state machines, one to bang through the digits and the other to count the blades. Plus some 31 bit integer arithmetic.

It's a $1 4.000 MHz crystal.

Pshhh, you could get 11 for that price here.

Handy. If you live in Bangkok. If you live in Toronto however and you want one this afternoon (as I did, back then) then you'll pay $1. Which is why I described it as a $1 crystal.

Here they're even cheaper: http://www.aliexpress.com/item/Free-shi ... 94570.html

No extra switches- this is about minimal components, and three position switches are $0.70.

Would $0.15 be too much?

One thing I have learned is never to buy cheap connectors, cheap switches, or knock-off semiconductors. They *always* give you more trouble than they're worth. Plus I'm also out of pins on the microcontroller and I can't be bothered to use a bigger one or do some crazy charlieplexing stunt to suit the few people who both have three blades and are too dumb to multiply by two and divide by three. Soz.

Right back at you.

[lownslow]

FullSizeRender.jpg

Six more, tested and ready to be sent to those people who asked for one. Should be in the post tomorrow.

I got here late and can't scan the whole thread let the boss catch me not working. How does one get one of these nifty new PhotoTachs?

[photofly]

Sorry - they're all gone now.

[lownslow]

Darn. Oh well, I still applaud your effort for just going out there and making them for the hell of it.

[rmcdonald03]

Photofly, your project is awesome!

Also, do you plan on releasing a full schematic and maybe even a board layout? Or maybe making these for sale?

I built my own sampler and display board with an Arduino, but I can't seem to get the light pickup right. I'd love to see how you are cleaning up the signal coming from what I assume to be a photo transistor. I can't reliably find the rise and fall on my system unless I strobe the thing with a high contrast flashing light source.

-Ryan

[JasonE]

Works great! Thank you very much.

[photofly]

Now it's summer, I've noticed the photodiode tends to saturate when used against a bright sunny sky. I think the solution is a short piece of black tubing around it. I'll find something that works and mail it to anyone who's noticed the same thing.

[ahramin]

Shrinkwrap perhaps?