Checking Tach

photofly · Post by **photofly** » Sun Jan 03, 2016 8:29 pm

NeverBlue wrote:Wtf???
Your digital tach proves it all!!

It is correct guaranteed...it's digital and going off the ignition.

I believe it just runs off the regular cable drive; for sure its not calibrated, so I do admire your sudden Damascene absolute confidence that it must be correct.

You've been keeping that all along?

No, not mine - just an aircraft I happened to be in this morning.

cgzro · Post by **cgzro** » Mon Jan 04, 2016 4:53 am

Photofly, I believe thats the same tach I have. RPM-1 by EI. It is digital and gets is pickup from the two P-leads. It has an RPM drop display when one or the other mag is grounded. No cable pickup that I'm aware of.

Impressive though to be able to check in flight.

NeverBlue · Post by **NeverBlue** » Mon Jan 04, 2016 5:21 am

Correct GyvAir,

Agenda here was to give some advice to Ahramin...but then I was forced to defend myself against that advice and it became a debate about they way that most here do an annual RPM check with non-calibrated equipment in a non-standard way.

I will not answer any of your questions GyvAir because I either already have in the thread.

...or I simply don't want to

And can someone please tell me WHAT AMO IS ALLOWED TO CALIBRATE THERE OWN TEST EQUIPMENT?....with a lightbulb....

NeverBlue · Post by **NeverBlue** » Mon Jan 04, 2016 5:24 am

It's not a mechanical tach....and it doesn't need cal.

And it doesn't agree with yours...big surprise...

photofly · Post by **photofly** » Mon Jan 04, 2016 5:51 am

It only reads to the nearest 10rpm- the last digit is always zero. So in which picture does it disagree with mine??

And why do you say this tach doesn't need calibration and mine does? I'm sure there's some logic in there but I'm unable to follow it.

Troubleshot · Post by **Troubleshot** » Mon Jan 04, 2016 10:36 am

NeverBlue wrote:...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 5566 times

cgzro · Post by **cgzro** » Mon Jan 04, 2016 11:19 am

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 · Post by **photofly** » Mon Jan 04, 2016 11:32 am

Sorry - it did indeed say 2570.

photofly · Post by **photofly** » Mon Jan 04, 2016 12:24 pm

: FullSizeRender.jpg (114.5 KiB) Viewed 5551 times

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

NeverBlue · Post by **NeverBlue** » Mon Jan 04, 2016 1:43 pm

...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 · Post by **GyvAir** » Mon Jan 04, 2016 2:54 pm

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

cgzro · Post by **cgzro** » Mon Jan 04, 2016 4:22 pm

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 · Post by **NeverBlue** » Mon Jan 04, 2016 8:44 pm

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 · Post by **NeverBlue** » Mon Jan 04, 2016 9:01 pm

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 · Post by **NeverBlue** » Mon Jan 04, 2016 9:16 pm

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 · Post by **Meddler** » Tue Jan 05, 2016 2:01 am

You guys are billing by the hour for this right?

jschnurr · Post by **jschnurr** » Tue Jan 05, 2016 8:58 am

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...

photofly wrote:It's a $1 4.000 MHz crystal.

Pshhh, you could get 11 for that price here.

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

Would $0.15 be too much?

photofly · Post by **photofly** » Tue Jan 05, 2016 11:11 am

jschnurr wrote: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.

photofly wrote: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

photofly wrote: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 · Post by **lownslow** » Wed Jan 06, 2016 9:28 am

photofly wrote:
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 · Post by **photofly** » Wed Jan 06, 2016 9:45 am

Sorry - they're all gone now.

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