how do i make an RPM reader

[panaroL]

sorry for this Q for i am really at lost
what is tachometer..what is ..what is.etc..i really dunno

well...how can i actually build a DIY RPM reader?

[Dan Baldwin]

A tachometer is a device that measures the rotational speed of something that it rotating. If you want any more help than that, we'll need some more specifics like what kind of output do you need? Do you want a meter to tell you how fast a prop is turning, or do you need an analog output to drive something else or ???

Dan

[panaroL]

ouh
hhe thanks a lot for replying
hehe
im going to measure RPM for a propeller rotational speed, which is powered by a fuel engine [UAV], so there is no electrical component on this engine

yup i wanna know how fast the prop is turning :)
id juz wanna read the output RPM either on digital meter [better if possible~ or analog]

[Daniel7866]

Analog way is basicaly a Frequency/ Voltage converter. I've used (and still use) the LM 331 from National Semiconductor. You need to have a sensor sending the frenquency info to the converter. Sensor can be phototransistor, hall sensor, mike, ...

Daniel

[Comatose]

With a pic, feed the output of an encoder to the INT pin. Increment a counter every time you get a pulse. Record how many pulses you get in one second.

[Acetronics]

Hi everybody

;) Somone interested in a 16F84 rev counter ??? 43 to 32000 rpm 2,3,or 4 blades 0.1% precision LCD 2x8 characters. and stable readings ...

Mail needed for all files ...grrrrrr even US forums are too small for a correct PCB !!! :D

Alain

PS: Tested and approved at the French scale championships ... Yeah !!!

[na-rc]

Would you pllease to sent me 16F84 rev counter chai@na-rc.com

[Acetronics]

Hi, na-rc .com

I do not think such a counter could work properly with 1/18 cars, as it needs blades ... note mods to allow more than 32 000 rpm are not so easy nor ... PCB has to be re-designed.

really sorry

Alain

[lazy-b]

Alain,
Nice Tacho Meter, Please send also at ellioncham@yahoo.com, I just wonder how sensitive is your sensor, I plan to measure that RPM of my helicopter, plan to installed the sensor at the mid-section of tail boom.

Circuit Posted by Daneil, is very effective, I have tried making the Analog Tachometer and use it on my car, I use a 270 degree Analog meter, use it on measure the Engine RPM, I just connect it at Ignition coil, during those day, car do not have engine RPM meter.

Thanks.

Ellion

[mike50]

Acetronics,

That 2x8 display looks like a Picvue PC064PYL. Do you know of a source for those? I have one that I got somewhere for about $5 US, but I would really like to get several more.

Mike

[panaroL]

hmm..i dont really know bout electronics..so..mail me also at fx_0220@yahoo.co.uk
well..if i get the mail..what do i do with em?
LM 331, 16F84 <--what are these btw..huhuh :confused:
any way i understand that id need an input for the electric circuits [izit?] that u guys are posting..where can i get em..n what are they?how do i setup them on my rig [im building a rig for my proj, so ill want to know the rpm the blades [propeller] are moving at]
btw, can i get some electiric/electronic shoppe to create the circuit u guys are posting if i just give them a printout?
thanx guys for posting :)

[Acetronics]

:) Hi, Mike

Those displays are simply on the Web shop from SELECTRONIC : http://www.selectronic.fr , on the other side of the channel ... ref 50.7887 costs 9.30 Euros.

Alain

PS: it seems they are manufactured by Xiamen Ocular Devices Co. probably in China ...

[Acetronics]

:D
Hi, Lazy-b

Sensitivity is self-adjusted to ambiant conditions ... note first stage also accepts LDRs without any adjustment.

If you want more about the scheme or program, don't hesitate.

Alain

[Acetronics]

Panarol,

Sorry to tell you that, but you'd better buy a "ready to use" tachometer from your local model dealer ...

and begin with simpler schemes ...

Alain

[mike50]

:) Hi, Mike

Those displays are simply on the Web shop from SELECTRONIC : http://www.selectronic.fr , on the other side of the channel ... ref 50.7887 costs 9.30 Euros.

Alain

PS: it seems they are manufactured by Xiamen Ocular Devices Co. probably in China ...
Thanks Alain. The display itself looks to be exactly what I had, but the electronics behind it (I got the datasheet from the Selectronic site) are different. This has a parallel interface, the one I have has a synchronous highspeed serial interface.

Mike

[raymcm]

Panarol,

Sorry to tell you that, but you'd better buy a "ready to use" tachometer from your local model dealer ...

and begin with simpler schemes ...

Alain

Or for a heli, buy a "wireless" bicycle speedometer and calibrate the "wheel" size to read RPM, you can have a head speed indication on your tx .. loads of info on runryder.com (hope I can post that here ??) which involves mounting a small magnet on the main gear wheel and positioning the sensor close to it.

[Acetronics]

Hi, Ray
Very good idea, but I wonder if a bicycle wheel can reach 1500 rpm ... ~ 100 mph???
- Lance Armstrong will have a lot of work to win the " tour de France " this year ...

Alain

[raymcm]

Hi, Ray
Very good idea, but I wonder if a bicycle wheel can reach 1500 rpm ... ~ 100 mph???
- Lance Armstrong will have a lot of work to win the " tour de France " this year ...

Alain

Yes, the cheap one I bought went to 199.9

There is already a lot of info out there on this subject.

[Acetronics]

:) OK ... seems right.
Just program ~ 1 yard dia. wheels.

nice idea, i'll look for speedos showing over 100 mph or Km/h ... ( I have'nt seen yet hereby ...)

Alain

[lazy-b]

Yes, its a great idea using a Bicycle Odometer to measure a rotor RPM.......been thinking of using a Bicycle Odometer to put it in my car, cause my car do not have a resettable odometer/trip meter.

Ellion

[ZAGNUT]

hey mayo, i would also like to see your tacho files. please mail them to zagnut@walla.com

thanks,
dave

[Uitgeslapen]

nice

[Abbo]

Can you please send me the files for the tacho too??

babdy75@bigpond.com.au

Cheers
Brett

[master_007]

Hi,
i also would like to see your tacho files. please mail them to h.kreso@gmail.com

Thx, regards

[tomskk]

Hi Alain,
any chance of getting those tacho files. Please mail them to softlab-mt@siol.net

Thx again for your help before.

[nicholastr]

please mail them to nihatkilictr@hotmail.com
thanks.

[warren52nz]

I just posted an article today on this:

http://www.rcgroups.com/forums/showthread.php?t=438740

You can determine the rpm if you determine the note coming off the blade. I use this for my helicopter but it would work for a plane propellor too.

Once you determine the note in Hertz (cycles/second) you multiply by 60 (seconds in a minute) and divide by the number of blades on your prop (2 or three probably).

Best of all, it's free!

Hope this helps.

[Malc C]

Hang on.. I'll just un-plug and cart the PC to the flying field.... now all I need is to get some mug to hold a Rappy close enough to the speakers to hear when the tones match !!!!!

Sorry Warren, couldn't resist pointing out the limitation of that device ;) Might be hine for small indoor micro heli's or electric props, but not really practical for glo powered props or large helicopters

[ZAGNUT]

same type of program has been used for a few years now to measure RPM of fast glow planes in flight. make a few low passes over a tape recorder with mic, then check the RPMs for various props tested at home on the PC.


dave

[lazy-b]

guys: have read someone able to use a digital camera with adjustable shuttle control to get the RPM of the Helicopter. getting the Shadow created by the rotor blade in degree divide by 360 and multiple it by shutter speed you can compute for the Rotor RPM.

I have not done it, cause my Digital Camera do not have the option to control the shutter speed.

I just notice, if I use a cheap low cost digital camera, I can see the shadow create by the rotor blade, I guess, the low cost digital camera has a much slower capture time.

If I can only know the shuttle speed of my digital camera, I can approximate the RPM made by my Bell 222.

its better to adjust the shutter speed of your digital camera such thats it will give a bigger shadow angle.

lets assume my Ecureil helicopter has a shadow blade angle of 15 degree.

RPM = Fraction of Revolution X Shutter Speed X Convertion Factor
RPM = (Angle/360) x (Shutter speed) x 60 sec/1 mins
rpm = 15/360 x 480 x 60 = 1,200 rpm

any one of you has a digital camera with adjustable shutter speed? I guess, you can experiment it using your airplane propeller, Just measure it with standard tachometer, then take a picture of it using your digital camera, then you compare its reading.

[lazy-b]

Dave: that was a better Idea, just measure the engine sound, and you can determine the RPM of Engine.

I guess its also applicable in helicopter, just get the RPM of the engine and divide it by the the Gear Ratio of the Main Rotor Gear to Clutch Gear.

Its a lots better than Viewing ur Helicopter thru a Sloted OPTICAL Disk with Tachometer.

Just need a small Mic and Pic controller.

Has anybody have make such a project?