DIY Tacho coz I woz BORED LOL!!!

[Mark J]

Hi guys,

Just a little tinkering im doing at the mo as bored as cant go and fly because of the 'great' british weather, so decided to have a play as I remember seeing a thread somewhere on a DIY tacho, so thought id have a go.

I managed to find the old thread on helifreaks and used it as the main basics for mine, although I rewrote the code for the PIC chip as I didnt have the same chip as they used , so I used a PIC 18F2455 which I had laying around from when I made a temperature controller for my old marine tank.

So far ive got the chip and LCD hooked up on a breadboard with the IR sensor and reciever and thats working nicely, and at the mo seperate is the main motor setup which uses 2 pot's to fine tune the rpm's of the motor.

I made a VERY rough disk out of card and cut 2 slots in it and held it in place while looking at the screen and so far so good! it's counting the RPM's nicely.

So tomorrow, will see about bringing it all together into a nice little package and will go into more details on how it works (along with pics!)

so far, id say its cost around about £15 give or take a few quid and wont cost much more as only thing I really need to get is a nice little box for it all to sit in.

Fair bit cheaper than the ones ive seen online etc, and this one dosnt show a 3 figure number and ask the user to multiply it by 10 to get the RPM

So the crap weather does SOMETIMES have its benefits (but we're talking SERIOUS borderline on that as id rather be out flying LOL!)

Mark.

[Rotorhead]

Cool, now just add some code to drive a servo and you should be able to turn it into a governer with a bit of tweaking hehe.

I've been getting back into pic programming again, still doing it in C via MPLAB aswell, its a lot of fun, funny you mention doing it because of the bad weather.

[Mark J]

LOL! cant be arsed with all that stuff! just a nice simple (simple he says! LOL!) project to while away the days while the summer skims past us AGAIN!

[Mike W]

make me one then Mark

[Mark J]

hehehe... let me get this one working fine first m8y lol!!

I just this second thought of something that would be cool for them!

*IF* I made more I could personalise them so that each one says 'Property of ..........' so that if anyone lost it etc, just turn it on and VIOLA! got the owners name

BUT thats if I did make more, as when its done would have to do a breakdown on costings etc to see how much each unit would cost to build etc.

Mark.

[Heli8or]

Was thinking of doing same using a Bicycle Tachometer/Speedometer with a big readout and a max speed capability. Attach magnet to main gear, sensor on a bracket fixed to main frame under main gear and readout where you can see it. Set rotor diameter instead of wheel diameter and of you go. Take off and hover, land and check max speed, climb out and do same. Bit of maths to change MPH into RPM and your done.
But when i get around to doing it, (couple of years time) i will probably be able to tell the head speed by ear.

[xygax]

You know it needs blu tooth for dynamic feedback ov actual RPM and adjustable dampening so it dosent make teh engine pulse....I think a full colour graphic display so you can see what it was doing for the whole flight and maybe a video MP4 compression so you can retrive the whole fright to the screen when you land...

Now that would be special.....

oh and live streaming via zigbee..

Steve

[GizmoB73]

You know it needs blu tooth for dynamic feedback ov actual RPM and adjustable dampening so it dosent make teh engine pulse....I think a full colour graphic display so you can see what it was doing for the whole flight and maybe a video MP4 compression so you can retrive the whole fright to the screen when you land...

Now that would be special.....

oh and live streaming via zigbee..

Steve

That's just ridiculous...


It should be a DLNA server over WiFi so you can view it on your PS3 or XBox...

[Mark J]

Lol!!!!! heres a stick and youve got the wrong end of it LOL!!!!!!!!!!!!!!!!!!!!!!

the tacho is a hand held jobby that you stick up against your mush and peer through it to get the headspeed etc!

A normal one attached to the engine fan etc would be easier lol, as then its a simple count the pulses as it rotates in say a second then multiply by 60 to get the RPM (therabouts lol) but the hand held ones are a little bit more involved as you have the disk with so many slots in etc, and then measure the pules as you look through etc, then calculate the disk pules per second and then do some weird voodoo to get the disk pulses (depending on the slots on the disk) to the main blade RPM but not a 360 full turn on the blades but a 180 snapshot!!!! its fried my brains today doing the maths and im CRAP at maths LOL.

[xygax]

ok... so put two sensors on one on engine for govener and one om main gear for head speed....

Maths is easy.... use multiples of two as far as posible .... make your clock an easy number (32 seconds)... then shif right five times is divide by 32... 18's got hardware divider anyway...

STvee

[xygax]

Quick and dirty taco.

1. Use int on change (B0) for the sensor input
2. Set up a 1 second int using TMR1 (it will serve as an internal clock to process the count
3. Set up counter to count B0 events within the ISR it will be cleared by the math later
4.

[xygax]

Quick and dirty taco.

1. Use int on change (B0) for the sensor input's. enable this and make ISR inc 16 bit counter
2. Set up a 1 second int using TMR1 (it will serve as an internal clock to process the count and do math)
3. Set up counter to count B0 events within the ISR it will be cleared by the math later
4. Set the main routine to run once per second on the tick generated by<2> above
5. Copy counter to temp and clear counter (incase an event occours during maths)
6. Math. *60 is (*64)-(*4) or a 16 bit(probably) RLF function.
a. RLF,RLF,save *4,RLF,RLF,RLF,RLF,-save*4 is *60
b. use a rolling 2 sec ave to smooth the display (old + current / 2)
c. Bin to BCD.... (packed 2 digits / byte)
d. PBCD to ASCII > display

[Mark J]

ouch my head is hurting reading that this early in the morning m8 LOL!!!

have absorbed it, and my brain will gradually work through it as the day progresses

Mark

[Mark J]

ok sorry for no updates, but been tweeking and i need to get a better adjustment pot that has multiple turns as the standard 1 turn pot dosnt allow a fine enough change in the rpms etc but the main reason for no pics as yet is our camera decided to quit working (gears in the lens mechanics gave up and just click annoyingly before the camera beeps and turns off!) so waiting on delivery of our new camera so I can get some pics of the breadboard.

I did take a pic with our really old camera to show to Steve (xygax) but its pretty poor quality and out of focus a bit, so will wait for the new camera to arrive in a couple of days.

Mark.

[Stuart]

I did this years ago, using a bicycle tacho. There was a guy who posted a method for using a bike tacho and it gave a boom mounted readout.

The only problem being it was pretty pointless in the end your 50ft inverted and you can't see it. What you want is the RC Spartan glowing daylight blades that display the headspeed while your busy tic toc'ing etc... Now that would be cool.