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Old 05-07-2008, 01:00 PM   #1
Finless
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Default FREE - RC Heli Optical Tachometer DIY

OK Helifreak user mikef had posted about this home made optical tach some time ago. Many asked for plans and instructions for how to make one. Mike has now made that available for download here on Helifreak.

I myself have not built this myself but looking at the plans / design it looks very sound. It works just like many RC Heli tachs where you look through a view finder and adjust until you see the blades stop. This is a PROPER heli tach design not a airplane prop tach design.

Mike agreed to answer any questions you all have on the design or building it.

Thanks Mike! You Rock!

Here is the link to download the plans and code.

NEW FILE UPDATED 6/6/2008
Download Link -> RC Heli Tach (1 Megs)


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Last edited by Finless; 06-06-2008 at 09:56 AM..
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Old 05-07-2008, 01:36 PM   #2
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I agree that the concept is sound and, being an EE by degree and a software engineer by trade, I don't see any glaring errors. It's pretty ambitious, though, meaning that I probably couldn't make the time to build one.
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Old 05-07-2008, 01:47 PM   #3
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Nice idea ! BTW i doubt many people have or have access to a PIC programmer however i have found an easy and CHEAP solution. RCD PIC programmer (Google it) only uses passive parts and costs about $10 to make. Here is the one i throw together (yes iam aware its very ugly but it works).


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Old 05-07-2008, 02:04 PM   #4
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Old 05-07-2008, 02:28 PM   #5
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Would Mike or anyone else be willing to pre-program the PIC Micro Chip and mail out to us Freakers? For a fee of course...say $8-12 with chip and shipping.

I would really like to build one of these as I'm always looking for a project. However, buying a programmer seems to kill the cost benefit of buying a tach outright. Plus, I have no use for the programmer afterwards.
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Old 05-07-2008, 02:35 PM   #6
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Quote:
Originally Posted by HFG View Post
BTW i doubt many people have or have access to a PIC programmer however i have found an easy and CHEAP solution. RCD PIC programmer (Google it) only uses passive parts and costs about $10 to make. Here is the one i throw together (yes iam aware its very ugly but it works).
Is this it? It looks like the parts count is about the same. I agree with your $10 assessment.

http://feng3.cool.ne.jp/en/rcd.html
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Old 05-07-2008, 02:42 PM   #7
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Quote:
Originally Posted by HFG View Post
Nice idea ! BTW i doubt many people have or have access to a PIC programmer however i have found an easy and CHEAP solution. RCD PIC programmer (Google it) only uses passive parts and costs about $10 to make. Here is the one i throw together (yes iam aware its very ugly but it works).
Great idea...but I'm stupid when it comes to any programming type stuff. Is the code for the chip hard to write?
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Old 05-07-2008, 02:52 PM   #8
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Yes thats the RCD programmer i used. Nice thing about it is that it generates the 12V required to program the PIC directly from the serial port. Jesse there is NO reason to write any code. Inside the files provided by MikeF is a file called TACH.HEX. The hex file is what you program to the PIC.

Programming a PIC is its MAJOR disadvantage for hobby use IMO. This is why i have started using Atmel controllers which you can use USB to program them.
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Old 05-07-2008, 02:59 PM   #9
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Yes thats the RCD programmer i used. Nice thing about it is that it generates the 12V required to program the PIC directly from the serial port. Jesse there is NO reason to write any code. Inside the files provided by MikeF is a file called TACH.HEX. The hex file is what you program to the PIC.

Programming a PIC is its MAJOR disadvantage for hobby use IMO. This is why i have started using Atmel controllers which you can use USB to program them.
Ohhhh yeeeaaah, It's still early here in HI and I worked late last night. I got so excited, I didn't look at the rest of the files in the zip. Thanks man! But still, rather than build a programmer too, I'd rather just buy a chip from someone if at all possible...
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Old 05-07-2008, 03:32 PM   #10
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I would be willing to program the chip for you freaks if you have no way of doing it yourself. You guys buy your own chip and just mail it to me. I would program it for free and you just cover the cost of all shipping. I will test it before I send it back. I would think you could ship this via US postal for $1 or less? How does that sound? You can PM me or email me when you get your chip and I will send you my address. ZIP is 48453 if you guys want to calculate shipping. That $10 programmer looks pretty cool HFG. I might build one just to have an extra programmer around.

I also apologize for the half year it took to get this info out. I get side tracked easily and have multi projects going all the time….. If you guys have trouble with the write-up please let me know. I wrote it from memory and it could have typos (I hope not however). Also if anyone has a suggestion for improvement let me know and I would gladly add it to the write-up. The code I used was just what I came up with and since I am not an expert programmer, there might be a better way. So far the prototype is still working fine. (Rond is the current owner).

Thanks,

Mike
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Old 05-07-2008, 03:44 PM   #11
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You got it Mike. I'm placing my order for parts today! Thanks man!
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Old 05-07-2008, 09:29 PM   #12
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This tach works awesome. Mike calibrated it for a range of up to just over 4,000 rpm!! The first time I took it out at the field and used it on my T-Rex 450 V2, one of the guys with his new MinAir 3000 rpm heli tach still couldn't get my Rexy, but this one locked it in easily.

This is not the only cool thing Mike has made either, he has a shop full of cool stuff like this, not to mention an awesome altimeter. Look at post number 27 of this thread

http://www.helifreak.com/showthread.php?t=61615&page=3

for a pic of the altimeter that was actually made by mikef and flown by me and Jason.

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Old 05-07-2008, 09:49 PM   #13
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Nice to see there is some interest in DIY electronics.... its inspiring
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Old 05-08-2008, 10:27 AM   #14
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Ok I think I'm going to have a go at this. Should be fun.
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Old 05-08-2008, 10:36 AM   #15
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The circuit for the hold button is missing!!!!
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Old 05-08-2008, 10:46 AM   #16
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Yep it sure is... It doesn't show you where the memory button should hook to on the PIC.

Mike?

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Old 05-08-2008, 11:04 AM   #17
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I am at work right now but when I get home today I will check that out. It just connects to one of the pins on the PIC chip.
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Old 05-08-2008, 11:18 AM   #18
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Looks like Pin 15 on the photo (don't feel like following your ASM code). Should just be a button and a pull up resistor (this goes from the pin to VDD).
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Old 05-08-2008, 12:58 PM   #19
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I'm having trouble finding a 2.5K Ohm precision pot. Will any 10 turn pot do?
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Old 05-08-2008, 01:05 PM   #20
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Dont think i have EVER heard of a precision pot More turns the better. a 20 or 25 turn pot will work, its just a voltage divider.
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