Digital Measuring Tape

I always was thinking of a measuring tape that never ends and be able to measure very long things. So I decided to make a small odometer and use it as a digital measuring tape.
I used a PIC16F819 microcontroller and a sensor from an old computer mouse (the remaining parts of one of my other projects Crazy Mouse) to make this simple measuring tape.
Do you want to make yourself? If yes read the rest of this instructable.

Step 1 What you need

To make this measuring tape you need the following components and tools:

• Printed circuits (find files in the next step)
• Copper board
• Sandpaper
• Iron
• Circuit board acid
• 1mm drill
• Soldering tools
• 1x PIC16F819 microcontroller + socket
• An old mouse (or one of its IR shaft encoders)
• 3x BC547 transistors
• 3x common anode 7 segments
• 1x 100uF electrolyte capacitor
• 1x 470ohm resistor (1/8 watt)
• 7x 10k resistors (1/8 watt)
• 2x Simple push buttons
• 1x Simple switch
• 2x AA batteries with a battery holder
• 1x Wheel (+ maybe some gears)
• A box for this measuring tape

Comments

[pmounica]

how long does it took to finish
can ii do it in less than a 3 weeks

[vahid_you2004]

If you have all things needed, you can do it in a day.

[farzadbayan]

Kheyli jaleb bod vahid jan !

[vahid_you2004]

thanks

[agis68]

cool project but you should do professional job in appearance. It seems like done with caveman tools...lol

[vahid_you2004]

Yes, I do it with caveman tools!!!!!!!!

[agis68]

I thought so!....(no offence)

[mdog93]

you might want to calibrate it on as long a distance as possible, thiss will decrease the percentage error

[vahid_you2004]

Yes, you're right. The longest distance, the more accuracy.

[mdog93]

any chance of a quick viedo of this in action?

[vahid_you2004]

I think it doesn't need any video, rotation of the wheel causes the change in the display number.

[MagicLanternProductions]

Hi nice design. I, need to measure 1,000' + do I, need to use 2, " 1x PIC16F819 microcontroller + socket ? " To add the extra digit, or can I, get by with one
processor unit. What would I, need to make these changes to increase the measuring capacity of your tape measure ?

[vahid_you2004]

Connect the sensor that is connected to A4 to MCLR, now there are 2 free pins on the PIC (A3 & A4) so you can easily add 2 more digits to it, but you must make some changes in the source code.

[rocketman221]

Cool project.
How accurate is it?

[vahid_you2004]

I made this for long distances, It's accuracy is 1 cm or 1 inch.

[-=Dr.Who=-]

Cool project. I love how you used the ink carts as the shell. Bonus for the recycle!
OK, dumb question incoming (sorry, I have to ask it) but, 1 cm or 1 inch...? That's a big discrepancy. If you were talking about 1cm per 1/2 kilometer or 1 inch per 300 yards or something along that line, then it's not that big a deal. But, if it's less than that then I question the accuracy.
Can you be a little more specific about it's accuracy, please?

Thanks!

[vahid_you2004]

Its accuracy depends on the calibration, according to the 7th step you can calibrate it with 50cm line or with a 9m line, of cource calibrating with a 9m line makes the device more accurate. Actually the shortest distance that you can measure with this device is 1cm, when the software converts the result to inches it rounds the number so if you use inch unit the shortest distance is 1".

[Kasm279]

You could also get the IR bits form an old ball mouse! They work exactly the same way actually. You might even be able to use the inside of a scroll wheel for the wheel here. It has the notches in it and everything.

[Kasm279]

Err, scratch the scroll wheel. In the mouse I took apart a while back the wheel had a small rotation sensor (which could perhaps be used instead?) Anyway, ball mice have the wheels with slots in them inside.

[Caspar]

You select the units (cm or inch). Resolution is +- 1 count on the optical wheel. You could use different gearing to get better resolution but the accuracy depends on how well the wheel is in contact with the map (wall, ground ...). Great use of a PIC, I like the way vahid(author) drew the little hands next to the buttons.

[JunkShow]

Actually you could increase your resolution up to 4 times by using Quadrature encoding.
http://zone.ni.com/devzone/cda/tut/p/id/4763
By putting the encoders out of phase by 90 degrees you essentially quadruple the counts per turn. The old mouse should have 2 break beam sensors in it already.

[vahid_you2004]

Very good idea, thanks.

[vahid_you2004]

The little hand mean that you must hold the button, I saw this sign on my refrigrator panel!

[shveet]

by looking at the images, it only measures in inches. no 1/4 or 5/8s i could be mistaken

[snekooei]

good idea.
I'll vote it !!

[vahid_you2004]

If you like this don't forget to vote it at Microcontroller Contest.