Beginner Project

[oexhndan]

Hi All

I'd like to build a very simple digital tape measure. Any help would be great.

Thanks, Dan

[Anson]

You taking laser or traditional with digital readout?

[cthree]

Yes, please tell us more about this project.

[oexhndan]

6/30/2013

Yes a digital readout in ft' in", or if not too hard also able to convert to metric. I live in the US.  What is your opinion between laser or digital readout?

Thank you for your support.

Dan

[Stonent]

Simple is very relative, what you're asking for doesn't really sound all that simple to me.

[duskglow]

That's not to say it's not a worthwhile project and you shouldn't try it - only that there are simpler projects.

[Anson]

It would likely be cheaper to just buy a laser one if your going that route. If you just want to mod/hack a regular 25' tape to have digital readout that would be a fun project. I would think you would need to start with a quality measure, one with very sharp fine lines every 32nd or 64th inch. Then a optical sensor to read each line. An small microcontroller and an lcd small enough to fit the case. For metric you could just add a small momentary switch to tell the mcu to convert inch to metric. Seems easy enough if you can get everything small enough.

They make sonic distance devices for relatively cheap but the accuracy may not be what you would want.

[smashedProton]

May I ask why?  The only reason to add digital to something like this would be to make it simpler to manufacture.  For example digital calipers use a magnetic strip thingy that is easier and cheaper to be graduated than gear ratios.  you add a zero button mcu and lcd and your done.  You dont need to pay someone to muck around filing gears into tolerance.  Adding a digital display to a tape measure would be kind of dumb and a waste of energy because there is no purpose to it.  It would be better for you to make a mains referenced alarm clock or something if you want to learn about digital shit. 

If you are actually a super genius and you are making a laser time of flight digital distance sensor thing, you are the coolest person ever and you should invite me to your lab. 

I hope my comments helped.

[Stonent]

That's not to say it's not a worthwhile project and you shouldn't try it - only that there are simpler projects.

True, if you can get by with a Parallax Ping sensor or the similar Chinese variants that you can buy for a dollar or two, you could easily build a crude distance sensor like I did using an Arduino, but if you throw in a laser, it may add to the complexity quite a bit.

[Anson]

May I ask why?  The only reason to add digital to something like this would be to make it simpler to manufacture.  For example digital calipers use a magnetic strip thingy that is easier and cheaper to be graduated than gear ratios.  you add a zero button mcu and lcd and your done.  You dont need to pay someone to muck around filing gears into tolerance.  Adding a digital display to a tape measure would be kind of dumb and a waste of energy because there is no purpose to it.  It would be better for you to make a mains referenced alarm clock or something if you want to learn about digital shit. 

Maybe he is a poor sighted woodworker and wants an easier way to read his tape. As someone who uses a tape measure often I can see the benefit and the coolness. Just because you don't is no reason to be rude.

[penfold]

Now, what would be quite useful is a hand-held trundle wheel type, something 3" or 4" in diameter. An endless tape measure!
So it would be a disk with encoder marks on and a microcontroller to count the encoder marks and keep track of distance traveled.

Next, i'm sure somebody is going to moan about the fact you'd have to keep the thing moving in a straight line to stay accurate, which you would, but there you can eventually add a second wheel and do some clever maths to work out deviation from straight. Or even store details of the line traced that can be loaded to a computer