Like [Brad], we’ve seen a number of PCB rulers out there. [Brad] was looking to take the idea and run with it. His DigiRule is a ruler with a logic gate simulator. What he built is a mash-up between PCB rulers, and the concept of electronic business cards.
All told it simulates seven logic gates, four flip-flops, and includes a four-bit counter. On one end of the ruler a CR1220 battery feeds the 18F43K20 which is performing the logic operations using buttons and LEDs. Of course the truth tables are printed on the back silk-screen, but playing with the lights is a lot more fun. We do find it fairly amusing that the centimeters on the bottom of the ruler are notated in binary.
It makes a lot more sense to hand out rulers than business cards; people might actually use them after you leave and you can still include contact info. This form-factor also breaks the mold. You can have a lot more space on a ruler and you’re not constrained by thickness (although [Limpkin] solved that problem). While we’re on the topic of business cards [ch00f’s] USB etch-a-sketch style card and this logic-based information delivery device top our favorites list.
[via Dangerous Prototypes]
Looks really good. It would be great for beginners / students.
The only thing that I would *try* to do differently would be to recess the the cell into the board and use a CR2016 or LIR2016 and perhaps a USB plug printed on the board for recharging.
I don’t think you will have the ruler on often enough to really warrant a charging system. The recessed thing would have been neat though.
Would be better if the rulers’ 0 were 0mm away from the edge.
Subject to errors/tolerances from manufacturing the PCB or damage from normal use. The way it is designed is the best method.
Ehh, The backside is pretty well on the edges, but I was thinking if an extra step isn’t minded it could be shaved/sanded down post-production
Use the linear optical sensor from a flat bed scanner. Let it find lines on your paper and give the read out of how many pixels away they are from each other.
I want to see someone build a digital slide rule using parts from high resolution digital calipers.
Go for it, I’ll enjoy reading the HaD article about it :-)
+1
Hilarious the SI units are measured in binary since it is fundamentally a decimal system. Conventional Measure, OTOH is often binary or at least partially so. (1/2, 1/4, /18, 1/16…) (cups, pints, quarts, gallons, etc.)
Yeah, and aren’t they oh so consistent when you have to convert one to another?
There doesn’t seem to be any switch debouncing in that code
There doesn’t appear to be any switch debouncing in the code.
When he sets the flip flop to JK mode and both J and K as ‘1’ (equivalent to toggle) the toggle only occurs once per button press so there must be some de-bounce somewhere. Perhaps he is scanning the button slow enough that bounce isn’t an issue.
I think the switches that he uses don’t have much debounce
there’s something ironic about a double post talking about debouncing, isn’t there?
there’s something ironic about a double post talking about debouncing, isn’t there?
Interesting. ~F
A microcontroller for this? Seriously?! My head weeps.
One chip to solder v. one for each section? Yes, it could use a GAL/PAL/etc.
Agreed. I think this is cheaper that discrete chips or PAL/GAL/CPLD.
Not only was the CM scale in binary, so was the Inches…. I a Metric user and still noticed it. Come on HaD!
A kickstarter was just opened for this and it’s filling up fast –
https://www.kickstarter.com/projects/1897710270/digirule-the-interactive-binary-ruler
This bloke seems to have done a couple of kickstarters before so he has my confidence but you will have to make your own judgement.