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bluehash

[Group Buy-19][O] TMS0803/5 Emulating Calculator With Bubble Display

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Yes! 87 replies to this topic has changed :D

 

and, yes please, could you solder *ONE* of my TWO up please (hedge me bets!)

Touched a soldering iron recently but burnt the case of the thing I was soldering; also it has a big fat tip so I'd probably need to invest in a new thin one

 

I'll keep the unsoldered one to show how it's done! :P

 

PM me the PayPal details please

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Yes! 87 replies to this topic has changed :D

 

and, yes please, could you solder *ONE* of my TWO up please (hedge me bets!)

 

Touched a soldering iron recently but burnt the case of the thing I was soldering; also it has a big fat tip so I'd probably need to invest in a new thin one

 

I'll keep the unsoldered one to show how it's done! :P

 

PM me the PayPal details please

Yes.. I can do that for you. I'll PM you the address.

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A quick question for @@simpleavr ... I was reading through some of the early comments about "evening out" the current to the LEDs and I was wondering if there are any combinations (e.g. just two segments in a single digit 1) which, left glowing, would burn out the segments of the LED or is this issue solved now?


I don't mind if it is ... I would just make a note to myself to not leave it burning away like this and on similar such segment combinations

 

@@bluehash suggested that we could program an auto-off on the LEDs, if there was no button input for a certain amount of time... or even goto low power mode; I'm guessing these solutions, if needed, would be simple re-flashes of the software?

 

Thanks :)


 

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@@PhilM

 

The way I am direct driving the LED is not the "correct" way to drive LEDs and could reduce the lifespan of LEDs. The proper way would be to drive them via transistors and current limiting resistors. Which in this project (or most of my projects) I decided to skip them to keep the component count down and to save PCB space. To me it is more important to get this on a easier to build thru-hole layout.

 

LEDs can allow excessive current on a very brief period and since we are doing multiplexing already, we are not constantly turning on each individual LED at the same time. I think of it as a PWM (pulse width modulation) way to limit current.

 

This link had a good discussion on it.

 

http://tinkerlog.com/2009/04/05/driving-an-led-with-or-without-a-resistor/

 

It does have its drawbacks, depending on what is displaying, there are voltage drops to the whole circuit. Fortunately this project is all digital and the voltage drop does not affect the functioning.

 

When we do multiplexing, we turn on the 8 digits one by one. And for each digit's on time, it needs to sink (or source) 8 segments at the same time. Ex. when we display "1", we are driving 2 led segments, and when we display "8" we are driving 7 segments, which has a bigger voltage drop and is less bright.

 

When I mean of "evening out" is that during multiplexing, we alter the time to keep a particular digit on (or off) based on the number of segments it need to drive. I.e. say when we display "1", the digit stays on for 10us, and for displaying "8", the digit is made to stay on for 25us, etc. This will result in a more consistent brightness regarding of the numbers it is displaying.

 

I won't worry about damaging the LEDs. Been driving LEDs like that for many years. I've built 6 of these and I use one regularly every day. They are just not bright enough for under-the-sun use as there is no driver.

 

As for @@amstan LED donation, which I mentioned in an earlier post that I managed to blow one of them, it turned out that (I believe) it was bad before I tried them. I finally got time to check all the 80 LED modules and it turned out most has some problems. There are 23 units that are good, the rest all have either missing digits or segments. And some of them has one or two "weak" segments, etc. I recall buying from ebay that had similar problem. Guess this is what happen when they sat in a bag for 20+ years.

 

Anyway I am still working w/ blue# on the group built units and hope they will be ready really soon for you.

 

 

 

 

 

 

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Did a quick case - slides on like @@simpleavr suggested.  https://tinkercad.com/things/cDc15bMgwAt-calculator-cover/  

Trying that out to start - but I'll probably also do a bumper + case to protect the user from the bottom of the circuit board.  Should have my PCB in a couple of days.

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@@sq7bti has the old style 9 digit led modules and built on the "version 0" board.

 

That was the original design I started out w/ but I did not get the led part. Works out quite nice. But now I prefer the version 2 boards, I guess the tilted Sparkfun LEDs works better for the small size layout.

 

The version 0 board has it's own beauty, it got the exact 9th digit, is longer and looks slim. I would try to use some transparent file separator cut-off the filter the bubble lens though.

 

post-23-0-18955700-1411133287_thumb.jpg

 

post-23-0-12543700-1411133321_thumb.jpg

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All good! Wrong tongue angle.

 

Love the programmable easter egg! Well done.

 

Still got a lot of room (unused flash space) to roll your own variations / functions. Just have to bear w/ my messy code and build on top.

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Got my two. Chips no flashed? I must have mis-read that they were flashed...

Is there an Energia sketch, or am I forever destined to be the dumb kid eating paste in the corner?

Hmm... I did program all chips except for cubergs and greeeg

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