Not too bright guitar tuners (Snark)

[Renate]

It's become the standard clip-on guitar tuner, the Snark (and its variant, the Super Snark).
You put in a fresh coin lithium battery (CR2032) and it looks nice.
By the time you've used up 5% of the battery you're shading the display with your hand and squinting to see.

Without thinking I presumed that this thing was LED. No, it's LCD with a white backlight and a colored filter.
The LCD is fed on a standard "zebra" piece of rubber. The chip resides under a glop on the PCB.

I tried replacing the tiny chip LED that feeds the backlight with a chip LED I got off a dollar store flashlight.
It helped a bit, but not enough.

I was original thinking of just attaching a triple AAA holder and feeding it 4.5 V instead of 3 V and seeing how it liked it.
The backlight anode goes to BAT+ and the cathode is pulled through a 10 ohm to ground by the chip.
It is PWM'ed. I've seen both 50% and 25% duty cycles and I have no ideas what makes it switch between the two.

I happened to have a little Velleman VMA321 LiPo charger and a random Lipo.
You can actually solder glob the VMA321 onto two points of the Snark PCB that nicely take the power.
The angle and position of the VMA321 is good enough that you don't even need to trim the Snark case.
It simply exits where the battery cover was.

Is it ugly? Oh, yeah.
It's just that I'm not going to buy caseloads of CR2032 just to use 5% of their capacity.

[SilverSolder]

Cool mod!

Maybe I just like dark, smoky rooms...  but I've never had problems seeing the display.

[bob91343]

Break down and buy a new one.  There are many options out there, including apps for your cellphone.  They cost as little as a dollar or two.

[Renate]

Maybe I just like dark, smoky rooms...

Well, try playing at noon in the desert with a pure blue sky.
Even without direct sunlight those things are hard to read.

I play acoustic solo, acoustic with other people, amplified solo and amplified with other people.
A clip-on is the simplest solution.

I was just hoping that since the deficiencies of Snarks are pretty well known that somebody would have specific knowledge of something better.

In the final analysis I a) identified a problem that annoyed me, b) solved it with parts on hand.

Oh, excuse me, Snark Inc is calling to discuss the royalties on my invention. They really liked the Ty-Wrap bit.

[james_s]

Maybe replace the LED with a brighter one? There are some freakishly efficient LEDs out there these days. I recently had to replace the 100 ohm resistors on a dev board with 3.3k resistors because as received the 0603 sized green LEDs were painfully bright.

[Wimberleytech]

I have three or four Snarks.  Prolly at least five years old.  Never had this particular problem.

On one of them, the swivel mount broke.  Found a solution on Thingiverse and printed the fix.

I recently bough another tiny tuner for my ukuleles.  This oneÑ  D'Addario Micro Guitar Tuner, Headstock Clip-On

Its OK.  Still like the Snarks

[mikerj]

A 3V lithium coin cell feeding a white LED is always going to be problematic, the Vf of the LED is likely only a little under the fresh battery voltage so a small drop in voltage will greatly reduce light output.  Replacing the white LED with another colour that has lower Vf (e.g. yellow or  red) might be a possible solution.  OTOH you might be able to kludge a tiny boost converter into the unit to raise the LED anode voltage a little.

[CaptDon]

MikerJ, you are very correct about the VF of the white LED.
Some of the first white LED's on the market wouldn't hardly
light from a TTL driver even with a pullup!! Their specs were
something like VF=4.2v  Some of the lighted fishing bobbers
put the LED directly on the battery with no resistor!!! Talk about
brutal!! One or more of the ultra high intensity green LED's would
probably work well and be readable in sunlight. I use a Korg DT-1
handheld tuner and let the other musicians borrow it during the gig
and I have a rack mount DT-2 in-line feeding my effects rack. The
hand held can be hard to see in direct sunlight, I think the rack unit
has polarized light filters in front of the LED's as it is very easy to see.

[james_s]

Lots of lighted things connect the LED directly to a CR2032 coin cell and rely on the internal resistance of the battery. It's not a great design but it does work reasonably well.

[rvalente]

When I was a kiddo, about 6...7 or so was in to electronics because of my dad.
I had a chinese clone of tamagochi and that ate a pair of LR44 in a week or so I soldered a pair of AAs and some electrical tape did the job haahha

[bson]

A small 3.3V boost converter should take care of it.

http://www.rockgarden.net/download/eevblog/bat33.png

Put a CR2032 coin cell holder on one side and the converter on the other.  The PCB will be the same size as the coin cell holder.

[emece67]

.

[BrianHG]

Disconnect the LED and rotate/flip the LCD polarizer so you get a negative image, IE the display will look like a normal calculator.  The active segments will appear black and everything else will become transparent.

You'll also save on the battery when you do not need to power a LED from a lithium coin cell.

[Renate]

I remember having used the same "technique" to power a Texas Intrument LED wristwatch...

Ah, that brings me back to the good old days of the HP 35 calculator.
(With the "Easter egg" of timer mode that they punted because they decided for RC over XTAL.)

[Wimberleytech]

I remember having used the same "technique" to power a Texas Intrument LED wristwatch...

Ah, that brings me back to the good old days of the HP 35 calculator.
(With the "Easter egg" of timer mode that they punted because they decided for RC over XTAL.)

Worked on HP45 as well.

[Renate]

So, Snark, Chapter II

The Snarks have a little 10 mm piezo sensor glued to the back of the case. They use two springs on the PCB to connect to it. It's a well-known problem that the contacts on the piezo corrode and fail to make contact. The usual solution is a good wack on a hard surface. Mine was failing to work properly so I took it apart. The top plating was almost black. I used a Q tip in a Dremel tool with toothpaste and it did a perfect job of polishing it up without doing any damage. I decided to try to solder wires to it to replace the brushes. The big brass disk that is the base was no problem. The top coating was. When I got my soldering iron near it the top coating disappeared like morning dew. Fortunately I had a bigger piezo disk on hand (with leads pre-soldered). I Dremeled out a bit of the case and epoxied it in. Although it hasn't dried yet I can see that it works fine and will be pretty sensitive. I have it clamped to my monitor so that it can dry in position and I can sing at it just fine!