Blinkring

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Blinkring

Postby Bertho » Fri Jul 19, 2013 1:38 pm

Hi all,

An idea of a blinking earring was born while talking at the local hackerspace. Inger was playing with harddisk parts and wanted to make blinking earrings. She has been doing workshops making jewelry from old computer parts (very, very nice; she is not an engineer/technician).

Well, we were discussing a more advanced version and this is what I came up with and how it looks (31mm outer diameter):
blinkring-assembled-front-small.jpg
blinkring-assembled-back-small.jpg


The paperclip trick was inspired from matseng's idea (many thanks!) and it uses a standard cr2032 battery.
blinkring-active-front-small.jpg


Hanging on my ear blinking:
blinkring-earring-dark-small.jpg


There are still some issues with the software and the documentation is of yet non-existent. These issues will be addressed and published on my homepage when I have it working.

I plan to sell these on Tindie soon. The first batch (30 or 35) will be available at OHM 2013 (which I will attend, http://ohm2013.org) if I get it all to work.
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Re: Blinkring

Postby matseng » Fri Jul 19, 2013 11:15 pm

Nice! And when I saw the first image i thought "Hm... That battery holder looks familiar." :-)

What's the wire loop at the backside for?

Unless you've already done this (which you probably already have) Connect the loop to the reset pin pulled up by a 3M3 resistor. Then set the fuses so Reset becomes a GPIO and have a interrupt-on-change on it. You can then use it to wake the ring up by squeezing your fingers between the loop and gnd.
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Re: Blinkring

Postby Bertho » Sat Jul 20, 2013 3:25 am

matseng wrote:Nice! And when I saw the first image i thought "Hm... That battery holder looks familiar." :-)

Yes, you had a great idea which I could not resist of re-using ;-)

matseng wrote:What's the wire loop at the backside for?

That is a switch.
blinkring-switch-detail-small.jpg
Switch closeup

The current form is not very nice, it needs a winding at the long end for flexibility. The second version will include a "real" switch on the back of 2.4x3.4mm because it is simply too much work to make the switch and align it correctly while soldering. This first batch of PCBs will be unique; a collector's item in 100 years ;-).

matseng wrote:Unless you've already done this (which you probably already have) Connect the loop to the reset pin pulled up by a 3M3 resistor. Then set the fuses so Reset becomes a GPIO and have a interrupt-on-change on it. You can then use it to wake the ring up by squeezing your fingers between the loop and gnd.

The reset is not used and has an internal pull-up (about 40k). The switch is connected to an available GPIO pin. I had considered doing a high impedance pull-up and let the finger make the connection, but that required that one extra resistor that would break symmetry on the front (yes, I know, vanity has a price). I now use the internal pull-up of the PIC12LF1552 to keep the pin high.
blinkring_1-small.png
schematic diagram

The first version of software is now running and multiple patterns can be displayed. I managed to squeeze 16 level PWM in a 12 LED charliplex while running at Fosc/4=250kHz. Pressing the switch changes between 20 or so patterns, while holding it for 2 seconds turns it off (and it will then sleep).

The LEDs are two-in-a-house red/green ones. I thought that they would be about same brightness, but it turns out that the green one is significantly more dim. The charliplex loop-delay is slightly altered, showing green longer than red, to compensate for the difference. I will see if I can get dual LEDs which are a bit brighter so the visibility in sunny daylight improves, but it is not strictly necessary.
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Re: Blinkring

Postby matseng » Sat Jul 20, 2013 3:42 am

That's cool, with 4 bit pwm as well!

I only counted 6 leds from the prictures and assumed you were using a PIC10F-series device - there you have to use mclr for the switch if you want 6 charlieplexed leds. You went a bit up the scale and used a proper device. :)

Well, you could still use the resistive finger touch method on RA2 (or RA3/mclr as well if you configure it for gpio without internal pullup) if you like. But a real button is probably the best.
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Re: Blinkring

Postby Bertho » Sat Jul 20, 2013 4:35 am

matseng wrote:That's cool, with 4 bit pwm as well!

I was feeling lucky ;-)

matseng wrote:I only counted 6 leds from the prictures and assumed you were using a PIC10F-series device - there you have to use mclr for the switch if you want 6 charlieplexed leds. You went a bit up the scale and used a proper device. :)

Yes, a proper device. Except that I couldn't program it at first. I had to hack my pickit2 dat-file to include the 12lf1552 (microchip is too slow with updates). The controller criterion was low-power. Initially I had only 6 LEDs, but I found the dual version while browsing for components and decided it would be "nice" to have more. It always seems nice to have more... That caused me to compromise on intensity because red/green as single LEDs are available in significantly better brightness than dual ones. However, the dual version makes an indication of yellow when both are on.

matseng wrote:Well, you could still use the resistive finger touch method on RA2 (or RA3/mclr as well if you configure it for gpio without internal pullup) if you like. But a real button is probably the best.

I'll settle for a real switch. The finger method is not entirely fool-proof and the hand-crafted switch is too much work. The battery-holder will be rotated 90 degrees when I put in the real switch to get symmetry again on the front-side. Also, I intend to make a loop/winding at the base of the battery-holder's front-connection to have a better spring-action. Some experimenting is still in order I guess.
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Re: Blinkring

Postby Bertho » Sat Jul 20, 2013 2:53 pm

I updated both the switch and the battery-holder's plus contact:

blinkring-new-switch-detail-small.jpg
The loop/winding ensures a better spring function and makes it a lot easier to press the switch. The folded part makes it easier for the finger to press down and the contact below it is easily hit. It is still a lot ow work to make though.

blinkring-new-batholder-small.jpg
Also the battery-holder has a bit more spring function now. The leads of the paperclip were not long enough to create a full loop, so I settled for a bit of bending. It is a lot better now than without the bends. It also makes it easier to adjust the height of the paperclip to have a good fit and force balance.
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Re: Blinkring

Postby Bertho » Mon Jul 22, 2013 8:53 am

I updated my homepage with the design at http://www.vagrearg.org/content/blinkring. There are links to the schematic diagram, the running firmware and a small video with some blinking action.
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Re: Blinkring

Postby Bertho » Wed Aug 07, 2013 4:10 am

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