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Mercredi, 26 septembre 2007

Power Consumption of a Yepp MT6Z

Traduction: [ Google | Babelfish ]

Catégories : [ Science ]

Yepp_MT6

Thanks to Niko's help, I managed to measure the current drawn by the Yepp while playing an MP3. The trick was to use a voltage source set to 1.2 V, and then read the current from the power supply's display. The first method I tried, using a simple amperemeter, doesn't work, unless the meter is set to measure 10 A currents. According to Niko, this reduces the amperemeter's internal resistance and minimizes the voltage drop it provokes, allowing the Yepp to get enough power to boot, but it also reduced the precision of the measurement to 10 mA steps. Here are the measurements:

  • 60 mA with no headphones or volume set to 0.
  • Between 60 and 70 mA with 13 Ω impedance headphones and volume to maximum.
  • 20 mA when paused.
  • slightly over 100 mA with the LCD backlight on.

From these values, one can easily calculate that while running, the Yepp consumes about 72-84 mW, and only 24 mW while paused. Moreover, with a 2500 mAh NiMH battery, it should run 35 hours.

However, NiMH batteries have a high self-discharge rate of 5-10% the first day and 0.5-1% the following days, so my 2300 mAh battery used over approximately 6 weeks (charge it, store it charged for 3 weeks, then use it to replace the old battery and use it for 3 weeks) has an actual capacity equivalent to 1400 – 1800 mAh, which in turn should give about 20 – 25 hours or usage.

[ Posté le 26 septembre 2007 à 23:40 | pas de commentaire | ]

Dimanche, 23 septembre 2007

Fujian Oolong (Sea Dyke Brand)

Catégories : [ Thé ]

Fujian_Oolong_box

Je suis passé au magasin asiatique dans la galerie marchande du Citymarket de Seppälä, et par curiosité je suis allé voir les thés qu'ils vendent. J'ai hésité à prendre un pu erh en vrac, jusqu'à ce que je me rende compte qu'il provenait de l'Anhui, ce qui n'est pas vraiment la région d'origine du pu erh. En revanche, j'ai acheté un wu long du Fujian. J'aurais pas dû.

Fujian_Oolong_leaves

Il est très fortement torréfié, en fait beaucoup trop. J'ai l'impression de boire une infusion de pain grillé beaucoup trop grillé tellement le goût de quasiment brûlé occulte tout le reste. On distingue un goût légèrement sucré, et absolument rien d'autre. Enfin bon, à 3,20 EUR la boite de 125 g, on a ce qu'on a payé.

[ Posté le 23 septembre 2007 à 14:17 | 2 commentaires | ]

Dimanche, 2 septembre 2007

Polyurethane Foam

Traduction: [ Google | Babelfish ]

Catégories : [ Bricolage ]

Polyurethane_foam_mushroom

I tried to make a block (12x12 cm) of polyurethane foam with a cardboard shape, but what I got was this mushroom full of air and wet on the inside. Moreover, it leaked during the night, so some amount of the PU inside came out, increasing the size of the inner cavity. I'll let it dry a bit before throwing it away, but I'll have to find another way to make my blocks of foam. Maybe making a 6x6 shape out of wook? Note to self: don't fill the shape up to the rim, the foam expands about twofold. Less foam would dry quicklier.

[ Posté le 2 septembre 2007 à 09:23 | 3 commentaires | ]

Samedi, 1er septembre 2007

Dice Tower, Part 1

Traduction: [ Google | Babelfish ]

Catégories : [ Bricolage | Jeux ]

Dice_tower_3D_plan

I've decided to build a dice tower. Not the same as everybody else is building (not that it's not good, I'm just being posh there), but a tower where the dice roll in every direction, instead of in only one vertical plan. Drawing the plan took two evenings and a bit of a headache for the middle part, but it's done and the plan looks correct. The core is going to be 36cm tall with a 12x12cm base.

For the building, I've decided to carve it out of polyurethane foam. I've bought a can of liquid PU foam, and I'll have to make three cubes out of it. I'll use a cardboard box as a form, and carve the cubes with saw and knife. The I'll glue the cubes together and add side walls and a tray at the bottom for the dice to roll into when coming out of the tower.

[ Posté le 1er septembre 2007 à 17:10 | 4 commentaires | ]