Making things on a beach: bamboo tongs

Instead of solving sudokus, why not making something useful for the environment?

Did you ever go to a beach so far away from everything else, so isolated, so hard to access, to find out it is littered anyway? That’s not unexpected: isolated places are gorgeous, but they have nobody that looks after them. Do you remember when #TrashTag was trendy? I might be a couple of years late but I decided to took the matter in my own hands anyway or at least do my part of picking up some bags of trash.

The bamboo tongs are very effective at picking up trash from the sand (also for relocating the occasional jellyfish, if needed). You’ll find out that if you can see trash on the sand surface, it means there will be (a ton of) more trash below. Bamboo is pretty common on the seaside, it’s sturdy, and the tongs are long enough to make me feel safe whatever I pick up.

Making the tongs is simple, but here is a step-by-step guide anyway. Be careful with sharp tools.
Find a bamboo stick with at least 2 uncracked sections, ideally around 2cm thick, at least 20cm long.
Cut it sideways so that you keep a “knot” about 2cm from the tip.

If your Swiss army knife has a reamer, it’s a good time to use it as a drill tip to make a hole. Do it about 2cm from the knot, on both sides of the bamboo.

Then with a knife make a cut at the side of the hole, pointing down the long end. The round hole will prevent the crack from going upwards.

You’ll end up with a chopstick-like bamboo strip, that you can discard.

Starting from the round hole again, cut diagonally. Try to cut in a straight line. Don’t overdo it and don’t rush it. Don’t cut the bottom away. Make several incremental passes. The bottom end of the tong should be almost flat.

Pinch the tong to check it is straight. Flatten the contact points so that the whole border touches each other.

That’s it. Don’t forget to bring a small bag with you; the best places to go don’t have trash bins, so a bag is always handy to clean after yourself, and with a simple tool you can also leave the place a little better than how you found it.

The laws of cooking as Venn diagrams

I’ve been reading Justin Warner’s excellent cooking book The laws of cooking: and how to break them.
I tried to make an extreme summary of the laws, and represent them as Venn diagrams, where each set in the diagram is a set of flavours that work well together according to the book. Do not worry, it’s not a spoiler: the book is still very worth buying.

I was expecting something more complicated to show up: only 3 flavours belong to more than one set (if we don’t count “Salty”, which goes well with everything). And this is including a slight personal “update” to the laws that I made, by splitting the “sour” flavour in two different flavours: “sweet” and “acid”.
Also, for those of you that try to avoid fat foods, I have bad news.

2€ charger for any kind of lithium-ion battery

Lithium-ion batteries are everywhere and they are awesome also for hobbyist projects. I’ve been tempted more than once to use old smartphone batteries in my projects, but recharging them might be a problem.

Well, this time I tried my hand at recharging small coin-cells like the LiR2032. I’ve been looking around for commercial chargers, but they seem to be kind of unpopular. Turns out you can do one yourself with less than 2€.wpid-wp-1448223544369.jpeg

The TP4056 (datasheet here) is a little IC which serves the purpose perfectly and currently it can be found on along with an additional protection circuit for 1.57€. However, this version comes pre-packaged to work with bigger batteries (>1000 mAh) and shouldn’t be used with coin-cells. Lets see why.

The difference lies basically in the charger’s maximum charging current. The previously linked TP4056 uses 1A maximum current, but LiR2032 datasheet recommends a maximum of 35mA. This current is regulated by a resistor placed between pin2 and ground on the charger (which on this board is called R1 and has a value of 1.2kohms). So, looking at the datasheet and doing the maths it turns out a resistance of about 35kohm is needed.


Okay. let’s go. I used

  • the TP4056 board,
  • a coin cell battery holder,
  • a 47Kohm resistor
  • a 10cm ribbon
  • some pin headers, wire, PCB and soldering

The assembling is quite straightforward, I just cut the PCB to size, mounted the TP4056 board on male pin headers, and mounted the coin cell holder over the ribbon, which I added for easier removal of the battery.

I didn’t have a 35Kohm SMD resistor available, so I replaced the old one with a “regular” 47Kohm resistor. Charging will be slower, but basically the slower the better. Soldering was doable although not trivial, a good set of pliers and tweezers definitely did help.


I soldered the wiring on the back… double check for correct polarity.


And voila. Charging an almost completely drained out battery took about 3 hours, during which all the assembly stayed at room temperature (based on a very accurate measurement with my fingers). Green light means charging done.


I still have to figure out exactly how to use this thing with bigger batteries, the main issue being find a way to keep the battery still. This is probably not going to be trivial since Li-ion batteries tend to come in every shape and size. Maybe I could use cable ties or rubber bands… I’m taking suggestions!