Better, Smaller WiFi Throwies

Because the world doesn’t have enough electronic junk floating around, [Victor] has improved the WiFi Throwie.

A decade ago, when strong, cheap magnets, bright LEDs, and small coin cell batteries were materials fresh to hacking, someone had a great idea: tape all these items up and throw them on bridges and overpasses. The LED throwie was born, and while we’re sure the biggest installation of LED throwies looked cool, it’s really just a small-scale environmental disaster.

Since then, the ESP8266 was created, and the world now has a tiny WiFi-enabled computer that’s the size of a postage stamp. Yes, WiFi throwies already exist, but coin cells don’t work with the ESP. This means the compact and tiny ESPs are laden down with heavy lithium cells. [Victor] had a better solution: tiny lithium batteries for quadcopters exist, so why not use those?

[Victor] ended up using a small 100mAh 3.7V Lipo battery from a tiny quadcopter for this build. 100mAh isn’t a lot, but in sleep mode, the ESP only uses about 15mAh, or about 6 hours of run time. Sending a picture takes 30 seconds at 120ma, or about 120mAh, so even with a tiny battery no bigger than the ESP itself, this diminutive web server can handle 100 connections before the battery dies.

While not recommended unless you intend to retrieve your throwable web server, it is an interesting example of the latest and cheapest technology that made a throwable webserver possible; 10 years ago, both the ESP and a battery this small would have been unthinkable.

47 thoughts on “Better, Smaller WiFi Throwies

        1. You would need a 360F capacitor. Which is very bulky and expensive. I even doubt that an electrolytic capacitor (supercap/goldcap is electrolytic) the size of a brick is more environmentally friendly than this tiny LiPo battery.

      1. Got something like this instantly after first seeing one in person. The solar panel doesn’t appear to ever charge the battery in any meaningful way the battery itself is dead-ish inside of two years, and any overcurrent on the output caused it to shut down in such a way that it could not be recovered without supplying 5V to the input jack. It’s also not waterproof.

        On the plus side, the one I have did include a wide array of DC power plugs and switchable output voltage (up to 12V), and would charge from 5V and output whatever selected voltage concurrently,so the concept does have some potential for being a small and cheap DC-DC UPS for small loads like a low-end router or (some) broadband modems. Or maybe as a quick boost converter for hacking.

        It languishes in a drawer somewhere, however, because I’ve quickly forgotten just how useful battery-powered bandwidth was since the last time my house was without power for over a week.

  1. The arrival of throwies was when I first realized ‘my hobby’ was growing quickly.. “But how can these people just litter like this? they would never normally litter!” I asked my friend who had asked me to help her build some throwies.


  2. If you tie the wakup gpio to the internal alarm pin you can reduce the sleep current to 2ma. The chip boots itself. You can also patch the config blob to decrease the WiFi start current by 30%. I’ll paste links when I get on my pc.

    1. The coin cells still dont have the power and the boost converter drains the battery even with the esp in sleep mode.
      If you use a battery at the right voltage without the need for the converter you dont have the constant excess drain from the converter.

      Loads of conersations on this on the forum and how to get the most out of battery power.

  3. “in sleep mode, the ESP only uses about 15mAh,”
    “Sending a picture takes 30 seconds at 120ma, or about 120mAh”

    I’m not one to complain about minor typos or incorrect word usage, but getting units wrong like that? I refuse to stay silent! I”m as mad as hell, and, I, uh, what was I saying?

    1. i do not understand your math,
      30 sec at 120ma will cost you 1mAh, not 120
      so you can send 500 picture from a 500mAh battery.
      And from the same battery, without picture you can stay in sleep for 33h

      1. I am guessing you are looking at the wrong numbers. the CC is better, but not even by a factor of 2. Example: it needs 59mA in RX vs 80 for ESP.
        On the low power side, the ESP would need 1.2mA with DTIM 1, vs 0.8 for CC. However i did not see many ESPs being made to operate in sleep mode with DTIM wake up yet.
        There are however other areas where the ESP kind of sucks….like waking up from any pin requires a sleep current of 0.6mA…really bad. Still, it is a more attractive chip than the CC because of price….which also build a much bigger community around it.

    2. This is exactly why I stopped reading Slashdot- it called itself “news for nerds” and made basic errors with dimension when talking about energy production which made their article summaries meaningless. It’s clear whoever wrote this either
      a) was in a massive hurry and had to type faster than they could think
      b) has no idea what mA and mAh means and just decided to sprinkle a few throughout the summary, like IP addresses in Hollywood hacking, to make it look better.

  4. Use a solar cell and NiCad batteries. LiPo’s need very special charging while you can abuse the hell out of NiCad/NiMh batteries for a long time with a direct solar cell charging before they die.

    Yes it makes it bigger, but it also makes it last dramatically longer, possibly an entire summer

    1. Easier way to do this is to hack a 4$ smartphone solar powerbank – includes case (with enough space for the ESP), battery, solar panel & power control. You only need either a cheap 5V to 3.3 V converter, or to hack the power management module to get 3.7V output (which is what the battery delivers) instead of 5V. Anybody knowing how to do this ?

        1. Or just gut the dollar store garden lights, epoxy a sufficiently-big magnet to those guts, and have a go at it the old fashioned way.

          Solar-powered thowie, $5.

          (OI course, these cheap lights only last for a few months, and even when in their prime only produce useful light for a couple of hours after sunset.)

          1. I have been getting rather good results using the 97 cent ($.97) lawn lights from WalMart. They are out in full sunlight mostly, with a few in partial shade. I leave the house for work at 4:15 am and most if not all of the full-light ones are still it, the shade ones are out. We have ~75 of them out on the lawn, and the only fatalities after a year is due to water rising. :( The clear plastic lens does fog with age, and not give the same pattern or brightness as new. But hey, for less than a $1.. good show.

            image –

            I have also gutted the lights and used the circuitry for small party lamps. Worked well!

    2. Please don’t use NiCads unless you will be picking the device up and recycling it. Scattering batteries around the landscape is never a good idea, but at least NiMh and LiPo don’t add cadmium to the environment.

  5. Just to keep the information honest: the esp modules use about 30uA (microAmp, not milliAmp) in deep sleep. The latest ones (e.g.esp-12e or -12f) go as low as 10uA. deep sleep is what you will normally do most of the time, then one in a while wake up and do something, using on average 80mA (if WiFi is on, much less otherwise) so spending a few 100s mAsec. Forget other sleep modes when running on battery power.

      1. I have one, identically looking, from a store in vienna. It has 3*40mAh NiMH cells in it and it did charge them until I dropped it from 10 or 20m of height. I found all parts and put it together again and wondered 2 weeks later why it is empty. The connection from the 1N4148 diode to the glass solar cell was broken. Luckily there was a second connection point on the glass, so I could repair it.
        I would like to (and think about) replacing the Batteries with a small 200-300mAh LiPo. But for this I need an ultra-low quiescent current charge regulator.

      2. I bought one from eBay, looks exactly like that. Solar panel is not connected at all, but it is a solar panel, if you solder wires to it you can measure voltage and current when exposed to light. LEDs were conected to coin cell, not rechargeable one. There are bunch of fakes like that on eBay, they last just enough to give positive feedback, then they die.

  6. Since the maximum voltage spec on the ESP8266 is 3.6 volts and LiPos put out 3.7V (4.2V fully charged) it would seem the life expectancy of the chip with this battery connected directly to the ESP-01 shown would not be long.

    ESP8266 boards with regulators on them usually need close 5V input to generate 3.3V for the chip.

    1. LDO (Low Drop Out) that uses CMOS/DMOS are what you want as they usually have 100-300mV drop out in full load and low quiescent current in the uA range.
      The old transistor based one such as the cheap/popular 1117 ones have 1.1-1.3V drop typ and 5-11mA quiescent current and are not suitable for long battery life.

  7. “in sleep mode, the ESP only uses about 15mAh,”
    “Sending a picture takes 30 seconds at 120ma, or about 120mAh”
    Congratulations Hackaday on joining the ranks of “tech” blogs posting meaningless gibberish about energy/power using the wrong quantities, units and time dimension. Silly grammar mistakes are forgivable; complete lack of understanding of the difference between energy and power in an article summary *explicitly about battery capacity* is not.

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