Or you could just wire it up to a microcontroller and busy-loop ADC-convert the input. Staying in the analog world alone, you can output the voltage into a 555 Timer, and then have it flash an LED every time the capacitor filled up (and the discharge would also dump the capacitor). I'd recommend you do a 9V project with the LM358.Īn integrator should be in the circuit "somewhere", but there's a lot of creativity available where I left off. Its good to learn how to use OpAmps, and learn all the issues (ex: Rail to Rail, positive / negative voltages, etc. Voltage-multipliers though are a trivially easy OpAmp circuit, and I'd recommend that beginners actually try to build their own current-sense amplifiers from scratch. (so 0.0001V into the amplifier comes out as 0.02V), and 0.02V can be measured by pretty much anything. They just multiply the voltage by 200 accurately. So trivial, that people sell cheap chips that already do this for you, called current-sensing amplifiers. Now the question is "how do I measure 0.0001V accurately" ? And that's a trivial op-amp problem. Analog wise, its very simple: a small 0.01 ohm resistor (called a "current sense resistor") is placed in series, and you measure the voltage drop across it. If you're off of battery power or USB power instead, you'll need to build a current-sense circuit. Obviously, it depends on your power supply, but even a $50 one these days has this feature. having a faster-to-initialize and lower power usage to boot (10mA for those 30ms, rather than for 100mA for 2000mS), you'll grossly cut down your power consumptions.Ī current-controlled power supply will often tell you the current-usage. If you need low-power but still wireless and more updates than that. There are practical limits (is one connection per day sufficient?), but 15 minutes still has some leeway depending on the application. etc.) until your current consumption is as low as you want. Have you tried going even slower? You can cut your current usage in half by going every 30-minutes, and then in a quarter by connecting every 60-minutes (etc. At this point, the active power usage during the 5-6 seconds of WiFi is already 2X the power consumption of the 15 minutes of Deep Sleep, so I have not attempted to reduce the idle consumption any further. But waking it up every 15 minutes, for 5-6 seconds of WiFi time, reduces the battery life to about 4-5 months. In theory, that's enough for 1 year of life on a single charge of a 2000 mAh battery. On my D1 Mini boards, I get about 0.22 mA in Forced Deep Sleep mode. But these dev boards often contain a voltage regulator which consumes a quiescent current. D1 Mini, NodeMCU) do support waking up from Deep Sleep. Hell, you might do better with LoRa (long-range, ~3-miles) signals than WiFi. I mean, WiFi just wasn't designed for low-power like these other protocols. The current-usage on WiFi power is just nuts.Īnyone trying to do wireless with low power should be using other protocols. Unfortunately, the ESP-01 module does not support this (without hardware hacking), because it does not expose the GPIO16/D0 pin necessary to trigger the RESET. It can then connect to WiFi, transmit the data payload, then go back to Deep Sleep again. If the WiFi is needed only intermittently, the ESP8266 can be placed into "Forced Deep Sleep" mode, with the internal RTC configured to wake it up after a certain time, e.g. But that still means about 5.5 years on a single charge. The lowest current that I have measured personally is 0.04 mA on various ESP-01 modules. 3xAA NiMh, or 1x18650 Li-Ion), that means over 11 years on battery, if no other work is performed. If WiFi is not needed, the ESP8266 can be placed into "Forced Deep Sleep" mode, with an idle current of 0.02 mA. In normal usage, WiFi apparently has a continuous drain of ~70 mA. During initialization, I believe it can consume 500 mA or more. It should draw about 15-16 mA, which is pretty close to the 18-24 mA measured in the TFA. The `delay(1)` triggers the "Automatic Modem Sleep" mode, which keeps the WiFi connection alive. The ESP8266 has 5 sleep modes, as summarized by this README.md in the Arduino ESP8266 Core.
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