Has anyone had any luck using a DC-DC boost IC for very low power devices. I imagine they are not very efficient at low currents. Most of the time the atmega will be asleep drawing only 20uA.
pinMode(DHT_PWR_PIN,INPUT);digitalWrite(DHT_PWR_PIN, LOW);// dht22 powered downpinMode(DHT_PWR_PIN,OUTPUT);digitalWrite(DHT_PWR_PIN, HIGH);
I find if I remove the wire DHT_DATA -> arduino pin 12 the current drops to 4.2uA.
Read the data sheet. It has a high efficiency and a low quiescent drainage.
I've no idea why you'd want to use this NCP1450 ic to boost a single AA cell to 5v. This appears to require an input of 6v and offers 3.3v out.
Do you have the DHT-22 pull-up resistor installed (10K)? That probably draws a bit.Oddly enough I am making something similar. I was planning to use 3 x AA batteries. I was also planning to use a transistor (MOSFET) to turn on and off devices between readings, to save power. Your code which turns the power pin on and off should achieve the same result. I was thinking though of turning on and off a SD card.Just out of curiosity, did you find the DHT-22 read high with its temperature? I found it reading 25 C when other measurements gave 22 C in exactly the same spot.QuoteI find if I remove the wire DHT_DATA -> arduino pin 12 the current drops to 4.2uA.Try setting that to input as well when you power the device down.
A boost regulator can be very worthwhile for a low power board. I use an MCP1640 for a low-power data logger that I designed. The logger runs on two AA cells, yet when actively logging, the regulator provides 3.3V or 5V. The regulator can actually increase usable battery life because it can still produce the regulated voltage even when the batteries have run down. The MCP1640 has a control pin that allows the MCU to enable it, or just to pass the battery voltage straight through. The MCU can control not only the regulator, but also power to the sensors, EEPROM logging memory, and real-time clock. After logging, the MCU powers off the EEPROM, RTC, and sensors, lowers its clock frequency to 1MHz so that it can operate down to 1.8V, disables the regulator and goes to sleep. The RTC provides an interrupt to start the next logging cycle, when the reverse happens: enable the regulator, increase system clock to 8MHz, power up the sensors, memory, RTC. The board consumes less than 5µA while sleeping. For low-rate logging (e.g. once per minute) I think the battery could easily last a year or more. With a few simple sensors, the logging cycle only takes about 10ms, so the duty cycle works out to zero, to three or four decimal places.
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