36

The Atmega328 provides six power saving modes, ordered from minimal to excellent (estimated current consumptions from this forum post): SLEEP_MODE_IDLE: 15 mA SLEEP_MODE_ADC: 6.5 mA SLEEP_MODE_PWR_SAVE: 1.62 mA SLEEP_MODE_EXT_STANDBY: 1.62 mA SLEEP_MODE_STANDBY : 0.84 mA SLEEP_MODE_PWR_DOWN : 0.36 mA Quoting the original question: I figured I could put ...


29

A low-current method I used once was to connected a switch between two microcontroller I/O pins. One I/O was configured as an output (SWO). The second was configured as an input (SWI) with its programmable internal pull-up enabled. The switch state was sampled infrequently (every 10 ms) by a software interrupt routine. The reading sequence was: drive SWO ...


26

A relatively large lithium primary cell would be my choice. They are specified for something like 10 or 20 year life running water meters, including periodic radio communication. And maybe a second cell to run the motor so it stays relatively fresh. The Israeli company Tadiran makes such products. As long as the temperature does not get too high the ...


24

If I understand you correctly, you want a charger than can switch between battery and input source (i.e. when adapter is plugged/unplugged) to power the load. There are plenty of charge control ICs and circuits around that can do this. The MCP73831 is a nice cheap little Li-Ion charge IC, and with the addition of a PMOS/Schottky, can switch between ...


23

A SPDT (Single Pole Double Throw) button would be your ultra efficient button. Source: http://www.ni.com/white-paper/3960/en/ In your case the 1P would go to the MCU, the 1T to VCC, the 2T to GND.


21

Realistically it's very difficult to measure to that system level of accuracy. The particular sensor you show is DIN class A tolerance, meaning that the maximum error of the sensor alone is 150mK + 2mK*|T| (with T in degrees C). So at 100 degrees C, the maximum sensor error alone (not counting self heating) is 350mK, 35 times what you say you want. This type ...


21

If you want power-saving, put the MCU to sleep. The relevant instructions are WFI and WFE: wait-for-interrupt and wait-for-event, respectively. WFI is kind of self-explanatory: it wakes up when you get an interrupt. (The interrupt must be enabled, though!) WFE might merit a bit more explanation. To use it, it's probably enough to know that if you set ...


21

It depends how much force you need. In general, you need quite a bit of current to run even a really tiny solenoid (hundreds of milliamps), and you need to hold that current to keep the solenoid pulled in or pushed out (depending on configuration). The force is proportional to the magnetic field, which is a product of the number of turns and current through ...


19

If you're budgeting 0.3 mA average every µA counts. Not so much of a problem for the microcontroller, but the SD card will consume tens of mAs. You want to have it switched on as little as possible. But the ATmega328P has only 2 kB of RAM, so that means your sample buffer will be full in less than half a minute, and then it's time to write to the SD ...


19

I have an Arduino Pro Mini on my desk right now that is running off 2 AA batteries and could run for over a year if required. There are three aspects of the design that have achieved this. 1. A different regulator I'm using a LTC3525 boost regulator. It has very low quiescent current (7uA) and high efficiency (>90% @ 0.2mA). Something like this sparkfun ...


19

It does not appear in your equation because this equation assumes you're using the battery at its output voltage during the whole usage without conversion. This is not the case here, because you're using a step-down converter. So, to build the correct equation you: get Vavgbat: the average voltage of the battery during the whole discharge cycle: the ...


18

You aren't entering the lowest power mode. Take a look at AN11027. Regular sleep mode yields single digit milliamp consumption, as you have seen. Deep sleep mode is in the single digit micro amp range. Deep power down is a few hundred nanoamps. Also be careful of things in the surrounding circuit which can steal power (or even supply it, invalidating ...


18

Use an extension cord to get the AC the required distance, then use the power adapter.


17

I think the main problem is: vias could occupy significant space from other components, thus a larger board is necessary. On the first picture a TH vias allow us only four pads to be placed. But with a blind via or without a via we have place for six (or more if we have more rows) pads. A larger BGA component could be placed here this way. source And at ...


16

Perhaps the dimmer circuit won't work without a resistive load. Some thyristor dimmer circuits might not see enough holding current from a rectifier-capacitor load to stay on for the half cycle. You may be able to wire a fat resistor in parallel with the LED lamps and have it work, however it may require some experimentation to determine an appropriate value....


16

One of a line of products I worked with and designed for was a smart payphone; think a microcontroller that operates as if it were a payphone. These had to operate on an ordinary telephone loop, with a guaranteed 20mA supply (but not guaranteed to be higher); in the on-hook condition the unit was permitted only a few microamps of leakage current as the ...


16

The switch is available in Gold (Au) and Silver (Ag) alloy. Gold allows switching of low voltage and current signals, such as measurements. Silver allows switching of high voltage and current, such as power and coils. This difference is because the contact material degrades over time and per switching action, and a low voltage might not be able to get any ...


15

(Answering my own post with useful information) I have performed some experiments with a limited set of SD cards to check their power consumption. They seem to vary widely between manufacturers and within types, some cards consume 10 times more sleep power than others. There are two results below. The first is a the estimated current consumption when ...


15

The most likely answer is that he didn't. While that was the claim, it is much more likely that he swapped out the frame soon before the painting went up for auction. Dave Jones from the EEVblog did a video on this: https://www.youtube.com/watch?v=SdKdQWhlNTY UPDATE Here's a follow-up video from the EEVblog: https://www.youtube.com/watch?v=8dbYGefDdWo


14

All of these comments are spot on. I would like to add a few more suggestions: 1) For LEDs, use high output 20 mA LEDs. Here's the logic. Lets say you want a dim status LED that blinks every 8 seconds. You don't want it to be bright, so you use some random LED. The problem is, a dim LED still uses 20 mA (or more) to output only 100 mcd. Instead, get ...


14

Yes, but no. Yes, you can use two pins to source more current, or in your case, source less current out of each. This is a common practice, but not often used on Microcontrollers. Devices like led drivers, or ULN2803 Motor Drivers, or connecting multiple transistors in parallel. Even multiple resistors in parallel. On a microcontroller, not really designed ...


14

A lot of battery-operated devices need to optimize for power consumption, and µA currents are frequently involved (sometimes even nA). To give an example, consider wireless remotes. They may have just a 3V, 200mAh battery. If you want this remote to work 10 years without necessitating battery change, that's just 20 mAh/year. Or 0.054 mAh/day, or 0.0022 mAh /...


13

If you cut the wire near the adapter and extend it from 1.5m to 10m, you can use wire that has 7 times the cross-sectional area and it will behave similarly to 1.5m of wire. That means that the copper (not insulation) diameter must be \$\sqrt{7} = 2.6\$ times the diameter. An IP camera I happen to have on my desk here has an adapter that is rated 5V/2A ...


13

I wouldn't say that vias are bad. They are not! One useful way to use vias is to shield RF energy in a RF board, a technique called via stiching:


12

TI's MSP430 is well known for its low-power: I've used the MSP430F1101 in an application which included the microcontroller, a voltage regulator and a reset circuit, which, with the controller active, consumed less than 5\$\mu\$A typical. It depends on your needs. My controller didn't need high speed, so I could operate it on a 32.768kHz crystal, which ...


12

LCD display without back-light is the only possible solution on these conditions. Something like this: Here is some example data sheet: Link to PDF


12

a better idea for this, if you want to use a PMOS high side switch, would be to have the ATSAMD21 switch a low-side NPN switch, which then switches the PMOS for the SIM530. Example: simulate this circuit – Schematic created using CircuitLab R2 (arbitrarily chosen to be 50x R1) pulls Q1 to ground (off) if D1 is in high impedance state, which it may be ...


11

What you suggest is possible, but you have to be aware of some gotchas. The biggest issue is for the transistor to not distort the measurement. You didn't give any accuracy requirements, but let's say it's a 10 bit A/D and you don't want the transistor to add more than 1 count of error. On the 3.3 V scale, one count of a 10 bit A/D is 3.2 mV. With the ...


11

It is just one of the parameters you can use to tweak the autorouter. Via's add a little cost in drilling (even though this might not be explicitly shown on the bill), they take up space, and other things being equal it is better for a route to stay on the same layer. I can imagine (but I am not sure) that a via is just a little bit less reliable than a ...


11

There are a number of possible issues. Too many to list in a comment. So I will list them here instead. First, safety. If each cell has protection already, then that is good. I would definitely recommend you use protected cells in this application. But if not, at least make sure you insert some kind of current limiting device between charger and each cell. ...


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