The current barrel jack input implementation used an AMS1117 linear regulator, which can be fairly inefficient especially when the input voltage is high. Maybe instead of the AMS1117, a switch-mode power converter like LM2596-5.0 can be used. This will allow the board to run much more efficiently. The same also applies for the 3.3V rails with LM2597-3.3.
These are nice suggestions. They will likely cut down the power consumption by 50% or more on any arduino board running on AC adapter or battery. Coupled with sleep mode, this could really make a huge difference in how long a project can last on battery. I'm all for it.
Since raspberry pi has launched zero, $5 computer, arduino boards need to upgrade so it stands out in the low power direction.
Thanks for the part numbers. I'll explore them myself.
liudr:
These are nice suggestions. They will likely cut down the power consumption by 50% or more on any arduino board running on AC adapter or battery. Coupled with sleep mode, this could really make a huge difference in how long a project can last on battery. I'm all for it.Since raspberry pi has launched zero, $5 computer, arduino boards need to upgrade so it stands out in the low power direction.
Thanks for the part numbers. I'll explore them myself.
I am going to try laying out a LM2597/CH340G Arduino-compatible and share it here. two LM2597s plus the magnetics can be a bit expensive so I included some cost management by substituting in the cheaper CH340G USB to UART adapter. Also the LM2597 provides a Power Good pin that can be used to hold the board in reset until the power is ready.
can be a bit expensive
There's the rub. An LM2597 is more expensive than the ATmega328, and under "typical" usage, isn't that much more efficient than a linear regulator (switching regulators tend not to be that efficient at low loads, like the <100mA Arduino circuitry. )
You have to decide what you're really aiming for. A "low power" arduino aimed specifically at battery operation would be a good thing, but replacing the regulator is not all that you'd want to do, and the design would/should probably look different for a "longest possible operation of a low power circuit from 4AA batteries" than it would for a "I really need 1A@5V for the rest of my 12V car project.")
westfw:
There's the rub. An LM2597 is more expensive than the ATmega328, and under "typical" usage, isn't that much more efficient than a linear regulator (switching regulators tend not to be that efficient at low loads, like the <100mA Arduino circuitry. )You have to decide what you're really aiming for. A "low power" arduino aimed specifically at battery operation would be a good thing, but replacing the regulator is not all that you'd want to do, and the design would/should probably look different for a "longest possible operation of a low power circuit from 4AA batteries" than it would for a "I really need 1A@5V for the rest of my 12V car project.")
When you hook up 5 or 6 sensors to it it starts to chew current. Also if you are stepping down 12V to 5V using AMS1117 you are looking at at at most 42% efficiency. I doubt if there is a buck converter that cannot beat this (including MC34063) Also those buck converters usually have a wider input range than AMS1117: MC34063 can go as high as 40V and LM2597HV-5.0 allows for a 60V input rail.
If I aim to create a battery-operated Arduino clone I would have the 16U2 to double as a boost-buck controller: boost the battery voltage (2.8V-4.2V) up to 5V then buck it to 3.3V for some peripherals. This means I just need to add two MOSFETs - maybe a single AO4606 as it comes with both the PMOS (for the buck) and the NMOS (for the boost)
westfw:
There's the rub. An LM2597 is more expensive than the ATmega328, and under "typical" usage, isn't that much more efficient than a linear regulator (switching regulators tend not to be that efficient at low loads, like the <100mA Arduino circuitry. )You have to decide what you're really aiming for. A "low power" arduino aimed specifically at battery operation would be a good thing, but replacing the regulator is not all that you'd want to do, and the design would/should probably look different for a "longest possible operation of a low power circuit from 4AA batteries" than it would for a "I really need 1A@5V for the rest of my 12V car project.")
Found this chip and maybe it can work: ACT4088. This is a step-down converter with 1.4MHz switching frequency (so magnetics involved can be tiny) and a shut down option (so the automatic power switch-over can be replaced with this and an 2N7002.) Maximum current output is 1.5A so more than enough to drive a small motor or two.
BOM for this step-down regulator, which can be duplicated for the 3.3V rail too:
- ACT4088 controller,
- SS34 Schottky rectifier
- 4.7uH 3A high frequency power inductor
- 220uF 16V tantalum filter capacitor (since it is SMPS output low ESR is critical, and I am giving it 10x capacitance as recommended in the datasheet to reduce ripple)
- 2x resistors
I'd say definitely this replacement is not useful for lots of projects but indeed useful for many projects with sd card, some network interface (wifi ethernet xbee etc.) then some sensors. Maybe also add a way to shut down 3.3V regulator on board to save power when sleeping. I found that even the smallest 328P arduino (complete with USB), the nano, will consume a good 45mA at 3.3V (2 AA batteries and a boost converter from sparkfun), when the processor is sleeping. My own data logger design shuts off everything (no led indicators) and consumes about 0.4mA on the same AA batteries and same boost converter but the 1117-3.3 is turned off. It'll run for months on 2 AA.