Hi,
I want to run a Attiny85(which works between 1.8V - 5V) from 1.5V battery. Is it possible?
Thank you
Why not just try it? The datasheets have limits for a reasons. Perhaps some of it works and other parts of it doesn’t... again outside the limit is not reliable otherwise they would include the range. Some of it is due to CMOS switching circuitry internal which require a minimum voltage... other may be due to the clock speeds... try it and document what you find.
If you are asking about 1.5v I imagine AA or AAA. What happens when it goes to 1.2 or 1.1v or somewhere in between?
I think if it all functioned as it should at 1.5 Atmel (now Microchip) would love to claim that.
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Another thought put in a boost converter
if it was possible to make clock works slower, would that mean that it could possibly work better with 1.5V? if not, what processor to use similar to attiny85 that would work with 1.5v?
just try it...i don't have an encyclopedia of microprocessers handy... not much works below 1.7V which is the lowest voltage digital level that I'm aware of.
There must be a CMOS logic working at much lower voltage (proof: simple quartz clock work down to <1V) but it is rare for"general purpose" electronics.
My guess is the ATTiny will work at reduced clock speed until you hit the POR threshold.
But it is known RAM stays intact event under the POR and needs only a few nA of current and about 0.6V IIRC. But I don't think the CPU is alive at the moment.
Also note the ATTiny85 needs at least 2.7V, you need ATTiny85V for low voltage according to the datasheet.
theoretically they have gotten CMOS to work down to 0.2V (IEEE) but it's not practical for most purposes. Even 1.7V is rarely seen in practice... might change to improve battery life in the future.
I consider being able to run from a single alkaline/NiMH cell very practical. I have never considered the option to go under 1.8V. It may be interesting to try. But the datasheet says the falling POR is 1.3V (typ)/1.6V (max) - probably still not usable with single cell.
how do you switch a mosfet at that level? will it be the same current per pin? lower voltage creates its on set of challenges. also no idea whether the memory works... what happens to the clock... etc. It does sound like an interesting experiment.
keep in mind if you power it at that level then plug it into USB to program the circuits that are biased for 1.5V may not like it.
Can you program flash at 1.5V???
All kinds of issues...
Programming of flash/EEPROM will probably fail.
I did a quick experiment - one ATTiny13A programmed at 5V running from the internal WDT oscillator is blinking a LED (powered via a BJT from 5V). It is running down to 1.5V, nearly exactly, POR is triggered around 1.49V. So far (a few minutes) it is still blinking so both the HW timer and SW timer counting overflows works well. I will let it run until tomorrow and see if it is still alive.
chris700:
I want to run a Attiny85(which works between 1.8V - 5V) from 1.5V battery.
Why? Size?
You can get small LiPo cells. And 10440 size Li-ion, which are same size as AAA. These batteries are ~3.7V.
Cost? Safety (alkaline leak, lithium explode)? Size (common alkaline/zinc-air is much smaller than lithium)? Academic?
EDIT: My test ATTiny was running from 1.5V for the whole night. It was far from a rigorous test but I would conclude that for device that is allowed to fail it is possible to assume it will work down to POR threshold if the clock speed is low enough.
OTOH I have seen AVR doing "strange things" when the clock speed is too fast for supply voltage. Such as being stuck in some strange unresponsive state or bootloader erasing part of itself.
EDIT2: The safety advantage of alkaline cells is relative. Swallowing a small alkaline coin cell is much easier than lithium but both are lethal!
Construct a simple boost inverter, I'd suggest a joule thief. The voltage can be clamped by zener diode or better yet the inverter can be switched on and off using some low voltage comparator circuit to keep the output at the desired potential.
I found that. It seems to work. I will test it when i receive the parts.
original post: Technoblogy - Powering Projects from a 1.5V Battery
Smajdalf:
Programming of flash/EEPROM will probably fail.I did a quick experiment - one ATTiny13A programmed at 5V running from the internal WDT oscillator is blinking a LED (powered via a BJT from 5V). It is running down to 1.5V, nearly exactly, POR is triggered around 1.49V. So far (a few minutes) it is still blinking so both the HW timer and SW timer counting overflows works well. I will let it run until tomorrow and see if it is still alive.
i tried my Attiny85 but it doesnt work with one led light only. I assume i might have the higher voltage version. Ill buy the one that works from 1.8 so i can test it. thanks for your help!
You cannot light a LED without another power source and a step up. Only IR LED.
Smajdalf:
You cannot light a LED without another power source and a step up. Only IR LED.
yea thats what i mean. but i just checked i have the attiny85 20. which means i cannot power it even with 1.8. ill order the 10 version
What’s the forward voltage of the LED?
wolframore:
What’s the forward voltage of the LED?
for a red i guess 1.7-2.8 right?
so how do you drive that using 1.5V battery?
It's one thing to run a chip at low voltage but doing anything like driving an LED or switching a mosfet gets near impossible.