Hey guys,
In most of my projects i put my attinies/mega to sleep to save power, but as i use modules, ex ctc clocks or sdcard modules, the led stays on.. is this a problem? How much do those small square leds can affect battery life of projects? Is there a way i can make a project with those off? Thanks!
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spycatcher2k:
In my low power projects, if I use the modules with LEDs built in, I usually remove the current limiting resistor for the LED (easier to replace if needed than an LED). I've seen 'passive' modules taking 20mA when not being accessed. I've not had an issue YET, but that does not say some designer won't use the LED as a functional part.
Ok so 20 mA seems pretty big.. Then if I take the resistor off, it helps? im not sure I see why. And if I take the led off the module, would it ne even better? And are relays an option? Sorry for all those questions
LED and resistor are in series. If you remove EITHER of them the circuit is broken and no current flows.
Steve
Ok so I feel like im out of ideas. Could some sort of relay switch cut power to modules when not in use? Since i cant modify the modules, i need a solution that shuts power
JCSB:
Could some sort of relay switch cut power to modules when not in use? Since i cant modify the modules, i need a solution that shuts power
You could switch the power to other modules with a p-channel mosfet.
If your Arduino and modules run on 5V, then one of these FQP27P06 P-Channel MOSFET will do ok (bit big, but cheap)
If the Arduino/modules run at 3V, then it's a bit trickier to get a device that will work at that lower voltage.
The FDN340P is ideal (it's used on some Arduino boards) but it is a surface-mount part.
This ZVP4424A will also do if you only need to supply 100mA and it is a thru-hole device.
Yours,
TonyWilk