let's see youtubers here is the guy with
the Swiss accent there were some
discussions concerning the correct
powering of an esp8266 amongst my
viewers so I thought I use the things we
learned in the latest videos and use it
to find the influence of different
measures on the behavior of our esp8266
one can we enhance stability of the
esp8266 with capacitors across the power
pins what is the optimal size and
technology to what about this if we use
a voltage regulator 3 how can we reduce
power consumption during deep sleep with
and without voltage regulators and 4 can
we use an old MCU board for deep sleep
low energy applications I will use two
different esp8266 one barebone without
any resistors and capacitors mounted on
a small PCB and the other mounted on a
PCB with the necessary resistors for
chip enable and GPIO 15 and an HT 7 3 3
3 low dropout voltage regulator in the
first test I used the barebone ESP and
connected to a 3.3 volt bench power
supply I measure the current using the
microcurrent gold discussed in video
number 84
the results are basically the same as in
video number 47 the bigger the capacitor
the smaller the current spike viewers
ask me if these spikes are dangerous for
power supplies or voltage regulators
these days most voltage regulators have
over current protection so this is not
dangerous for them but what do they do
to protect themselves they lower the
voltage during this over current period
and this is potentially dangerous for
our ESP because if it does not get
enough voltage it crashes officially the
specifications of the ESP a
266 says that it operates from 3 volts
to 3 point 6 volts but at room
temperature it works also at lower
voltages in addition to the potential
voltage drop of the regulator the wires
from the power source to the ESP have a
small resistor in series which again
drops some voltage according ALMS law
they drop more voltage with higher
currents so the expected effect at the
power pins of the ESP is that the
voltage fluctuates with the current
spikes the better the power supply or
the lower the resistor of the wires the
smaller this effect
let's check we measure the voltage
across the VCC and ground pins of the
ESP without a capacitor the voltage drop
in my configuration is 0.4 volts this is
mainly because the resistor of the leads
and the breadboard if I add just one ohm
to this wire resistance I get a voltage
drop of 0.6 volts let's assume we power
our ESP with 3.3 volt then the lowest
voltage is 2.9 volt without the
additional resistor and 2 point 7 volt
with the additional resistor which is
already outside the specifications of
the ESP this means that on the bad
conditions like high or low temperature
it can crash from time to time and this
is what some users of esp8266 experience
what are the options to deal with this
problem we could use a higher voltage
for example 3.6 volt this is the maximum
of the specs then of course we would
still be in specs for both of the above
conditions or we reduce the resistance
of our leads by shorten it or use
thicker wires if the resistance comes
from the inner resistance of the battery
we could also use a bigger one but
because the spikes are very short we
could also try to reduce them with
either a capacitor across the power
or by an inductor in series with the
power wires together with louis bikes we
expect also less voltage drop I did this
in video number 47 but for now we look
at the voltage drop with a capacitor of
100 micro farad 330 micro farad and 1000
micro farad it is important that this
capacitor is close to the power points
of the ESP because we want to reduce the
resistance between the capacitor and the
ESP itself now the voltage drop is less
than 0.2 volt even with a resistor from
before problem solved
we never go below the 3 volt if we add
an inductance the problem becomes bigger
not smaller this is not what I expected
but if we look at the 470 micro Henry
inductor we see that it has a 1 point 4
ohm resistor which is in series with all
other resistance this seems to be the
main effect at least for this inductance
I tried with different inductors but
with no success by the way an inductor
without the capacitor regularly crushed
my ESP summarized we can say for long
wires or weak batteries it is good to
use a big capacitor across the power
pins of the ESP or you increase the
voltage of your power source batteries
like the live April 4 from my video
number 64 or 65 changes its voltage
during discharge smaller voltage drops
during current spike means that we can
use more of the battery capacity before
our ESP becomes in stable just as an
indicator my barebone ESP crashes at
about 2.3 volt at room temperature of
about 22 degrees Celsius very good
compared to specs needless to say this
is without any pins used for a real
application
maybe I will heat or cool a device in a
future video
to find out if this behavior changes
with temperature so we can go on to our
next topic the deep sleep without any
capacitor we measure around 22 micro
ampere deep sleep current if we add our
normal 1000 micro farad capacitor we get
about 24 micro ampere if we replace this
1000 micro farad capacitor with an SMD
tantalum capacitor we get a surprise the
current increases to 45 micro ampere so
the capacitor has a leakage current
which is bigger than the sleep current
of the ESP as one of my viewers told me
that this is a well-known feature of
these big capacitors if we replace it
with a 330 micro farad SMD tantalum the
current drops to 24 micro ampere again
so there seems to be a big difference
between the two capacitors I do not know
if better 1000 micro farad capacitors
exist for me this means that I will use
an aluminium electrolytic capacitor for
my low energy applications summarized
our barebone ESP with the right
capacitor is a good choice for low power
applications some viewer asked me also
about deep sleep and note MCU boards
because the node MCU boards have a few
more components and generally a
different voltage regulator they cannot
be used for low power applications even
in deep sleep they still draw about 10
milliampere which is way more than the
ESP itself now let's go on with the ESP
and a low drop out voltage regulator
this is a typical application if we use
a lipo battery or a 5 volt power source
I start with 5 volt input voltage and a
10 microfarad capacitor required by the
datasheet of the voltage regulator now
the voltage drop is 1 volt this is
because this regulator can
not react very fast and is only
specified for 250 milli ampere current
so it drops voltage exactly as expected
I checked all my note MCU boards and
most of them use an AMS 1 1 1 7 voltage
regulator they use only small capacitors
and they show very similar behaviors the
only exception is the Bemis d1 mini
which uses another voltage regulator
which is much better suited for this
purpose so just using a 10 micro farad
capacitor is not recommended we need a
much bigger capacitor let's again go
with a 330 micro farad here we have 0.4
volts drop and with a thousand micro
farad we have less than 0.1 volts which
is okay so again if we use a 3.3 volt
regulator and the 1000 micro farad
capacitor this is a good choice
summarized with the AMS 1 1 1 7 or the
HT 7 3 3 3 voltage regulators we need a
beefy capacitor otherwise we might
experience crashes if our other
components allow you could also use a 3
point 6 volt regulator instead of a 3.3
volt one the last step is now the deep
sleep with a voltage regulator and the
low loss 1000 micro farad capacitor at
my first test I measured around 80 micro
ampere which is way too much
investigations showed that the reason
for that was a simple 10k resistor on
this small board which bridges the input
and the output pin of the regulator it
can be replaced by a 0 ohm resistor if
you do not want to use a voltage
regulator after removing this
unnecessary resistor everything is ok
and we see the expected 24 micro ampere
deep sleep current summarized the HT 7 3
3 3 really has a very low and present
current of a few micro ampere and not as
some data sheets suggests a few
milliampere
I hope you got the necessary information
on how you have to configure your ESP
power supply for stability and low
current consumption during deep sleep by
you