S
swe_seeker
Guest
[As I don't trust my ASCII skills, I won't try to draw schematics or
curves here. Images can be viewed here instead:]
Circuit schematics:
http://thunderdome.myftp.org/diverse/battery/schematics.jpg
Oscilloscope curve for D flip-flop,clk in - /Q out to D in loop - Q out
Without modifications, and with IC5:1 lifted, respectively(bad brand):
http://thunderdome.myftp.org/diverse/battery/curve_no_mod.gif
http://thunderdome.myftp.org/diverse/battery/curve_leglift.gif
********************************************************************
Hi.
I use a 9V battery, a pushbutton and a D flip-flop to control /ENABLE
for a voltage regulator. This works just fine most of the time, as long
as I use one particular battery brand(I have two brands here at home, of
course there are more out there). If I use the other, bad brand the
flip-flop input starts to rise as it is supposed to, but halfway or
something into the rise the voltage on the input pin dips. So the
regulator /ENABLE never goes active. If I cut the connection between the
flip-flop output and the regulator then the flip-flop output does what
it should, i.e. go low to enable the regulator. On the other hand, if I
use the good brand - or a variable power supply - the dip never happens.
I've tried the same voltage as the bad battery, higher and lower as
well, for both the good battery brand(have a few of them) and the
supply. In both cases the circuit works. So my limited experience points
me towards the battery
].
Simple(open circuit voltage+voltage over ~120ohm resistor)
measurements of the internal impedances in the batteries gives ~55ohm
for the bad brand and ~8ohm for the good brand. Can that be the problem?
My interpretation of the oscilloscope curves is that the input signal to
the flip-flop is ok with the bad brand, but when the signal gets past
the flip-flop and tells the regulator to get going it all dips, because
the bad brand battery can't cope with it.
I've experimented a little with the decoupling, removing/adding
capacitors to decoupling/signal path between battery and regulator, but
no luck there.. Are the decoupling capacitors for 9V necessary? I mean,
shouldn't there be enough margin down to the 3V out from the regulator -
disregard Murphy's law - even if the 9V picks up some noise? Also, I'm
not really sure whether to add/remove capacitance? More capacitance
should help the battery when the circuit is enabled, as the capacitors -
should have - had plenty of time to charge up before the button is
pushed. But at the same time added capacitance means added load/strain
for the battery. Or? All comments are welcome, as I'm new to this.
Thanks in advance, and hope this makes sense :*].
curves here. Images can be viewed here instead:]
Circuit schematics:
http://thunderdome.myftp.org/diverse/battery/schematics.jpg
Oscilloscope curve for D flip-flop,clk in - /Q out to D in loop - Q out
Without modifications, and with IC5:1 lifted, respectively(bad brand):
http://thunderdome.myftp.org/diverse/battery/curve_no_mod.gif
http://thunderdome.myftp.org/diverse/battery/curve_leglift.gif
********************************************************************
Hi.
I use a 9V battery, a pushbutton and a D flip-flop to control /ENABLE
for a voltage regulator. This works just fine most of the time, as long
as I use one particular battery brand(I have two brands here at home, of
course there are more out there). If I use the other, bad brand the
flip-flop input starts to rise as it is supposed to, but halfway or
something into the rise the voltage on the input pin dips. So the
regulator /ENABLE never goes active. If I cut the connection between the
flip-flop output and the regulator then the flip-flop output does what
it should, i.e. go low to enable the regulator. On the other hand, if I
use the good brand - or a variable power supply - the dip never happens.
I've tried the same voltage as the bad battery, higher and lower as
well, for both the good battery brand(have a few of them) and the
supply. In both cases the circuit works. So my limited experience points
me towards the battery
].Simple(open circuit voltage+voltage over ~120ohm resistor)
measurements of the internal impedances in the batteries gives ~55ohm
for the bad brand and ~8ohm for the good brand. Can that be the problem?
My interpretation of the oscilloscope curves is that the input signal to
the flip-flop is ok with the bad brand, but when the signal gets past
the flip-flop and tells the regulator to get going it all dips, because
the bad brand battery can't cope with it.
I've experimented a little with the decoupling, removing/adding
capacitors to decoupling/signal path between battery and regulator, but
no luck there.. Are the decoupling capacitors for 9V necessary? I mean,
shouldn't there be enough margin down to the 3V out from the regulator -
disregard Murphy's law - even if the 9V picks up some noise? Also, I'm
not really sure whether to add/remove capacitance? More capacitance
should help the battery when the circuit is enabled, as the capacitors -
should have - had plenty of time to charge up before the button is
pushed. But at the same time added capacitance means added load/strain
for the battery. Or? All comments are welcome, as I'm new to this.
Thanks in advance, and hope this makes sense :*].