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Output voltage monitor circuit ideas

R

Rappinglove

Jan 1, 1970
0
Hello Group,
I am looking to designing an output monitor circuit for a power supply
with up to 10 outputs. These outputs could be from 2V to 48V
The input supply for the circuit must not be above 28V 2A
The output will be LEDS lighting to show that the output has dropped
out.
Must have a quick response time, if the output drops out for a few ms I
need to know about it.

I was thinking a comparator type circuit comparing output with 0V and
then an LED switching on to alert the user that the output had dropped
out. Any other ideas or circuits?

Thank you
Dan
 
F

Fred Bloggs

Jan 1, 1970
0
Spehro said:
How do you define "drops out"? Comparing with 0V is probably not what
you want-- with perfect components it will never get to zero.

Maybe you want a voltage divider (dividing the output voltage down to
something around 1.3V, then compare against a ~1.25V reference, and
trigger a one-shot of ~0.5 second to blink the LED even with a short
drop of a few % from nominal.

But why do you want to do this? Why would the voltage drop? Is there a
better solution than just detecting this mystery drop (due to
mechanical contacts or something?).



Best regards,
Spehro Pefhany

There is no concept of anything other than ON or OFF, and that's final-
so why do you want to complicate the issue by asking all those
questions!!!!!! LOL.
 
S

Spehro Pefhany

Jan 1, 1970
0
Hello Group,
I am looking to designing an output monitor circuit for a power supply
with up to 10 outputs. These outputs could be from 2V to 48V
The input supply for the circuit must not be above 28V 2A
The output will be LEDS lighting to show that the output has dropped
out.
Must have a quick response time, if the output drops out for a few ms I
need to know about it.

I was thinking a comparator type circuit comparing output with 0V and
then an LED switching on to alert the user that the output had dropped
out. Any other ideas or circuits?

Thank you
Dan

How do you define "drops out"? Comparing with 0V is probably not what
you want-- with perfect components it will never get to zero.

Maybe you want a voltage divider (dividing the output voltage down to
something around 1.3V, then compare against a ~1.25V reference, and
trigger a one-shot of ~0.5 second to blink the LED even with a short
drop of a few % from nominal.

But why do you want to do this? Why would the voltage drop? Is there a
better solution than just detecting this mystery drop (due to
mechanical contacts or something?).



Best regards,
Spehro Pefhany
 
D

DaveM

Jan 1, 1970
0
Rappinglove said:
Hello Group,
I am looking to designing an output monitor circuit for a power supply
with up to 10 outputs. These outputs could be from 2V to 48V
The input supply for the circuit must not be above 28V 2A
The output will be LEDS lighting to show that the output has dropped
out.
Must have a quick response time, if the output drops out for a few ms I
need to know about it.

I was thinking a comparator type circuit comparing output with 0V and
then an LED switching on to alert the user that the output had dropped
out. Any other ideas or circuits?

Thank you
Dan



A
 
D

DaveM

Jan 1, 1970
0
Rappinglove said:
Hello Group,
I am looking to designing an output monitor circuit for a power supply
with up to 10 outputs. These outputs could be from 2V to 48V
The input supply for the circuit must not be above 28V 2A
The output will be LEDS lighting to show that the output has dropped
out.
Must have a quick response time, if the output drops out for a few ms I
need to know about it.

I was thinking a comparator type circuit comparing output with 0V and
then an LED switching on to alert the user that the output had dropped
out. Any other ideas or circuits?

Thank you
Dan


Dan,
I don't think you want to compare the output voltages to 0V. What if the output
voltage just sags below a specified voltage; not necessarily going all the way
to 0V... wouldn't you want to know about that as well? What constitutes a
drop-out? The voltage falling all the way to 0V, or below a specified
threshold?
A bank of LM339 quad comparators would probably do your job. Three chips, and
you even have a couple comparators left over.
Make a reference voltage source of about 1V, and scale the power supply outputs
to 1V. Connect the reference to one comparator input, the scaled outputs to the
other. Send the comparators' outputs into 555 one-shots if you want a momentary
flash when the voltage drops. If you want the LED to latch on when the
comparator trips, send the outputs into a D-latch. Of course, the LEDs connect
to the 555 flasher or to the latch output.
That should do it.

--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some days you're the dog, some days the hydrant.
 
J

Joerg

Jan 1, 1970
0
Hello Dan,

I am looking to designing an output monitor circuit for a power supply
with up to 10 outputs. These outputs could be from 2V to 48V
The input supply for the circuit must not be above 28V 2A
The output will be LEDS lighting to show that the output has dropped
out.
Must have a quick response time, if the output drops out for a few ms I
need to know about it.

I was thinking a comparator type circuit comparing output with 0V and
then an LED switching on to alert the user that the output had dropped
out. Any other ideas or circuits?

Comparators are a good option but don't compare with 0V, use something
higher. All comparators have offset errors. Also, as Spehro mentioned
you might need to decide for each output a level below which you'd
consider it "dropped out". IOW, where the connected circuitry would quit
functioning.
 
E

ehsjr

Jan 1, 1970
0
Rappinglove said:
Hello Group,
I am looking to designing an output monitor circuit for a power supply
with up to 10 outputs. These outputs could be from 2V to 48V
The input supply for the circuit must not be above 28V 2A
The output will be LEDS lighting to show that the output has dropped
out.
Must have a quick response time, if the output drops out for a few ms I
need to know about it.

I was thinking a comparator type circuit comparing output with 0V and
then an LED switching on to alert the user that the output had dropped
out. Any other ideas or circuits?

Thank you
Dan
Opto's holding SCR's off.
Ed
 
R

Rappinglove

Jan 1, 1970
0
Hello I do Halt (highly accelerated Life Testing) on varying power
supplies. This involves stressing units to extremes of temperatures
and vibration testing.
I want a one trick box that will work for all power supplies with up
to 10 outputs. I see what u r saying with the regulation issue.
Ideally I would measure about 2% output dips but comparing with a 1V
regulated signal would do as a minimum.
I was trying to keep things as simple as possible for the
initial ideas but as you ask, This is what I would like to achieve: 98%
of the output voltage at switch on would need to be stored and used for
the comparator signal with the actual output voltage. then triggering
an LED with an easy reset option.
 
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