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On 2021-05-06 20:07, Robert D. Bowers wrote:
> Yes, especially back with the TTL devices.? I did encounter it a lot
> when working on machines that used a LOT of TTL

Power to chips.  Here's something that happened to my neighbor:

I was coding firmware at a networking equipment manufacturer, and Jimmy
the hardware guy was in the next cubicle.  He was tearing his hair out 
over
a CMOS barrel shifter.  This was a chip that would load an Ethernet 
packet and on every clock,the packet would proceed one step through the 
chip.  I think it was 32 bits wide.

Anyway the thing mostly worked.  But every third Tuesday, it would drop 
a bit.  Drove
him crazy for a week or two, but he finally got it.

*** There was no Vdd - that is, no power connected at the chip's power 
pin.  But this was CMOS, and it would cheerfully run off any input pin 
that happened to be high.  Being that this thing had a LOT of pins, 
there was (almost) always a high one somewhere.  But every third 
Tuesday, the fates would give the chip all zeros - just for a tiny 
fraction of a millisecond.  And it would lose its noodles.

    It was the sort of thing where you're amazed that it worked at all.

           - Jerry KF6VB

Yes, especially back with the TTL devices.? I did encounter it a lot when working on machines that used a LOT of TTL - I'm not sure exactly what chips, but some boards (card rack based devices) would pull more current when the voltage was getting low - especially when near the minimum operating voltage.? I liked to keep the voltage on those machines as close to 5v (on the boards) as possible - it kept things running better and longer (and cooler).? I could usually tell when low voltage was a problem, partially because of how warm certain boards would run.? (I don't remember which brands or models, much less the boards - over 20 years ago now).

I used to repair old CNC and NC machines... and some of them had hundreds of TTL.? The 5v power supplies for them were massive - I may still have one (switching type - for replacement) in my 'stuff' - something like 5 volts at either 75 or 100 amps, well regulated, and very well cooled.? Some of those machines had heavy buss bars instead of cables for power to the racks - one had buss bars that were over 5/8 inch wide, 3/8 thick, solid copper with silver plating.? The ground busses (two) were even bigger.? The power supply that fed that beast was massive (linear type) and required a forklift to move.

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On 5/6/21 10:26 PM, Jerry Gaffke via groups.io wrote:

Bob,

Have you noticed increased current draw when feeding less than the recommended voltage?
Exactly what sort of electronic device was this?

In my experience, that would be very unusual.

Jerry, KE7ER

On Thu, May 6, 2021 at 02:40 PM, Robert D. Bowers wrote:

Most of the time I encountered undervoltage issues, the symptoms
were pretty obvious and easily fixed.? The biggest thing I found
was increased current draw as the components were stressed.

Hi,
i have a uBitx v6 that i put together 4 months ago. Radio was working fine the last time i used it 4 months ago. Then i got the radio shipped to another location. Now when i switch on the radio, the LCD display lights up as expected and i can hear some white noise (although very low audio level) but the radio is unresponsive. Neither is the touch nor the rotary encoder seems to change anything on the display.

Steps followed to debug the issue until now

On Arduino and LCD side

• Tried to upload a basic blink led sketch to arduino - It uploaded and executed successfully so arduino is ok
• Added some serial.print statements to read value from rotary encoder -? Was able to successfully receive rotary encoder value in serial monitor
• Tried to upload a test sketch to check lcd -- Sketch uploaded and executed successfully was able to get touch inputs in serial monitor

So in my opinion Arduino, LCD and the rotary encoder seem to be working fine.

? On the? main board

• Retouched all solder point on the back of the board to make sure there are no cold solder joints?

Reference Video:

Yes, especially back with the TTL devices.? I did encounter it a lot when working on machines that used a LOT of TTL - I'm not sure exactly what chips, but some boards (card rack based devices) would pull more current when the voltage was getting low - especially when near the minimum operating voltage.? I liked to keep the voltage on those machines as close to 5v (on the boards) as possible - it kept things running better and longer (and cooler).? I could usually tell when low voltage was a problem, partially because of how warm certain boards would run.? (I don't remember which brands or models, much less the boards - over 20 years ago now).

I used to repair old CNC and NC machines... and some of them had hundreds of TTL.? The 5v power supplies for them were massive - I may still have one (switching type - for replacement) in my 'stuff' - something like 5 volts at either 75 or 100 amps, well regulated, and very well cooled.? Some of those machines had heavy buss bars instead of cables for power to the racks - one had buss bars that were over 5/8 inch wide, 3/8 thick, solid copper with silver plating.? The ground busses (two) were even bigger.? The power supply that fed that beast was massive (linear type) and required a forklift to move.


On 5/6/21 10:26 PM, Jerry Gaffke via groups.io wrote:

Bob,

Have you noticed increased current draw when feeding less than the recommended voltage?
Exactly what sort of electronic device was this?

In my experience, that would be very unusual.

Jerry, KE7ER

On Thu, May 6, 2021 at 02:40 PM, Robert D. Bowers wrote:

??? Most of the time I encountered undervoltage issues, the symptoms
??? were pretty obvious and easily fixed.? The biggest thing I found
??? was increased current draw as the components were stressed.

Bob,

Have you noticed increased current draw when feeding less than the recommended voltage?
Exactly what sort of electronic device was this?

In my experience, that would be very unusual.

Jerry, KE7ER

On Thu, May 6, 2021 at 02:40 PM, Robert D. Bowers wrote:

Most of the time I encountered undervoltage issues, the symptoms
were pretty obvious and easily fixed.? The biggest thing I found
was increased current draw as the components were stressed.

Most of the time I encountered undervoltage issues, the symptoms were pretty obvious and easily fixed.? The biggest thing I found was increased current draw as the components were stressed.

I tend to agree with Jerry.? Most of the time I encountered undervoltage issues, the symptoms were pretty obvious and easily fixed.? The biggest thing I found was increased current draw as the components were stressed.

This sort of issue comes into play when you try to design close to the limits.? When I first started learning electronics and so on, I would hear friends talk about a "fudge factor"... for instance designing circuits so that they exceeded tolerances by a significant amount, in order to deal with issues like undervoltage.? That's why the idea (mentioned earlier) of protective circuits is so important, but for most of the applications I've seen, the actual (vs theoretical/given) tolerances provide for a more robust and tolerant circuit.

Now that we're working with signals in the Ghz range and timing in the nanoseconds, these things should be in the back of a designer's mind, but at the same time there are other issues that need to be dealt with - like stray capacitance between traces and so on.? If your design is robust, the worst from a undervoltage would be temporary improper behavior.

Undervoltages can also sometimes be useful.? When trying to trash W10 on a hard drive so you can install Linux, sometimes you have to resort to something drastic to "kill" Windows.? It may be quick and dirty, but yanking the cord in the midst of saving something to the drive a few times is a good way to force W10 out of the picture - and then you can clean the drive and start fresh.

(GD&R!)
Bob
N4FBZ


On 5/6/21 1:49 PM, Jerry Gaffke via groups.io wrote:

I haven't been following the forum too closely, but we seem to have
hundreds of Nextion displays on uBitx's, and zero incidents
of Nextion displays getting blown by a low supply voltage.
So to all those with a Nextion, I'd say don't worry about it,
but be mindful of the possibility if voltage to the Nextion is below 4.75v.
This could be a Nextion design issue, not a CYA issue.

For pretty much any other electronics, don't worry about physical damage
due to undervoltage at all.? Just unexplained behavior.

Jerry, KE7ER


On Thu, May 6, 2021 at 10:36 AM, Arv Evans wrote:

??? Jerry
??? Yes.
??? On-line ham radio information is full of myths, conjecture, and
??? some outright
??? lies.? I suspect that you are correct about this being lawyer
??? instigated CYA
??? (Cover-Your_A$$).
??? Of course the original 1602 LCD display is not harmed by low voltage
??? operation.? If a Nextion is this easily damaged then that
??? manufacturer's
??? product probably should be avoided.? It might be interesting if
??? someone
??? with a variable voltage power supply and a few dollars to waste
??? could do
??? the necessary testing of that particular Nextion brand and publish
??? the results
??? so we could be aware of facts instead of having to rely on maybe
??? mythical
??? characteristics.
??? Arv

I haven't been following the forum too closely, but we seem to have
hundreds of Nextion displays on uBitx's, and zero incidents
of Nextion displays getting blown by a low supply voltage.
So to all those with a Nextion, I'd say don't worry about it,
but be mindful of the possibility if voltage to the Nextion is below 4.75v.
This could be a Nextion design issue, not a CYA issue.

For pretty much any other electronics, don't worry about physical damage
due to undervoltage at all.? Just unexplained behavior.

Jerry, KE7ER


On Thu, May 6, 2021 at 10:36 AM, Arv Evans wrote:

Jerry
Yes.
On-line ham radio information is full of myths, conjecture, and
some outright
lies.? I suspect that you are correct about this being lawyer
instigated CYA
(Cover-Your_A$$).
Of course the original 1602 LCD display is not harmed by low voltage
operation.? If a Nextion is this easily damaged then that
manufacturer's
product probably should be avoided.? It might be interesting if
someone
with a variable voltage power supply and a few dollars to waste
could do
the necessary testing of that particular Nextion brand and publish
the results
so we could be aware of facts instead of having to rely on maybe
mythical
characteristics.
Arv

Jerry

?

Yes.

?

On-line ham radio information is full of myths, conjecture, and some outright

lies.? I suspect that you are correct about this being lawyer instigated CYA

(Cover-Your_A$$).

?

Of course the original 1602 LCD display is not harmed by low voltage

operation.? If a Nextion is this easily damaged then that manufacturer's

product? probably should be avoided.? It might be interesting if someone

with a variable voltage power supply and a few dollars to waste could do

the necessary testing of that particular Nextion brand and publish the results

so we could be aware of facts instead of having to rely on maybe mythical

characteristics.

?

Arv