Strange digital clock dilemma

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dl324

Joined Mar 30, 2015
13,574
I was hoping to see a full schematic showing decoupling capacitors and the power supply wiring.
I think he posted that information in the posts I referenced. If not, he had another thread because I remember reading it. There are no decoupling caps on the IC's.
 

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Arjune

Joined Jan 6, 2018
176
Very kind of your DL 324 the display drivers are using cd4511s. My nature is not being acknowledged and I feel insecure.
 

dl324

Joined Mar 30, 2015
13,574
My nature is not being acknowledged and I feel insecure.
No offense intended. I haven't created a CD4511 component for the logic simulator I use. I have a subcircuit that has the decoder (which also supports hexadecimal) with the 7 segment display already wired to save me some work.
 

LesJones

Joined Jan 8, 2017
3,573
Thanks Dennis for providing the schematic of the power supply part that I was interested in. I can't see anything wrong with the design except the fact that there is no capacitor on the output of the 7805. One possible problem is that when the mains power is removed the transistor will still be enabling the displays until the voltage on the reservoir capacitor is close to zero. This means that the 9 volt battery will be trying to supply the display for a short time. If it is only a small battery such as a PP3 it's voltage may drop enough to cause a drop in the logic supply voltage. I think it might be worth adding a suitable voltage zener diode in series with the 10K base resistor and also adding a resistor between the base and emitter of the transistor.

Les.
 

Deleted member 115935

Joined Dec 31, 1969
0
Very kind of your DL 324 the display drivers are using cd4511s. My nature is not being acknowledged and I feel insecure.
Dont feel insecure @Arjune
we were all new at one point

Can you expand upon what you mean by "My nature"


We all try to give as much help to others, for free , in our own time as we can,
IMHO, It works best if the poster answers our questions as best they can,

As an example,
we have been asking for the complete schematic,
but you have not provided it,
leaving others to guess what you mean from old posts,

That does not make it easy for us to help you.
 

Deleted member 115935

Joined Dec 31, 1969
0
The power supply schematic was given in the first thread I referenced.

https://forum.allaboutcircuits.com/...ith-my-modulus-12-counter.168182/post-1516436

Copied here for convenience.
View attachment 246906

There are no pictures that show the wiring clearly.
What are C1 and C2 trying to do ?
where is the fuse ?
what is the voltage output of the transformer,
what is the voltage into the LDO
what current does the LDO supply ?

Why do you need 5v5 for the CMOS circuit you are driving ?

When the power is removed,
the transistor is still going to conduct till the C4 is discharged below 0.6 v.
The CMOS chips are still going to work , and the leds are still going to be drawing current,
At some point the LDO though will need to draw power from the battery.

The reverse is going to happen when you plug in the power.
Power ramp up is never monotonic,
its going to bounce, and during the bounce times, you are going, to be draining power off the battery to the leds,
and the leds drawing of a small 9v battery, is going to plummet the voltage , such that the CMOS will be unstable.

If you can post the complete circuit,
we will be able to help you with a sollution ,
 

Deleted member 115935

Joined Dec 31, 1969
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Baker Steve

Joined Feb 21, 2016
8
Several companies tried to use power lines for sending internet through your home in the late 1990s but that soon came to an end as everyone started using wiFi and realizing that mixing power lines and internet was a bad idea because the power protection for power line surges from lighting strikes or other surges can kill a motherboard pretty easily.
I appreciate that you are speaking about the US, and I don't know the situation over there, but internet-over-mains (for example Devolo) is still a thing in Europe. It's interesting that you mention X-10, as I have an extensive X-10 system here as wi-fi does not work well in buildings with granite internal walls. And I'm experiencing 'issues' with it despite a range of improvement measures. I am planning a mains interference analyzer to try to get to the bottom of it.
 

Baker Steve

Joined Feb 21, 2016
8
Decoupling capacitors work. They can't fix everything all the time, but they do fix a lot of things a lot of the time.
Sure do. I once worked for a guy that saved the military a couple of million for a redesign of a remotely-controllable target drone to make it EMP-proof. His solution: a $1 decoupling capacitor. I forget where it went, but it worked.
 

Deleted member 115935

Joined Dec 31, 1969
0
PDF's for those who don't want to install DesignSparkPCB.
WOW
thats going to take some following,
But thank you for making the pdf's of this ,

Each sheet seems stand alone,
with plugs / sockets on them
do we know from the other forums how these connect
 

Thread Starter

Arjune

Joined Jan 6, 2018
176
WOW
thats going to take some following,
But thank you for making the pdf's of this ,

Each sheet seems stand alone,
with plugs / sockets on them
do we know from the other forums how these connect
There are no plugs or sockets but the boards are connected with wires
 

Thread Starter

Arjune

Joined Jan 6, 2018
176
The time of the clock does not change when I plug and unplug its plug in the AC socket now but the time changes when I unplug my power amp out of the same power strip of the clock at Green hills adult home. I'm guessing but I think the power amp uses a transformer ((I'm thinking this is relevant information)). Maybe this has to do with the MOV in he power strip
 

Lo_volt

Joined Apr 3, 2014
235
I can't stress enough, even though many have already said it, put de-coupling caps on. At the very least put them on the 4510, 4511 and the 7555. These are the components most likely directly affected by power glitches.

DickCappels's suggestion to put a larger capacitor on the output of the voltage regulator is a good idea as well.

I don't think the capacitors across the AC line and neutral are going to do much, and I agree with DickCappels, they could make it dangerous.

You are doing great so far. From what you've told us, your clock is keeping time, your enclosure is simple but very workable. It's a great result for your project.
 

Thread Starter

Arjune

Joined Jan 6, 2018
176
This is my paranoia but I think maybe the ground of the electricity is isolated from Earth ground creating a voltage potential or some kind of spiritual potential even with the pipes of the building. If this is the case I have to use my reasoning to resolve the problem and then when I resolve the problem mentally a transfiguration will occur and maybe the clock will start functioning properly instead of blindly adding bypass capacitors because none of us know the problem for SURE. I really don't want to do anything in haste. If you choose to ignore me I don't blame you.
 

Thread Starter

Arjune

Joined Jan 6, 2018
176
What if I fused both 0.1 UF capacitors to ground instead of using one fuse for both, would it be safe then? I am worried about a neutral to live side short through both capacitor of the 12V power supply.
 
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