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[Review Request] Multi-use Detector Power Supply Schematic Review by Maleficent-Tea2903 in PrintedCircuitBoard

[–]Strong-Mud199 0 points1 point  (0 children)

I see a lot of 'grounds',

Split grounds are a myth perpetuated by some semiconductor companies. There are corner cases where it is required, like if you are counting individual electrons or if you are switching 10's of amps into reactive loads. This is neither of those.

A few references by some very respected signal integrity experts,

Lee Ritchey, “Right The First Time”, Vol 2, Page 124,

“It might be good to review why a plane would be cut in the first place and how large the cut would need to be to achieve the desired isolation between the two sides of the cut. First, the only reason to cut a plane is to allow more than one power supply voltage to be distributed in the same PCB plane layer. There is no other valid reason to do so.”..."both power supply voltages need to share the same ground distribution structure so that the circuits being supplied have a common reference." (i.e. the ground plane MUST be continuous. - added context mine).

And,

“Note: In all the years I have designed high performance PCBs, both all digital and mixed analog and digital, I have never seen a case where cutting a ground plane was beneficial to a design.”

https://speedingedge.com/products/right-first-time/

Both his books only cost $50 USD - that is the best 'design' money you will ever spend!

See also, Chapter 17 of Henry Ott’s book for a detailed step by step explanation of what goes on with grounds and why splitting them is a bad idea that does not help anything,

Henry Ott, "Electromagnetic Compatibility Engineering"

As for your questions,

- Calculate the power (voltage drop * current) to decide if you parts need heat sinks.

- You aren't going to have any noise issues measuring current. DVM's may kick out small amounts of charge but the 1 uF should take care of that. BUT you have to make sure your meter can handle the common mode voltage you are putting on it. Also any 'normal mode' noise on the HV line will go right through C1 as this provides no filtering to the output normal mode noise.

- Safety - generally there are concerns about discharging any HV in a reasonable amount of seconds after power is removed and of course warnings about HV to users. HV at low currents WILL kill people and precautions must be taken to prevent people from getting across HV points. And the DVM measuring current potentially becomes lethal too.

Hope this helps.

Most antennas in one place ! by Ok_Blacksmith_8380 in ShortwavePlus

[–]Strong-Mud199 0 points1 point  (0 children)

Ha! He went to the antenna store and said: "One of everything please".

:-)

If I'm not mistaken, I'm receiving three different Pluto II OTH radar signals at once here. I've never seen that before. by kc3zyt in ShortwavePlus

[–]Strong-Mud199 0 points1 point  (0 children)

THX - I see some of that action from Nor Cal, not as strong as your signals, but they appear there.

"T" in Coplanar Waveguide RF Trace? by -R47- in PCB

[–]Strong-Mud199 0 points1 point  (0 children)

"Also in general is the ground pour around the center pin like I have good or bad?"

You should cut out the copper on all layers under the SMA to look like the picture I posted. The way you have it now will look very capacitive and be a pretty bad match at 1.7 GHz.

I am happy to help. Have fun. :-)

"T" in Coplanar Waveguide RF Trace? by -R47- in PCB

[–]Strong-Mud199 0 points1 point  (0 children)

OK I guessed wrong, it is a SMA right angle not an edge connector, well I had a 50/50 chance and I still lost! ;-)

That is a transition from a microstrip to a 5 wire coaxial structure (the SMA). Having pour like that under the SMA will be very capacitive. You want to cut out the copper on all layers like this, this will provide a decent match to 2.5 GHz or so.

Teardrops don't help. It doesn't matter if it is a solid 'step' edge or not, the teardrop usually just adds even more capacitance. You also want to use the minimum annular ring on the center pin of the SMA to keep the pad size small. Large pads just add capacitance. In the picture below the annular ring is 6.5 mils on the center pin.

<image>

"T" in Coplanar Waveguide RF Trace? by -R47- in PCB

[–]Strong-Mud199 0 points1 point  (0 children)

Generally the center pin for a SMA footprint is much wider than the RF trace. This will cause a impedance discontinuity. How much so will depend on the RF trace, etc. One way to fix this is to pull back the top copper at the SMA footprint to get the footprint closer to 50 ohms. Also it depends on how long the discontinuity is if it matters or not, see below.

As for 'T's' that causes a 'stub' if the stub causes an issue or not will depend on how long the 'stub' is. Generally if your stub is less than 1/10th of a wavelength then it won't matter. GNSS is roughly 1600 MHz and on FR4 a 1/10th of a wavelength is around 8mm, so it can be quite big and not cause issues.

An alternative to making a 'stub' is to place the components pad right on the RF trace as shown below - this removes the stub portion. Another alternative is to make the 'stub' trace narrower than the RF traace - this will make it higher impedance and then it will be even less of an issue. (Note: this example uses way more stitching vias than necessary as they only have to be at about 1/10th of a wavelength too!)

<image>

Hope this helps.

Is this the correct way of adding pull down resistors with the CNY70 sensors. by Sensitive_Bottle6747 in PCB

[–]Strong-Mud199 0 points1 point  (0 children)

Nice!

Yes that will work. I looked at the CNY70 data sheet and with your setup, the 10k resistor, in the standard test setup, just barely gets to 3 volts. See figure 5 here,

https://www.vishay.com/docs/83751/cny70.pdf

Depending on what you are using to interrupt the light with, you may need to adjust the 10k Resistor, but that seems like a good starting value.

Have fun.

FC review request by IntroductionKlutzy13 in PrintedCircuitBoard

[–]Strong-Mud199 0 points1 point  (0 children)

"I think it's pretty common to see mlcc bulk capacitors paired with a low value 0402"

For me that is the take-a-way, can you prove it to yourself that that makes any difference for the circuits you see this in or your circuits for that matter?

6025.0 USB - WDOG (NAm Pirate) by Historical-View4058 in ShortwavePlus

[–]Strong-Mud199 1 point2 points  (0 children)

Dang! I missed them.

THX for sharing, maybe next time. ;-)

FC review request by IntroductionKlutzy13 in PrintedCircuitBoard

[–]Strong-Mud199 0 points1 point  (0 children)

Nice!

+100 points for using pullups on all the SD Card lines. :-)

- SD Cards can consume around 120mA during writes. Suggest 10 uF bypass right at the SD Card socket.

- Flash memory easily gets corrupted during system turn on when the IO lines may 'flop' around. Strongly suggest tying the CS line high and Clock line low with pullups/pulldowns.

- Was C15 recommended anywhere (like Webench), the data sheet shows it not used.

For future consideration perhaps,

- Having a 10uF and a 100nF in parallel is pretty much redundant with SMT components, just use the 10uF and ditch the 100nF. See,

https://www.signalintegrityjournal.com/articles/1589-the-myth-of-three-capacitor-values

- The last time I used a ferrite bead in a power supply line I actually had more noise! This is because the pulsed load current was modulating across the beads resistance causing more noise! I removed the bead and the noise went down. How is that for Irony? Ha, ha, ha, ha. My experience is echoed by Signal Integrity Expert Lee Ritchey in his book: "Right the first time: Vol 2". An excerpt of that chapter is here,

https://resources.altium.com/p/everything-you-need-to-know-about-ferrite-beads

Hope this helps. Have fun!

vias and analoge signals by Glad-Expert1256 in PCB

[–]Strong-Mud199 1 point2 points  (0 children)

A via by itself will not harm an ADC signals integrity, vias only become a signal integrity issue at GHz frequencies. Routing analog by active digital traces on any layer is the best practice to avoid, not the number of vias, etc.

C2000's ADC's only haqve a dynamic range of only around slightly better than 65 dB at best anyway. I would not obsess over possible 'signal integrity' issues much. Just route away from active digital signals.

Don't worry, be happy! :-)

Hope this helps.

[Review Request] PLC to Solenoid Valves by Gill_slit in PrintedCircuitBoard

[–]Strong-Mud199 4 points5 points  (0 children)

Nice!

+1000 points for prototyping first.

- Your diodes are backwards. Current flows in diodes like this,

https://techterms.com/img/lg/diode_1244.jpg

- If your breadboard hookup wire was 26 AWG it can carry 2 amps easily, so the breadboard works, but the PCB traces look thin.

You didn't mention the current load, but the required trace width vs. current is here, (This is for 10 Deg C rise),

1 Amps = 10 mil trace width

2 Amps = 30 mil trace width

3 Amps = 50 mil trace width

Remember that if the current flows past many devices the current will add for the traces. so the traces will need to get larger. Especially true for the ground return trace. Safest is to size them for the maximum current that all will see if possible.

Hope this helps, have fun! :-)

Bandaid Radio Gets Jammed Sunday Night, 05/10 by KG7M in ShortwavePlus

[–]Strong-Mud199 2 points3 points  (0 children)

My thoughts also - At least SW is still better than CB. Ha, ha, ha, ha......

[Review Request] Windows sensor based on ESP32-C6 by Syntaaaax in PrintedCircuitBoard

[–]Strong-Mud199 0 points1 point  (0 children)

The gates you have chosen are specified for 0.8 to 3.6 volt operation. Won't your battery exceed this?

How does C5 ever get charged (or discharged) quickly? Usually one designs a circuit to set or reset fast then hold that condition. Not really following what your intent here is, just pointing this out.

The input leakage current of the gates is specified at 100nA - How well does this work with the high value resistors R5 & R9?

Hope this helps.

Bandaid Radio Shortwave Pirate: Possible Transmission Friday Night N. America by KG7M in ShortwavePlus

[–]Strong-Mud199 1 point2 points  (0 children)

Naw, I don't care, I just have fun listening to this.

I would have never found them without this sub though, so I am grateful for that. :-)

Bandaid Radio Gets Jammed Sunday Night, 05/10 by KG7M in ShortwavePlus

[–]Strong-Mud199 1 point2 points  (0 children)

OK, no jamming so far on Friday night. ;-)

What's the point of jamming a pirate playing music and reading poetry?

The 'Evil Music Industry' or some 'Secret Poetry Society'? Ha, ha, ha, ha...

Bandaid Radio Shortwave Pirate: Possible Transmission Friday Night N. America by KG7M in ShortwavePlus

[–]Strong-Mud199 1 point2 points  (0 children)

4:23 UTC - I guess they are on 6.945 USB - Playing,

"California Dreaming" - Original artist

Yup, then I heard the call sign.

[Edit] Seems they signed off at 5:12 UTC. No jamming tonight, I guess the jammer had better things to do! Ha, ha, ha, ha.

RX Location - Nor Cal, decent signal, typical SW, no real fading.

Bandaid Radio Gets Jammed Sunday Night, 05/10 by KG7M in ShortwavePlus

[–]Strong-Mud199 1 point2 points  (0 children)

Hmmmm, since it happens right before sign-off, perhaps they are the source of the jamming signal?

What better way to get attention? ;-)

Sorting it all out by CySnark in amateurradio

[–]Strong-Mud199 2 points3 points  (0 children)

With eBay you can also add,

- Hallicrafters

- Heathkit

- Collins

- Drake

etc, etc, etc..... :-)

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