Multiple signals on single Serial TX line

the signal "TX"

time. On the secondary side the HF signal is caught by the advance of a ripple counter (4017). The clock rate is significantly higher than the TX rate and higher than the reset signal, so when the short time slice with many pulses occurs it will set O3 output high for long enough to charge the "OtherSig" capacitor.

idea? (I have looked at a microcontroller to decode the signal, but that takes to much current)

have sketched up quickly has too many parts.

See...

Uses noise removal gimmicks I first used for ignition systems... screened out the spark radiation into the pickup :-) ...Jim Thompson

I don't remember which one of the AD couplers it was but one client experienced major EMC issues with one of them. They used it for isolating an RS232 link. The noise pollution was in the VHF range and tough to filter out because on the isolated side we couldn't use much in terms of caps to ground because of agency certs and such.

Nothing there that a TVS plus maybe a TL431-style rail clamp couldn't handle :-)

Yes, but mostly we made our own transformers because of strict agency approvals that commercial vendors could not accommodate, or where they said it takes forever to get us "the papers". Also because I often need

that might just take care of the whole DC status restore. Only the first status after power-up is indeterminate, once you have sent the first transition it's "locked" into the correct signal polarity.

Coupled PCB inductors are another option if you slip a core through that. Such flat cores are now quite mainstream. But you need a controlled PCB fab process, usually with the proper certs and all that. So with all things considered this may not actually save money. I also have a hard time trusting those cores not leaving their work places in cases where the unit could take a hard fall.

Of course, whenever I can I use optocouplers because that is cheaper and often also smaller in footprint. They come in multi-packs as well.

For super high isolation there is also the McGyver method: LED and photodiode, plus a snippet of thin hose.

I used some of them (nine per board) that included the integrated, isolated, power supply. Passing the EMI tests was a piece of cake, probably because I was scared shitless of the 300MHz coming from the inverter, so took precautions. I was using it for an isolated RS422 link. I needed the isolated power to supply the RS422 drivers.

h 115kBaud

arrier

cted to the signal "TX"

hort time. On the secondary side the HF signal is caught by the advance of a ripple counter (4017). The clock rate is significantly higher than the TX rate and higher than the reset signal, so when the short time slice with m any pulses occurs it will set O3 output high for long enough to charge the "OtherSig" capacitor.

simpler idea? (I have looked at a microcontroller to decode the signal, but that takes to much current)

ones I have sketched up quickly has too many parts.

Very nice, thanks. I'll work further along this idea to check it out

Regards

Klaus

with 115kBaud

barrier

for

and

signal,

the

needs

Opto and using a transformer instead (the Pulse PH9185 is approved for the correct isolation and has the same area as the iCoupler)

Drivers can be directly from the microcontroller, using a high frequency PWM timer

frequencies with some filters to "decode" the signals and communication the other way could be a current modulation scheme or injection of a third frequency.

Yes. Could be a single pulse with restoration on the secondary side to recover the signal to save power.

Cheers

Klaus

We have had the same problem. AFAIR the problem was with the first versions of the Analog iCouplers, it has now been solved.

Yes, should be do-able.

Yes, that is certainly true. We need the approval anyway, since UL are going to look into other stuff.

Well, only for planar. If its coreless it can take the punishment from an elephant :-)

Cheers

Klaus

Would you Google groupies dump that shit and get a real newsserver/reader?! What a PITA!

timer

Microcontrollers take zero space, power, and cost?

frequencies with some filters to "decode" the signals and communication the other way could be a current modulation scheme or injection of a third frequency.

the signal to save power.

Using the same zero space, power, and cost microntroller, I presume.

A similar and even simpler solution has already been proposed. The OP has already rejected it as being unworkable.

Sorry, will get a new reader shortly :-)

timer

Yes, when we have one in there allready. (only on the primary side)

Cheers

Klaus

Thank you! ;-)

timer

How do you deal on the secondary? Smaller than a dual isolator?

the signal "TX"

time. On the secondary side the HF signal is caught by the advance of a ripple counter (4017). The clock rate is significantly higher than the TX rate and higher than the reset signal, so when the short time slice with many pulses occurs it will set O3 output high for long enough to charge the "OtherSig" capacitor.

idea? (I have looked at a microcontroller to decode the signal, but that takes to much current)

have sketched up quickly has too many parts.

Even simpler. See...

It occurred to me that the screen for Other_Sig could be used to blank the offending burble in TX_Output.

(I had no model for an analog switch... the VSwitch shown is 100 Ohms on, 10Meg off.) ...Jim Thompson

h 115kBaud

arrier

cted to the signal "TX"

hort time. On the secondary side the HF signal is caught by the advance of a ripple counter (4017). The clock rate is significantly higher than the TX rate and higher than the reset signal, so when the short time slice with m any pulses occurs it will set O3 output high for long enough to charge the "OtherSig" capacitor.

simpler idea? (I have looked at a microcontroller to decode the signal, but that takes to much current)

ones I have sketched up quickly has too many parts.

Reduces bost cost and occupied area, great :-)

Regards

Klaus

barrier

to the signal "TX"

time. On the secondary side the HF signal is caught by the advance of a ripple counter (4017). The clock rate is significantly higher than the TX rate and higher than the reset signal, so when the short time slice with many pulses occurs it will set O3 output high for long enough to charge the "OtherSig" capacitor.

simpler idea? (I have looked at a microcontroller to decode the signal, but that takes to much current)

I have sketched up quickly has too many parts.

Other thoughts:

(1) Use a tri-state device instead of an analog switch. (2) Trip retriggerable monostable on both rising and falling edges (I have that scheme around here somewhere... used it to delay a digital signal on both edges.) ...Jim Thompson

the signal "TX"

time. On the secondary side the HF signal is caught by the advance of a ripple counter (4017). The clock rate is significantly higher than the TX rate and higher than the reset signal, so when the short time slice with many pulses occurs it will set O3 output high for long enough to charge the "OtherSig" capacitor.

idea? (I have looked at a microcontroller to decode the signal, but that takes to much current)

have sketched up quickly has too many parts.

Best way, yet...

No filtering required, just timed sampling.

This has been fun. I enjoy "problems" like this... keeps the old brain turning over >:-} ...Jim Thompson

consumption may possibly be reduced.

immunity of 35kV/us. The PH9185 has 8pF capacitance from primary to secondary, so a dV/dt of this rate will inject more than 100mA into the rail of the primary side which could affect the communication related to how well the capacitance is coupled to the primary side and if it is symmetric coupled

and observations on the effects of common mode transients?

PCB xformer, although it needs to be subjected to a higher frequency to reduce magnetizing losses.

Concept check. How can there be magnetizing losses without a core to be magnetized?

?-)

magnetized?

Well, I suppose eddy currents in the windings will be lossy, and count as magnetizing (i.e., acts like a parallel impedance).

If you stretch the scope to include the system (so, the transformer and its driver), whatever handles the reactive current (capacitor or inverter) will also have some losses, and one could define "magnetizing losses" as that which is a direct result of the magnetizing current, and wouldn't have existed if the winding had very high inductance, as with a core.

Example: single transistor forward converter. When the switch is on, flux is stored in the transformer (while the load current is doing its thing). When the switch turns off, a source of restoring flux is required. Usually, the transformer's self inductance provides this; the flyback pulse is clamped, and the energy either dissipated (RCD peak snubber) or recycled (CT primary, one side switch, other side diode). Now consider what happens as the transformer's self inductance is dropped: load current remains constant, but magnetizing current rises, which puts more current into the flyback pulse. Flux is still conserved, but reactive power is much higher. You can see, if the inductance is so low that more magnetizing current is drawn than load current, the switch and diode must be beefed up significantly, and losses rise accordingly. It would be fair to attribute these losses to magnetizing, as long as one emphasizes that it's a system measure, not the transformer alone.

Tim

Isn't that the definition, that magnetizing current is the current that inherently must exist for a transformer to function? (so it does not matter if the core is present or not)

I'm working in low power these days, often the magnetizing current for those designs are higher than the reflected currents (secondary current)

Cheers

Klaus

Just make it a habit to only work on blustery days because then there is enough wind for some more power :-)

Core-less or "air core" look mostly just nice on paper. In reality ferrite often wins. Reason is that the leakage inductance is substantially higher without a core and also the required higher frequency leads to some other losses that add in. And for dessert there will usually be assorted EMC headaches.

I once contemplated using in-board (planar) coils for a particular inverter snubber circuit. But trying to do that while keeping the board profile less than gargantuan doesn't really make sense; add to that the difficulty of routing gate signals to said inverter around these loops!

Tim

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flux

thing).

current

must

fair

Wow, that would be a big stretch. Just the same down thread i read about adding cores, in that case it would make sense.

?-)