Hey, actually figured something out on my own! (zero-crossing detector)

[Zero999]

I dont know why unhelpful? I suggested upthread that you just feed a bridge rectifier waveform into the AoE circuit and it's job done...

In fairness it's not as simple as taking the output from the bridge rectifier and connecting it to the AoE circuit. Note D1 & D2 and R6 & R7 in my circuit.

[Xena E]

I dont know why unhelpful? I suggested upthread that you just feed a bridge rectifier waveform into the AoE circuit and it's job done...

In fairness it's not as simple as taking the output from the bridge rectifier and connecting it to the AoE circuit. Note D1 & D2 and R6 & R7 in my circuit.

Regards,
X.

[Zero999]

The only addition is a diode that isolates the bridge rectifier from the subsequent reservoir capacitor, however the basic circuit will work as I describe.

Like this?

 Zero cross bridge rectifier diode drop.asc (3.29 kB - downloaded 9 times.)

That's the part I wanted to avoid, because it introduces an additional voltage drop.

Another option is to use two bridge rectifiers, with eliminates the additional diode drop. There are always several ways to solve the problem.

 Zero cross 2 bridge rectifiers.asc (4 kB - downloaded 9 times.)

[Xena E]

The only addition is a diode that isolates the bridge rectifier from the subsequent reservoir capacitor, however the basic circuit will work as I describe.

Like this?
(Attachment Link)
(Attachment Link)

That's the part I wanted to avoid, because it introduces an additional voltage drop.

Another option is to use two bridge rectifiers, with eliminates the additional diode drop. There are always several ways to solve the problem.
(Attachment Link)
(Attachment Link)

Thank you!

Yes, (almost) exactly. I messed up putting the circuit in the previous post, but it's there now, just lost the body of text, (no loss).

The diode drop being a problem would depend on application. IME no real problem as theres usually headroom for the ubiquitous regulators anyhow.

X

[Circlotron]

The only addition is a diode that isolates the bridge rectifier from the subsequent reservoir capacitor, however the basic circuit will work as I describe.

Like this?
(Attachment Link)
(Attachment Link)

That's the part I wanted to avoid, because it introduces an additional voltage drop.

Another option is to use two bridge rectifiers, with eliminates the additional diode drop. There are always several ways to solve the problem.
(Attachment Link)
(Attachment Link)

In the second circuit with two bridges, D2 and D4 are unnecessary.

[Zero999]

The only addition is a diode that isolates the bridge rectifier from the subsequent reservoir capacitor, however the basic circuit will work as I describe.

Like this?
(Attachment Link)
(Attachment Link)

That's the part I wanted to avoid, because it introduces an additional voltage drop.

Another option is to use two bridge rectifiers, with eliminates the additional diode drop. There are always several ways to solve the problem.
(Attachment Link)
(Attachment Link)

In the second circuit with two bridges, D2 and D4 are unnecessary.

That's true, as they're in parallel with D6 & D8. When I drew the schematic, I assumed D1 to D4 and D5 to D8 are bridge rectifier ICs, not discrete components. I suppose you could go for a high power bridge rectifier for D1 to D4, skip D6 & D8 and use low power diodes for D5 & D7.

I also forgot the hysteresis resistor.

For completeness here's the schematic and simulation.

[Xena E]

The only addition is a diode that isolates the bridge rectifier from the subsequent reservoir capacitor, however the basic circuit will work as I describe.

Like this?
(Attachment Link)
(Attachment Link)

That's the part I wanted to avoid, because it introduces an additional voltage drop.

Another option is to use two bridge rectifiers, with eliminates the additional diode drop. There are always several ways to solve the problem.
(Attachment Link)
(Attachment Link)

In the second circuit with two bridges, D2 and D4 are unnecessary.

That's true, as they're in parallel with D6 & D8. When I drew the schematic, I assumed D1 to D4 and D5 to D8 are bridge rectifier ICs, not discrete components. I suppose you could go for a high power bridge rectifier for D1 to D4, skip D6 & D8 and use low power diodes for D5 & D7.

I also forgot the hysteresis resistor.

For completeness here's the schematic and simulation.
(Attachment Link)

Very good, thank you.

The advantage of the scheme is that in the conjuction a fast enough diode type is used in the position of D5/D7 of your circuit, the input frequency that can be sampled giving a directly proportional output pulse that is then only likely to be limited by the slew rate of the comparator, overcoming the problems associated with a fixed pulse period, as in Tooki's scenario of the Aircraft 400Hz system, or slow rectifier diodes.

In other words, in higher frequency applications, don't use 1Nx400X series rectifiers.

X

[RJSV]

   The classic case, using logic, could just be implemented in discrete parts.
In the classic edge detect, your logical AND will have a direct input, that maybe just came up, (to a logical 'one', and that is paired with a slightly delayed copy.
   With this,  you've got a window of a short time,  (and also thru an inverter), so that the opportunity is short,  and, soon that logical 'and' function won't have both inputs in the correct form (that is, both logical 'one').
 
   But a rising edge will make it through that, for the short time, before the AND gate stops.
Of course,  you will need to do that in logical equivalents, when using discrete parts, including the negative Boolean logic, where a logical 'OR' will act as a 'negative logic' AND gate.

   That means that a zero with a zero will satisfy the AND, in negative logic sense.