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Comparing a "phase" at 3MHz

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Infraviolet:
Just to check about the 74hc4046:

A) where I don't need any of the VCO functionality I can take the inhibit pin high and the whole chip does nothing but provide the phase comparator?

B) it is possible to use the VCO parts of a 4046 for frequency generation applications entirely independently of what the phase comparator section is doing? Whilst the chip is marketed as a PLL, it can in practice be used as a single chip solution for generating a square wave output used for something entirely separate to the signals which the phase comparator part is processing?

Thanks

P.S. breadboard layout, mostly I'm not using wires on it, in many places the resistors run between the relevant holes, although Isuppose each side f the resistor is perhaps a 1.5cm wire. I've got each logically separate part of the circuit close together and only a very small numebr of longer wires between them. I produced some small PCBs which plug in to breadboard ends to provide power and ground to the side rails on both sides. For getting caps close to ICs, most of the ICs used here have Vcc and Gnd at opposite corner, I put one leg of each ceramic cap in Vcc, the other leg in the empty row "above" Vcc (imagine where pin 17 would be on a 16pin DIP), then run a cut section of 0.7mm solid core wire with striepdp ends directly from this row 17 down to the gnd pin, might be closer to 2cm for 16 pin chips actually, but not much more. Pin 16 of Vcc and row 17 for ground then take short 1cm jumper wires from their rows to power and ground rails on the right hand side of the IC. I think that phase shifting cap is doing enough to cure most of the noise spikes for now though. I looked over your refs, the scope probe accessory seemd mostly like a useful insulating cover to go over the probe spike and coiled springy grounding wire (this style i.stack.imgur.com/PSo3N.jpg) I'm presently using, I can see how it would make poking the probe in easier to avoid the risk of shorting nearby exposed resistor legs to ground when doing so. The list of prototyping methods seemed more aimed at what one does at the stage after breadboarding, rather than a substitute for it, the stage at which I go order first iteration PCBs. I was agreeing with your mentions of stripboard issues, but also pointing out that the other methods are all also based around soldering which isn't so practical when you're at the point of wanting to rapidly swap parts in and out for trial and error tweaking.

tggzzz:

--- Quote from: Infraviolet on June 23, 2023, 12:08:10 am ---I looked over your refs, the scope probe accessory seemd mostly like a useful insulating cover to go over the probe spike and coiled springy grounding wire (this style i.stack.imgur.com/PSo3N.jpg) I'm presently using, I can see how it would make poking the probe in easier to avoid the risk of shorting nearby exposed resistor legs to ground when doing so.

--- End quote ---

Electrically it is equivalent to the image you didn't show us. Sometimes mechanically the mechanism I made is more convenient, especially if the ground is further away. The main point was to illustrate the consequences of using a 6" lead.

With manhattan, it is easy to bend two pieces of wire (one for tip one for shield), solder them to the circuit, then insert/remove the probe as needed.



--- Quote ---The list of prototyping methods seemed more aimed at what one does at the stage after breadboarding, rather than a substitute for it, the stage at which I go order first iteration PCBs. I was agreeing with your mentions of stripboard issues, but also pointing out that the other methods are all also based around soldering which isn't so practical when you're at the point of wanting to rapidly swap parts in and out for trial and error tweaking.

--- End quote ---

Dead bug, rats nest and manhattan are suitable for breadboarding.

Soldering takes negligible time compared with design, collecting components, measuring results - and especially wondering whether your results are a consequence of your design or construction technique. I've seen far too many people chasing their tails over what turns out to be a problem with using solderless breadboards.

I prefer techniques that allow me to concentrate on my design's problems, rather than being misled by avoidable varying parasitic artefacts.

Terry Bites:

Here's a classic high speed zero crossing finder for a logic level signal:
You can find both edges of a pulse with an exor or xnor and a delay.
Use gates as non inverting delay. Delay from input edge to output rising edge and pluse width will depend on the propagation delay and rise time of the gates.
If needs be, you compensate for that with a small delay in the other channel.

Are you being denyed 10c RF transistors, are you being held prisoner somewhere. Can we help?

Infraviolet:
10c RF transistors, what type are you talking about? I can buy some if I knew some exmaple part numbers, but didn't know what they'd do better than the ones I've already got.

The 4046 seems a good solution now, if I wanted to use logic level chips I'd have to add in extra amplification stages before them, whereas with the 4046 I can feed straight from the low level analogue signal and perform the phase comparison from that. The 4046 does in one chip what would otherwise take multiple devices, even if I'm not using all its functionality.

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