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RPL1116 (MSO1000Z) and PLA2216 (MSO5000) Active Logic Probe teardown

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TK:

--- Quote from: dren.dk on April 03, 2019, 11:06:37 am ---The most important priority is that I build what I want, especially when the cost is basically zero.

--- End quote ---
I was just trying to comment on your design, as you made it public on this forum.  The idea of sharing something in eevblog is to get other's opinions, right?

TK:

--- Quote from: dren.dk on April 03, 2019, 11:06:37 am ---I see, good thing we didn't make it for you then.

Beside your personal preference, everything you said is just plain wrong:

0: If someone wanted to build one of these pods, then it would be very easy to leave out the offending parts and the space they take up was added to be able to have proper mounting holes, so there's no disadvantage to removing the option.
1: The LEDs show the current threshold voltage, so it's easy to notice if it has been set incorrectly, without digging down to the appropriate menu on the scope.
2: IOW: the LEDs do not show the power rails are there, but rather make critical information more readily available exactly where it's needed.
3: The added complexity is 2 extra BOM items (LEDs and micro controller, the resistors and the decoupling cap are the same as other items already used) in total it's 10 extra parts, the total number of parts on a pod is around 50.
4: Seeing as how the comparators dissipate enough power to reach 60 degrees, nobody is going to notice the  extra 10 mW taken by the microcontroller and a led.

Now, if I was building a mass-market product, then bean counters might force me to drop the reference-voltmeter option or start optimizing away decoupling caps, but as there is probably never going to be built in more than 5 of these sets, then cost optimization is not at all a priority.

The most important priority is that I build what I want, especially when the cost is basically zero.

--- End quote ---
Your eyes will be 90% looking at the scope anyways and not trying to look at some LEDs blinking on a sea of wires.  At least that is my experience debugging logic circuits.

dren.dk:
That's fair, I probably ended up sounding much more argumentative than I wanted, sorry if that was the case.

The point of the leds is not to blink out information, but to make it clear what the threshold is set at when I'm hooking up the probe, which is especially important and easy to miss if both pods are in use as the two groups of inputs have separate threshold voltages.

The state of the leds only change when changing the threshold voltage, so there should not be any need to stare at them or to get distracted.

TK:
Good points about the LEDs and the threshold settings :-+

oliv3r:
just make sure the leds are dimm enough to not be a distraction; using large resistors to reduce the current to 5mA may be just the solution :) Personally, I like the idea of the LEDS :)

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