Uni-Byte 0167 - Useful little Logic Probe Kit
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- เผยแพร่เมื่อ 9 มี.ค. 2024
- Fist in a series of 3 kit builds for you to enjoy while I'm away on vacation. This is a little Logic Probe. Not a tool I use all the time, but definitely a part of my mobile kit.
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This is where I got it - not affiliated.
Probe kit: mitchelectronics.co.uk/produc...
Instructions: mitchelectronics.co.uk/resour... - วิทยาศาสตร์และเทคโนโลยี
Thats a kit worth building.
Yeah, I like it when kits produce something useful.
I checked out the site and was impressed lots of info on the circuit, simulations and coloured build instructions. Loads of other kits....cheers.
YEs, they have some nice stuff - and fairly local to yourself!
Indeed ! :)@@uni-byte
Looks like the schematic I found
Are you going to build one up?
A long while back, I tried to design a logic probe. It was easier said than done. I was using a comparator to create voltage brackets. I forget the failure point and I can not find my computer project file. If I find that, I will post the issues. I do remember this... Many of these kits use a simple voltage divider to divide the sampled logic voltages in half. Then, the logic state is determined to be either higher, or lower, than this half-way voltage point, with the LEDs being illuminated accordingly. This is quite incorrect. The voltage points for TTL/CMOS/Etc. have an indeterminate zone in the middle of the voltage brackets. This dead zone must be correctly determined and displayed by the probe. Otherwise, a failure within the dead zone voltage range either will 1) not be discovered, or 2) be reported as operating correctly. I hope I find my file, because it is an interesting challenge to solve.
Oh, yeah x2... I think another challenge was that I was attempting to create an universal logic probe that would read both TTL and CMOS. Their bracketed voltage points are both based on percentages, IIRC... The low range maximum being 1/3 of the voltage and high range minimum being 2/3 of the voltage... Meaning, the voltage from 1/3 to 2/3 is indeterminate...
You could design it to switch between strictly TTL and CMOS levels. A lot of CMOS devices claim TTL compatibility but do not explicitly give there CMOS compatibility. Some strange hold over in standard engineering specs from the '70s and '80s. For instance, there are now "5V TTL compatible" memory chips that use 3.3V CMOS cores. The inputs are 5V tolerant and the outputs are TTL compliant, but they generally will not work in 5V CMOS environments because they cannot create the Vh sufficiently. Strangely only a few of the manufacturers mention "TTL only" in their spec sheets. A proper switchable probe would uncover this (as would a scope of course).
Lol. Chinese kits are better.
Some can be pretty hit and miss, but they are great for the detective types.