Comments on: DIY Logic Probe

By: T1D

T1D — Thu, 03 Nov 2016 21:43:55 +0000

Hi, Keith, Thanks for the circuit! It appears that Pin #3/VCC has been omitted in the schematic(?) That might be a problem, for a novice. I am an Eagle user, but I have been playing with Fritzing, for this project. I would be glad to give you the files, if you would send me a pm with your email address.

By: Keith Neufeld

Keith Neufeld — Tue, 27 Nov 2012 01:03:34 +0000

Sam, that’s not super-easy to do with the LM339 comparator because of the open-collector outputs. What constraints do you have on your question? (For example, one answer is, “Buy a window comparator IC.”)

By: sam

sam — Thu, 22 Nov 2012 19:42:32 +0000

how would you light up an LED if the voltage is between 0.8 and 2.4?

By: Lucas

Lucas — Sun, 06 Mar 2011 19:07:26 +0000

Hey,

An electronics tutorial website that I frequent had a logic indicator built from a CMOS inverter, some resistors and some leds. I guess the circuit would not indicate a low level accurately, and a low level would include the “dead zone”. Would there be any way to combine the two designs to include multiple logic probes in one, or add a new feature using the CMOS, or TTL, inverter and your schematic? I was thinking about maybe chaining two inverters together for a low level.
The design is at: http://www.play-hookey.com/digital/experiments/logic_indicators.html.

By: Brad Gilbert

Brad Gilbert — Sat, 06 Dec 2008 03:13:34 +0000

It would be great if you could find a 1.6v regulator, then you wouldn’t be so dependent on the source voltage being 5v.

By: Daniel

Daniel — Fri, 30 Nov 2007 21:38:20 +0000

I built a logic probe similar but not exactly the same as yours, with plans from another site. Anyways what they did to deal with frequency signals was instead of how you used two separate LED’s they used a bi-color red/green LED. (or a red and green led wired in reverse parallel), anyways I believe if you used A bi-color LED in your circuit A signal You could have three separate outputs. Red = High, Green = Low, Orange = Frequency(sinusoidal, red green red green red green etc)