Impossible Enterprises -- Octal Logic Probe V1.1 Kit

Octal Logic Probe V1.1 Kit

Especially when proto-typing with single chip computers like the PIC, SX, etc. it is often necessary to determine if multiple outputs are correct. So I created this, an octal logic probe that can be plugged directly into a proto-typing socket to view eight adjacent pins at once. Several can be used to monitor the complete chip. Don’t worry if one or two pins are analog or even tri-state, this probe wont mind and it wont affect your application either.

This is the version 1.1 kit. It includes the following:

	2	LM2901 Quad Voltage Comparators
	9	1K ¼W 5% resistors
	9	T¾ Green LEDs
	1	Printed Circuit Board
	1	8 Pin Header 0.1" spacing
	1	2ft cable with RCA Plug

This is version 1.1 of the kit which is adapted to the LED voltage reference by extending one led lead and soldering it to the trace on the top side of the board. This is what was used for the images in the instructions.

Download and read the instructions for more details on how to construct an octal logic probe.

Here's a ZIP file with the the schematic and board design files.

ALERT! Jameco no longer carries the MV50G [SKU 176532] Green T¾ LEDs. I'll be searching for more, but for now I only have a few sets left. I'll be contemplating making some design changes for version 2 to accommodate substitute LEDs.

From just a physical examination it looks like any 2mm x 5mm rectangular LED will fit, tightly, but fit. And perhaps a 3mm round LED for the voltage reference. You might check at Futurlec for some posibilities. I have not confirmed the voltage drop, so make sure you do.

Now for all you folk who are willing to wait for version 2.2; I need some feedback. Send me some mail telling me what you want.

2mm x 5mm rectangular LEDs — They pack well, but make the probe thicker,
3mm round LEDs — They would take up the entire top of the board leaving little or no gap between the nibbles [clumps of four bits],
A complete surface mount kit,
A fully-assembled surface mount probe, OR
Another suggestion.

And of course e-mail me if you find another source for those little green LEDs.

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