This would have helped me early on in the electrical endeavors, so I wish to share them with others.
Attached is schematics to wire logical circuits (like OR, AND, NAND, NOR, XOR). Most of these have been tested on a bread board or at least in Spice. Please tell me about any errors or ways to make better circuits. This hopefully is a work in progress and maybe other useful circuits will make their way on here. Most of the circuits I have created on my own, but a couple I have found from various places on the net.
Generally speaking, a "better" circuit (ones I would like to hear about) would mean less parts, or same number of parts but using less power or are more TTL compatible.
This document contains schematics to make logic gates from discrete components.
The top row is the “Signal” version of the circuits. These are useful for interfacing the output with high-impedance inputs. Most have a weak pull up (10K-ohm) for a logic high and are open-drain when logic low.
The bottom row is the “Power” version of the circuits. These are useful for powering components or interfacing with other TTL or high-impedance input devices (a pull-down resistor should be added to outputs in these case). Most do not have any pull resistor on the output, but will be a high output when logic high, and become high-impedance when logic low. Note that power will back-feed through the P-channel MOSFETs if voltage is applied to output and none is applied to INPUT of the circuit.
The schematics have INPUT symbols. If above the INPUT symbol there is an “INV” the voltage applied here must be the same as IN's logic high. If there is no text, any voltage can be applied as long as it is compatible with the transistors used.
Most of the schematics in the black boxes have TTL-compatible IN's. Also contained in the document is red boxes with alternate wiring options. These are usually simpler, but may not be compatible with TTL other devices.
Note that most of the circuits will view no input on the IN as a logic low, but not all will.
The advantage of these circuits over prefabricated ICs (besides the obvious educational values) is the option to interface different voltage components with each other. Though the resistor values may need changing if you aren't using the recommended 2.8V-6V range, the majority of these circuits can accept inputs or output at greatly varying voltages.
April, 2008: when I discovered the answers to all my micro-computational-botherations!
Some of my objects:
MCP3X0X ADC Driver - Programmable Schmitt inputs, frequency reading, and more!
Simple Propeller-based Database - Making life easier and more readable for all your EEPROM storage needs.
String Manipulation Library - Don't allow strings to be the bane of the Propeller, bend them to your will!
Fast Inter-Propeller Comm - Fast communication between two propellers (1.37MB/s @100MHz)!