Digital Potentiometers(AD5204) The digital Potentiometers made by analog devices (AD5204) has 255 positions can be adjusted by the microcomputer that can receive commands from the computer. This is a great way for analog circuitry to have digital control. This is a chip with 4 digitally controlled POTs and the pots can be daisy chained to have multiple chips controlled by a single SPI interface.
Unlike a mechanical POT, digital POTs often have the restriction that one of the three terminals of the POT needs GND, making these devices harder to use in applications where none of the three terminals is GND -- such as LCD contrast adjustment, where the contrast is controlled by a voltage lower than GND.
|High current, Variable Voltage Regulator|
|These are 3.3V and 5V LDO, Low-Noise Voltage Regulators. Very small SOT-23 SMD package. 150mA max current. Best used in battery applications.|
Basic Voltage Regulators
|Variable voltage regulators, set output regulators, we give you the whole breakdown. Perfect for use with an external wall-wart power supply.|
The 723 Voltage Regulator
|Precision Voltage Regulator. Can be used as fixed or floating, variable, linear or switching.
NOTE: Only the DIP-14 version (image) has the Vz pin, which is used for negative regulators. The Metal Can and the Flat-Pack do not have enough pins so exclude the Vz.
|Extremely Efficient, 120mA Flyback Switching Regulators.|
See switching regulator.
Microcontrollers are little computers on a single Die/Package. The computer includes a CPU core, RAM, ROM/FLASH, and peripherals including UARTS, A/D converters, SPI, and I2C. Microcontrollers differ from microprocessors in that the microporcessors generally have bigger more powerful central processing units, but need support chips for ram, rom and other peripherals. Most modern microcontrollers use FLASH ram instead of a ROM so they can be programmed over and over. Many modern microcontrollers allow self-flashing to enable bootloading or a firmware update without pulling the chip from the circuit or using a programmer/debugger. Microcontrollers tend to be more optimizated for writting in assembly then PCs, but C and less so Basic are becoming the standard programming languages.
- LPC2103 Low cost 70MHz ARM7TDMI-S FLASH Microcontroller from Philips. The "$49" "Coridium ARMmite" does use this chip.
- Atmel AVR 8 bit FLASH microcontrollers
- Microchip PIC 8 bit FLASH microcontrollers
- Microchip dsPIC/PIC24 16 bit FLASH microcontrollers ( DsPIC30F 5011 Development Board )
- Microchip PIC32 32 bit FLASH microcontrollers
- Cypress PSoC 8 bit FLASH microcontrollers
- PIC Links A bunch of links to PIC based information.
- Main Page May have been a one man effort, now dropped. Has a bit of content that looks good.
Op amps and instrumentation amps.
An operational amplifier is one of the most useful of linear ( not digital ) circuits. It is normally a fairly low power device ( 15 volts 10 ma or less ) that can amplify, clip, offset.... op amps: great for amplifying weak signals from sensors to a more useful level. Also used in filters, integrators, etc. Very high gain differential amplifiers. Feedback through a resistor network is used to adjust final gain. Resistors and capacitors can be placed in the feedback path to create complex circuits such as filters. Often use it with a micro controller to “condition” signals from sensors prior to digitizing them. For example a temperature sensor may deliver 0 to 1 volt, where we want 0 to 5 volts for the PIC. The solution: a quick little op amp amplifier with a gain of 5.
- and on and on
See our main discussion at: op amp
Logic gates are the building blocks of digital circuits. Any digital circuit including microprocessors can be built out of the NOT function plus AND or OR.
Common forms found in discrete gates:
- NAND - NOT of an AND
- NOR - NOT of an OR
- XOR - exclusive or
- Flip-Flop - A 1 bit storage element that can be built out of more fundamental logic gates. Often available in packages of 8 and sold by the name of Latch or Register.
Descrete gates are available in a very large number of variations. The variations include TTL or CMOS inputs, standard vs. open collector outputs, and propagation delay.
- NAND gate: "Using a NAND Gate for a Set/Reset Latch" (the 74HC132 Schmitt-trigger quad NAND is better than the 74HC00 quad NAND).
- "Multiplexers: the tactical Nuke of Logic Design" by Dieter Mueller 2004 (74153)
There are hundreds of other specialized logic gates. Here we only list the ones we actually use in some Open Circuit Project:
- 74HC595 eight bit shift register with output latch (used for POV display)
- Low pin count( 8 - 12 ) microcontrollers are great for logic gate replacement when high speed is not required. Athough slower, slightly more expensive, and needing to be programmed they are great for prototyping due to the extra flexibility that comes from not needing to stock lots of gate variations.
- FPGAs are flexible ICs contain a very large number of gates( thousands to millions ) that can be arbitrarly connected together through programming in VHDL. Only available in surface mount large pin counts. It's possible to prototype processor designs with these devices.
RF modules allow transmission and reception of digital signals over radio. The two most common types are AM and FM( FSK ). The three major frequency bands used by unlicensed devices are 433MHz, 900MHz, and 2.4GHz. 433MHz has very limited uses by the FCC and is mostly used by garage door openers and wireless key entry systems. Many newer devices are moving to 2.4GHz due to the greater amount of room, althrough 2.4GHz is harder to use and has less range then the same power 900MHz system.
A major consideration when choosing an RF IC/Module is the amount of protocol stack that the device contains. Some modules are little more then a modulator and demodulator with the digial imput and output directly controlling the RF signal to serial line wire replacement modules that implement frequency hopping, pairing, error correct/detection, and retransmission of broken data.
Linx Technologies makes several low power RF transmitter/receiver chips. Their range is around 500' - 1000'. They are geared for one way communication only, like keyless entry systems. They also make several serial encoding chips that make the wireless communication more secure/crack proof. Their latest chip, the HS series, is based upon the SkipJack algorithm developed by the NSA. BBA broadband ampifier modules are available for boosting the signal power to 17dBm when combined with the HP-3 modules and FHSS techniques.
Xbee wireless module XBee/XBee Pro modules Modules are a drop in Zigbee module. Modules have a UART style interface with an AT command set. Cheap and very popular, these modules are great for serial cable replacement or remote sensor monitoring.
Sparkfun Bluetooth Module Dropin module with a complete Bluetooth stack. Modules also have a UART interface with a AT command set. An advantage is many laptops and cellphones have a Bluetooth transceiver builtin.
Nordic Modules from Sparkfun Tranceiver modules that have a SPI interface and are capable of transmitting packets at 1Mbps. Modules implement packet indentification and CRC checksum compution but don't have a protocol stack per say. A large number of channels are available making FHSS possible, but the modules has a maximum power of 0dBm making them only suitable for short range communication.
XE1205 Chip from Semtec Transceiver IC with builtin 15dBm power amplifer. IC has a SPI interface with the data being transmitted with any wire format(NRZ/Manchester). DP1205 dropin modules are available which contain all the necessary descrete components. IC allows very rich configuration including frequency down to 500Hz, frequency deviation, and baseband filter. Available in 433MHz and 900MHz versions.
Cypress Semiconductor makes several 2.4ghz transceiver modules, which are available for sampling, and are fully assembled with PCB antennas. They use SPI to be configured and to communicate with the microcontroller. The CYWM6934 (10 meter range) and CYWM6935 (50 meter range) are both very easy to interface with. ratmandu 20:06, 23 November 2007 (PST)
ADC analog to digital converter
There are a huge variety of ADCs available.
If you need 10 bits or less of resolution, counter-intuitively, it costs less to buy an ADC plus a microcontroller on one chip than to buy a stand-alone ADC.
- ATTINY13V -- lowest-price chip I know of with at least one 10 bit ADC
- ATTINY261 -- lowest $/ADC chip I know of
- LPC2101FBD48 -- lowest-price 32-bit microcontroller I know of with at least one internal 10 bit ADC
Many people (*) do EKGs with only 10 bit converters.
The Programmable Chip EEG might need more bits of resolution.
What low-cost ADC are available with at least 12 bits? (prices in quantity 1 from Newark or Digikey)
- $2.50 MCP3301 has 1 ADC input (13 bits)
- $3.50 MCP3302 has 2 ADC input (13 bits)
- $3.50 MCP3204 has 4 ADC input (12 bits)
- $4 MCP3208 has 8 ADC input (12 bits)
- $7 dsPIC30F 2011 microcontroller has 8 ADC inputs (12 bits). See dsPIC30F 5011 Development Board for details.
- $10 18F2553 USB microcontroller has 12bit ADC( $5.11 from http://buy.microchip.com in single unit quantities )
- $6.50 CY8C27443 Cypress PSoC microcontroller has 4 ADC inputs (14 bits) -- but what is the sampling rate? Also has 4 DAC outputs (9 bits).
- $56 analog devices AD7716: four independent, simultaneous 22 bit ADCs.
- the Maxim MAX1460 includes a 16-bit ADC, 12-bit DAC, a programmable gain amp (PGA), temp sensor, and 16-bit processor. (Alas, its program is in unchangeable ROM).
- Analog Devices AduC812: 200kHz 12-bit ADC, 12-bit DAC, and flash-based 8051 MCU core.
I am astonished to discover that (a few) microcontrollers include 12 bit or more ADCs. Are there others? --DavidCary 18:48, 28 August 2007 (PDT)