Grathio Labs of Steve Hoefer
Steve Hoefer, the main brain behind Grathio Labs. A freelance problem solver and writer. Active in the Open Source software and hardware.
Differential amplifier for HV Power Supply
This is part of a precision High Voltage but Low current Power Supply for Testing leakage currents in passive devices.
High Stability Reference Mirror
LM399 is a Precision Reference chip. From this a dual polarity mirrored reference is derived using OP07 op-amps. This assembly is mounted in a miniature oven to ensure temperature stability.
Homo sapiens to Homo Ludens
A long, long time ago a bright ape figured out that by climbing down from the trees he could more easily master his life, and that of others……Homo sapiens wanted something else, and better.
Digital Control for 8 Channel Analog Mux
A single Voltmeter or Digital Panel Meter DPM can monitor 8 Analog inputs from sensors or potentiometers using a Mux chip and creating simple digital controls for that.
Controlled Oven for stable Reference
This is a continuation of the previous two circuits. This circuit controls the temperature in a miniature oven that holds a stable dual voltage reference.
Optical obstacle switch with LM567
This is a simple toy that has many applications. Any object that breaks a light beam will trigger a relay to on condition for a period of time.
Universal Signal Conditioning Circuit
Here is a practical application of the dual differential amp. This circuit is for DC or slow moving DC like Strain Gauge and transducer signals.
16 Channel Analog Multiplexer
This circuit is built around the chip CD4067, now called 74HC4067, it works like a single pole 16 throw rotary switch that can be controlled digitally.
Low Cost AM FM Stereo Receiver
FM stereo demodulation is accomplished by the use of the LM1800 phase locked loop, thereby eliminating the need for external coils. The AM function of the receiver is done completely with the LM3820 AM radio system. While designed for 3 section tuned superheterodyne application.The LM382 dual preamplifier was selected for its minimum parts count and low noise capability.
DMM with ICL7103A and ICL8052A
The purpose of this application note is to describe the operation and potential pitfalls of a 10V resolution (VREF = 100mV) 4 1/2 digit autoranging scheme using the ICL7103A/ICL8052A pair. Two auto-ranging circuits are included within the text. Each is discussed in terms of its advantages and disadvantages.
Battery Operated Auto Ranging DVM
This application note describes a technique for auto-ranging a battery operated DVM suitable for panel meter applications. Also, circuit ideas will be presented for conductance and resistance measurement, 9V battery and 5V supply operations, and current measurement.
ATmega328 Single Board Computer SBC
The Atmel 8-bit AVR RISC-based microcontroller combines 32 KB ISP flash memory with read-while-write capabilities, 1 KB EEPROM, 2 KB SRAM, 23 general-purpose I/O lines, 32 general-purpose working registers, 3 flexible timer/counters with compare modes, internal and external interrupts, serial programmable USART, a byte-oriented 2-wire serial interface, SPI serial port, 6-channel 10-bit A/D converter...
Universal Signal Conditioning
Here is a practical application of the dual differential amp. This circuit is for DC or slow moving DC like Strain Gauge and transducer signals. The RC and Zeners are for protection and clamping. Why and how has been described in other posts here. The high impedance op-amp input cannot face the real world unprotected. OP07 is always the selection due to the low offset. When the sensor generates data in mV, you cannot afford any error introduced in this front end, right.
LM331 A to D Mux Input Switch
This is the full circuit of a V/F convertor interface for 80C31 SBC. The Mux is configured for selecting between two inputs. It uses analog switch 4066. LF353 along with LM331 form the VCO, you can further study such configuration in the Application Notes of TI/NS.
Two Stage Sequential Timer
This is an example of a cascaded or sequential timer, here two CD4541 are forming a two stage timer. You can add more in a chain, but better to use a microprocessor or Microcontroller for such a purpose. But make sure EMI-RFI immunity is high for these circuits or wrong resets and sets can make a machine like an Oven or Environment Chamber malfunction and even ruin the job.
Analog Blind Dial On Delay Timer
It is called analog dial timer as it has no digital display, but the chip is digital it is CD4541. It is Mains operated, you could make on-delay or off-delay. By changing the caps and resistors or with even dip-switches you could get timing of few seconds to many hours.
Battery Level Indicator
Battery level voltage measurement is best done with a dummy load. This circuit has four LEDs to show the charge left. It is important to avoid overcharge or deep discharge of rechargeable batteries. Never try recharging normal batteries. Using rechargeable batteries are good for the environment.
16 Channel Analog Multiplexer
This circuit is built around the chip CD4067, now called 74HC4067, it works like a single pole 16 throw rotary switch that can be controlled digitally. Clamping protection diodes are built in. Use resistors to enable this protection. 16 Analog channels are controlled by a Digital User Interface circuit made of 4093 and 4029. Up/Down and Auto/Man are four Push-buttons. A LED Display to show the Channel Number that is selected.
Synchronized Sample and Hold
This circuit has two analog mux 4051 operating in synchrony to store an analog value in a low leakage tantalum capacitor. This makes an Analog Memory possible and overall system accuracy of around 2%, which was more than adequate for this process. The analog value from a temperature transmitter is available for a short duration when it is collected from a rotating system with copper brushes and contacts on the shaft.