131 articles written by Jim Keith

Author: Jim Keith

About: I grew up in Massachusetts. I cut my teeth on electrical cord and learned how not to splice such by age 7. Started building my first hobby circuits at age 11 using the venerable 1N34A diode & 2N107 transistor. In high school, I knew more than the teacher so I taught my physics class electronics--LOL. Still too dumb to get into MIT, I attended Wentworth Institute of Technology (where MIT dropouts also go) and then Moody Bible Institute. However, most of what I learned was not in school. I eat, drink and sleep circuits--repeatedly, have I awoken with a circuit solution. The electronics industry has provided good employment throughout my career and now retired, I continue with hobby stuff and a small ebay electronics business. The photo is that of Toby, my grandaughters' beagle.


555 Propagation Delay Oscillator Schematic

555 Propagation Delay Oscillator

Jim Keith - 01/19/2016

With no external components, a 555 can be turned into an oscillator that runs typically in the range [...]
555 Schmitt Trigger Logic Inverter Level Translator

Versatile 555 Schmitt Trigger /Logic Inverter /Level Translator

Jim Keith - 12/13/2015

More undocumented applications for the 555 ‘oscillator:’ Not all applications oscillate as we will see. Most are knowledgeable [...]
Input Offset Voltage Test Schematic

Test Op Amps Via Simple Input Offset Voltage Measurement

Jim Keith - 10/04/2015

Measuring this one vital parameter (Input Offset Voltage) provides a simple means of determining if the DUT (Device [...]
Single Pushbutton Latching Relay Engine Start Circuit

Single Pushbutton Latching Relay Engine Start Circuit

Jim Keith - 10/03/2015

Small engines often have two pushbuttons: A start pushbutton to operate the starter motor and a stop pushbutton [...]
Static Reversing 3 Phase SSS Schematic

Static Reversing the 3 Phase Induction Motor

Jim Keith - 09/27/2015

This solid-state thyristor (SCR) switch circuit is perhaps the simplest means of reversing a 3 phase motor. “Static” [...]
Dehumidifier Hack Schematic

Dehumidifier Hack

Jim Keith - 08/02/2015

What does one do when the electronic control of a modern dehumidifier goes south? Simple; gut the electronics [...]
Noise Hardened Linear DC Signal Opto Isolator Schematic

Noise Hardening for the Industrial Environment, Part 2

Jim Keith - 03/30/2015

In my experience, the most difficult problems encountered involved electronic circuit boards that were sensitive to industrial EMP [...]
Motorcycle Battery Level Indicator

Motorcycle Battery Level Indicator

Jim Keith - 03/24/2015

This battery level indicator offers (2) incandescent lamps that light up progressively as the voltage increases. It is [...]
Industrial Run-Stop Relay Circuit With Snubber

Noise Hardening for the Industrial Environment, Part 1

Jim Keith - 03/23/2015

Application of linear and digital ICs in the industrial environment has its own set of nasty problems. Circuits [...]
Linear DC Signal Opto Isolator Schematic

Linear DC Signal Opto Isolator

Jim Keith - 03/21/2015

This simple circuit provides better than 1% accuracy in optically coupling a DC voltage signal. To compensate for [...]