electronicsprojects(oldcompleted)

Electronics Projects

(Old & Completed)

Both Recent and Old Projects that have been Completed

• UPS With Solar And Mains Charging Capability, and 475 AH battery (also providing 12 volts DC for workbench and ham equipment)
• Calibrated Capacitor
• Dip Meter
• AF Oscillator
• Capacitance Meter
• QRP Wattmeter
• Signal Tracer
• Transistor Tester

- - GALLERY - -

Calibrated Capacitor

Everybody who builds equipment needs a "Calibrated Capacitor". This one is a 3-section unit with 500 pf in each section. The case is fiberglass, so there is minimal stray capacitance.

Dip Meter

The dip-meter dial is calibrated in pf, instead of frequency. A digital counter jack is provided so I can tell frequency by connecting a frequency counter. This has proven valuable when evaluating unknown inductors for frequency of oscillation and for amount of capacitance to achieve that resonance point.

AF Oscillator

This is the classic Op-amp (LM 1448) Wien-Bridge with #37 pilot lamp feedback element. Half the dual op-amp is the oscillator and the other half is the output buffer.

This C-meter was built from an old article in Popular Electronics from the 1970's era. I do not still have the article or schematic, but the circuit uses a CD-4001 as oscillator and integrates the output frequency to provide linear-scale meter readouts from around 2 pf to 1 mfd. Trim-pots were used to calibrate each range individually, hence unusually good accuracy.

QRP Wattmeter

This QRP Wattmeter has a pot instead of scale switching for various power levels. By marking settings on the pot rotation for various power ranges it allows convenient measurement of various power levels, from 7 mw FS up to 5W FS. In Hi-Z mode it functions as an RF voltmeter for peaking circuit tuning or as a Field Strength meter.

Signal Tracer

This signal tracer is just a dual op-amp (LM1458) followed by an LM380 AF PA stage to drive the speaker. Gain is extremely high (over 120 db) with around 1 megohm input impedance. That large (5 inch) speaker is the key to any really good signal tracer. You cannot hear subtle audio changes with a tiny 2 inch speaker, so use something with adequate size and frequency range.

Transistor Tester

This is the classic beta (DC gain) tester for evaluating transistors. It puts fixed current into the base and measures collector current. Nothing complex or fancy...it just works. Beta ranges are 0-100 and 0-500.

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Mains and Solar UPS

My UPS and station power system came about accidentally. The battery in my 10 year old computer UPS failed, so I replaced it with a car battery and added a solar charger to back up the UPS charger. Now I have emergency power from mains, solar, and battery sources. The 450 AH automotive battery sits just outside the hamshack wall with wires fed inside through a short section of 1/2 inch PVC electrical conduit. Not shown on the drawing is a set of government surplus aircraft type circuit breakers (purchased many years ago) that connect to 12 VDC outlets on the workbench and behind the ham station.

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