Update (05/07/12)

• Added a TRF Broadcast radio receiver using a loop antenna and 5 transistors. Similar to a crystal radio with an audio amp. Located in the Analog/RF section.

Update (04/04/12)

• Added a couple window comparator circuits in the Analog/RF section. One monitors temperature in a 10 degree range, and the other monitors light level within some range using a LDR.

Additions and corrections (11/24/11)

• LED Fader circuit using a PIC controller and 1/2 watt LEDs. Listed in LED section. "PIC Controlled Fading Eyes"

Additions and corrections (10/05/11)

• Buck Converter (1 watt LED driver) from 12 volt battery. Listed in power circuits section.

Additions and corrections (06/09/11)

• Solar Array Boost Converter Battery Charger. Listed in power circuits section.

Additions and corrections (01/01/11)

• Three examples of low frequency Wien Bridge RC sinewave oscillators listed in the analog/RF section. Also added a link to LTSpice, useful for circuit simulation.

Additions and corrections (08/24/09)

• IR Receiver Toggle Switch - Responds to hand held remote controls. Listed in relay circuits section.

Additions and corrections (02/11/09)

• Autodialer security system calls your cell phone when switch is closed. Listed in telephone circuits section.
• Dual 1.5 volt LED flasher runs one year on 'D' cell. LED section.
• Automobile interior lamp fader, listed in power section.
• Quartz crystal synchronizer for mechanical clock, analog/RF section.
• Removed a few bad links and reorganized external link section.

Additions and corrections (11/01/07)

• Added another PIC clock timer circuit. This one controls 4 timed outputs that can be programmed from 1 minute to 1 week. Located in the LED section.
• Added another lamp fader circuit to control automotive interior lights. Located in Misc section.
• Added a loop antenna for use with small AM radios.

Additions and corrections (07/07/07)

• Added a superhet AM broadcast receiver to the Analog section. The AM superhet receiver covers the broadcast band from 540 Khz to 1650 Khz. The circuit employs the 8 pin Signetics balanced mixer IC (NE602) which converts the incoming RF signal to the standard 455 Khz IF signal and provides about 13dB gain. The IF signal is amplified by a single transistor stage and audio is recovered using a biased shotkey diode (5082) and JFET buffer transistor. The LM386 audio amp is used to drive a small 2.5 inch speaker at about 200 milliwatts.

Additions and corrections (12/05/06)

• Replaced the PIC Digital Clock Timer with a better version. Much easier to use with less parts. Includes calendar with leap year correction and also daylight savings time corrections using the new system in effect next year.
• Added another relay toggle circuit using a single 555 timer. It uses one more resistor than the 556 version, but takes less space to build.

Additions and corrections (07/10/06)

• Added new circuit "Sunrise Lamp" to slowly brighten a 60 watt 120VAC lamp over a 20 minute period when power is applied. Circuit is located in the Power circuits section. Also updated the "Fading Red Eyes" circuit in the LED section to include parts list and construction details using a solderless breadboard. This project has been recently published in the online magazine "Design News" and can be viewed at www.designnews.com in the Gadget Freak section, case #86.

Additions and corrections (09/27/05)

• Added new circuit "Relay Toggle Circuit Using a Dual 555 timer (556)" in the relay section, and also a 2 cell lithium battery charger (7.5 volt) in the power section.

Additions and corrections (06/25/05)

• Added an improved 3 transistor audio amp in the analog section.
• Added a 18 stage LED sequencer using 2 cascaded 4017 decade counters.
• Added a new link for datasheets.

Additions and corrections (01/08/05)

• Added new circuit "PIC Digital Clock Timer" in the LED section. The clock timer uses a PIC16F628 microcontroller to display digital time and control an external load. Timer output duration can be programmed from 1 to 59 minutes and can be manually switched on and off. Assembly code included.

Additions and corrections (12/04/03)

• Added new circuit "8 Stage LED VU Meter" in the LED section
• Added new circuit "Sunset Lamp", in the power section, which slowly fades out a 12 volt light over 1.5 hour period.
• Added a couple links in the commercial section to LED sites selling high power Luxeon LEDs, 12,000 mcd white LEDs, and very bright colored LEDs (red, blue and green).

Additions and corrections (08/10/03)

• Updated the Resistor color code calculator so it shows equivalent 5% and 1% values for 2 known values entered.
• Updated the "Game Show Who's First Indicator" to use low gate current SCRs so that smaller wattage resistors can be used.
• Updated the "Ignition Coil Buzz Box" circuit to reduce part count.
• Added a link in the educational section to a PIC microcontroller tutorial site which I found very informative. I just did my first PIC project using the 16F628 to sequence a few lights. You can buy these things on e-bay for about $2.68. The PIC16F628 has 2K of program memory and can be flash programmed 100 times or more. PIC Microcontroller Tutorial

Additions and corrections (06/02/03)

• Added a new circuit in the analog/RF section to measure sound pressure level. It's called "LED Decibel Meter" but also drives small incandescent lamps with an extra transistor.

Additions and corrections (01/30/01)

• Added a new circuit in the relay section to toggle a relay using a single mosfet and 4 resistors and a capacitor.
• Updated some obsolete links

Additions and corrections (01/06/06)

• Added a new circuit in the LED section to sequence up to 100 LEDs, or small Xmas lights using a couple 4017 decade counters as a 10x10 Matrix.