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LED Flasher Universal 3v - The electronic circuit below will flash any LED color with fixed current pulses powered by a 3v battery. It uses a charge pump approach, which routes a constant current pulse through the LED, regardless of the LED voltage requirement. Using this approach . . . Hobby Circuit designed
by Dave Johnson P.E.-June 22, 2008
LED Flasher-Wig/Wag - This simple circuit will flash two LEDs in an alternating fashion . . . Hobby Circuit designed
by Dave Johnson P.E.-December 18, 2004
LED Flasher-Wireless Circuit - When you would like to flash a LED through a thick plastic case without wires, use this hobby circuit. It performs this feat. It draws about 300ua of average current at 5v. It can be powered from a supply ranging from 3v to 6v . . . Hobby Circuit designed
by David A. Johnson P.E.-January 09, 2011
LED Lighthouse Flasher - This was originally designed
for a model in a HO train set. It simulates the behavior of the light from a lighthouse. The LED intensity gradually increases, then flashes with a bright light and finally decreases slowly in intensity . . . Hobby Circuit designed
by Dave Johnson P.E.-July 11, 2006
LED Lighthouse Flasher for HO Model Train - HO train sets often have authentic looking scale model homes and buildings. The hobby circuit below can be mounted inside a model lighthouse. The electronic circuit drives a single LED lamp in such a way that it produces light which simulates the rotation . . . Hobby Circuit designed
by Dave Johnson P.E.-July 11, 2006
LED Strings powered by AC Line - This shows 4 different ways to string white LEDs that are powered by a 120vac or 240vac power line. __ designed
by Ken Schultz, drawn Dave Johnson 12.18.2004-December 18, 2004
LED Test Signal Generator-40Khz - This 40KHz crystal controlled oscillator circuit drives an infrared LED with powerful 40ma pulses. The circuit can be used to test optical communications circuits, designed
to receive 40KHz modulated light signals . . . Hobby Circuit designed
by Dave Johnson P.E.-February 14, 2002
LED/Laser Light Output Intensity Meter - This circuit uses a large 1cm X 1cm silicon PIN photo diode and a transimpedance amplifier to measure the light power output of infrared and visible LEDs and laser diodes. It can be modified to produce almost any milliwatts to volts scale factor. It can b . . . Hobby Circuit designed
by Dave Johnson P.E.-July 08, 2000
LED_Light_8_Solar_Cell - I have been modifying a lot of solar garden and path lights for the last several years. I buy some units from home improvement stores, then I gut them completely. I take out the battery, electronic control board, LED and solar panel. I then replace those components with new units. I increase the size of the solar panel and battery. I use a more efficient and brighter LED . . . Hobby Circuit by David Johnson P.E.-September 22, 2017
LED_Light_for_Tool_Shed - I have a lean-to 8ft by 12ft shed next to my house. It is full of lawn chemicals and garden supplies. There were times when I needed to get something from inside the shed during the dead of night. Early on I had to use a flashlight. But later, I installed a series of five 12v LED light strips on the ceiling. Each strip contained 15 3v white LEDs. The strip had 5 strings of three LEDs, wired in series, with a 150 ohm current limiting resistor. . . . Hobby Circuit by David Johnson P.E.-July 14, 2017
Light Detector - This circuit uses a unique cascode amplifier circuit to convert the current from a PIN photo diode to a current without any feedback network. It is very stable and very sensitive. This hobby circuit shown has the potential for a conversion factor of 10 volts per microwatt at 900nm. I included a simple JFET post-amplifier with a gain of about 20. . . . Hobby Circuit designed
by David Johnson P.E.-March 12, 1999
Light Intensity Monitor - For an on-going consulting project, I had to determine the light output decay time of different fluorescent lamps. I wanted to know how fast the light from a lamp dropped to a low level, after current was interrupted in the lamp. I used a high voltage . . . Hobby Circuit designed
by David Johnson P.E.-April 01, 2005
Light Monitor Circuit - The circuit below takes advantage of a low power op amp with a “rail to rail” feature. The single resistor R1 defines the light sensitivity of the circuit. The output voltage is directly proportional to the intensity of light striking the small photodiode . . . Hobby Circuit designed
by David A. Johnson P.E.-September 01, 2010
Light Output Intensity Meter - This circuit uses a large 1cm X 1cm silicon PIN photo diode and a transimpedance amplifier to measure the light power output of infrared and visible LEDs and laser diodes. It can be modified to produce almost any milliwatts to volts scale factor. It can b . . . Hobby Circuit designed
by David A. Johnson P.E.-July 08, 2000
Light Pulse Receiver (2uS) - Although the LF357 is an obsolete part, this circuit gives you an idea how to build a sensitive modulated light detector with high ambient light immunity. The first section uses a 100mH inductor as an efficient photodiode current to voltage conversion circuit . . . Hobby Circuit designed
by David A. Johnson P.E.-June 03, 2002
Light Receiver 30Khz Amp - This circuit uses NPN darlington transistor to amplify the signal produced from short light flashes, as detected by a PIN photo diode. The circuit draws only about 330uA from a 6v battery . . . Hobby Circuit designed
by David Johnson P.E.-March 07, 2002
Light Receiver Amp-40Khz - This circuit is similar to 30KHZ LIGHT RECEIVER AMP but provides more gain and operates up to 40KHz. However it draws more power supply current. . . . Hobby Circuit designed
by David A. Johnson P.E.-March 07, 2002
Light Receiver Front-End Circuit - if you want even more sensitivity than the above circuit, try this design. When used with a one centimeter square photodiode, you can achieve a range of several hundred feet with a standard TV or VCR remote control module. Note: The LF357 operational amplifier is no longer available this circuit is for reference only. . . . Hobby Circuit designed
by David A. Johnson P.E.-March 12, 1999
Light Receiver-10MHz to 20MHz - Light power to volts conversion = APPROX. 15mV per microwatt at 850nM . . . Hobby Circuit designed
by David A. Johnson P.E.-July 11, 2006
Light to Frequency Converter - This circuit uses a CMOS version of the classic 555 timer, to form a light intensity to frequency converter. A small PIN photo diode is used as the light detector. The pulses produced are short, so in some applications you may want to stretch them or . . . Hobby Circuit designed
by Dave Johnson P.E.-August 31, 2006
Light, LED/Laser, Output Intensity Meter - This circuit uses a large 1cm X 1cm silicon PIN photo diode and a transimpedance amplifier to measure the light power output of infrared and visible LEDs and laser diodes. It can be modified to produce almost any milliwatts to volts scale factor. It can b . . . Hobby Circuit designed
by David Johnson P.E.-July 08, 2000
Light_Pathway_1w_Solar_Cob_LED - Chip on board (COB) LEDs are all the rage. These devices assemble multiple tiny LED chips onto a metal backed circuit board, then cover the assembly with a plastic cover. The metal back allows the assembly to be mounted to heat sink to keep the device cool. The multiple LED chips can be wired into any number of series/parallel configurations. Some are wired for 12v operation while other COB LEDs in flashlights are all wired in parallel, with an operating voltage of about 3 volts. . . . Hobby Circuit by David Johnson P.E.-May 23, 2017
Lighthouse LED Flasher - This was originally designed
for a model in a HO train set. It simulates the behavior of the light from a lighthouse. The LED intensity gradually increases, then flashes with a bright light and finally decreases slowly in intensity . . . Hobby Circuit designed
by Dave Johnson P.E.-July 11, 2006
Lighthouse_Solar_Powered - While at a discount store one day, I spotted an interesting tall lighthouse. It had a tiny solar panel and an equally tiny LED light. The LED was pointing downward, at the center of a rotating light reflector. I thought it might be turned into an interesting addition to my wife’s garden. . . . Hobby Circuit by David Johnson P.E.-September 21, 2017
Limiting Amplifier-40Khz - This circuit has a gain of X20 at 40KHz. The amplifier output level is limited to 2.5v peak to peak. Limiting action begins with a 50v peak to peak input . . . Hobby Circuit designed
by David Johnson P.E.-July 09, 2006
Line Powered High Intensity LED Flasher - There are times when you would like to generate an intensely bright flash of light using electrical power from the AC line. The circuit below can drive a one to three watt power LED with about 350ma of peak current. Since the circuit drives the LED with . . . Hobby Circuit designed
by David Johnson P.E.-December 07, 2008
Line Status Indicator for 1 Telephone Line - This circuit monitors one phone line . . . Hobby Circuit designed
by Dave Johnson P.E.-June 10, 2000
Lithium Battery Tester - I bought some lithium ion rechargeable batteries a while back. I was planning on using them to modify some solar powered LED spot lights. What I like about these new batteries is that they are the same size as a standard 1.5v alkaline AA cell . . . Hobby Circuit designed
by Dave Johnson P.E.-February 05, 2012
Lithium Ion Solar Battery Charger-#2 - A single lithium ion battery cell needs 4. 2v from a current source to insure it is fully charged. A solar panel with just enough individual cells wired in series to produce the needed voltage would be more efficient than one with more cells for a given surface area. if you divide 4. 2 by eight you come up with a figure of 0. 525 volts . . . Hobby Circuit designed
by Dave Johnson P.E.-May 21, 2013
LM317 adjustable voltage regulator used in Battery Eliminator Circuit - if you use a 1.5v or a 3v battery powered MP3 player for long periods of time, you may get tired of constantly changing batteries. Some older players do not work will NiMH rechargeable batteries so changing out batteries can get expensive. The circuit be . . . Hobby Circuit designed
by David A. Johnson P.E.-June 01, 2005
Locate a Plastic Pipe - I used this circuit once to track down the location of a plastic pipe, buried underground. It transmits a weak RF signal, which can be picked up by a portable AM radio from about 6 feet away . . . Hobby Circuit designed
by David A. Johnson P.E.-December 18, 2004
Low Current Flashing LED Power Indicator - This circuit flashes a power indicator LED to keep the average current low . . . Hobby Circuit designed
by Dave Johnson P.E.-June 04, 2000
Low Pass Filter, 3Khz, with an Audio Amp - This circuit uses a switched capacitor filter IC from National Semiconductor to filter signals with frequencies higher than the 3KHz needed for voice audio. The schematic includes an audio amplifier that is designed
to drive a standard audio head phone . . . Hobby Circuit designed
by Dave Johnson P.E.-June 04, 2000
Low Power 12,000 Volt Power Supply - if you need about 12, 000 volts DC for an ion generator this circuit might be the ticket. It draws power from the 120vac power line but it uses a small 6KV camera flash trigger coil. The output signal is isolated from the power line . . . Hobby Circuit designed
by David Johnson P.E.-March 27, 1999
Low Power LED Flasher - Judging from the numerous references I have received, this electronic circuit, hobby circuit seems to be rather popular. Many published circuits which flash LEDs need 3 or more volts. This electronic circuit uses only a single inexpensive C-MOS IC and . . . Hobby Circuit designed
by David A. Johnson P.E.-June 04, 2000
Low Power Sequential Flasher using 10 LEDs - A while back I posted a flasher circuit which flashed 10 LEDs sequentially. That circuit was powered by four AA alkaline cells. The circuit below operates much the same way but has been modified to run from a single 3v CR2032 lithium coin cell . . . Hobby Circuit designed
by David Johnson P.E.-April 17, 2011
Low Voltage Indicator for Lead-Acid Battery - Lead-acid batteries should not be discharged below a certain voltage. Discharging a cell below about 1. 8v and can often damage it, which will result in a lower amp-hour capacity. Large battery banks are critical in off-grid energy storage systems. One . . . Hobby Circuit designed
by David A. Johnson P.E.-July 30, 2006
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