12V 15A Low Voltage Disconnect - The LVD1 kit is used for automatically controlling the power to 12V solar-powered battery-operated electronic devices. It shuts down power when the battery voltage drops to a selected voltage, protecting the battery from damaging excessive discharge conditions. Power is either automatically or manually reconnected at a selected voltage when the battery is recharged. An adjustable low-voltage indicator warns of the impending power outage. The low-voltage signal is externally available, allowing computers to monitor the condition and perform a graceful shutdown. The low-voltage signal can also be used for triggering a variety of low-voltage warning systems.
__ Designed by Solar Orbit Kit12V 20A Solar Charge Controller - The SCC3 kit is the heart of a 12 Volt solar power system, it regulates the charging of batteries from photovoltaic (PV) solar panels. A charge controller is an essential part of any solar power system. A 12 Volt solar power system can provide power to a wide variety of devices such as lighting systems, Ham and CB radios, car stereos, cell phone chargers, laptop computers, televisions, recording equipment, fans, water pumps and other 12V DC loads. With the addition of a DC to AC inverter, the DC power can be converted to 120 Volts AC for running many household electronic devices.
__ Designed by G. Forrest Cook
12V 9A Solar Power Center - The SPC3 kit contains all of the circuitry for a medium-sized solar power system. It includes a solar charge controller for battery charge regulation, a smart on/off power switch with automatic low voltage disconnect operation and a built-in white LED lighting system. Additional lights and other 12V devices can be connected to the load terminals and controlled by the SPC3. The SPC3 can regulate up to 9 amps of incoming solar power and can switch an external load of up to 10 amps. __ Designed by Solar Orbit Kit
12V LED Battery Voltage Monitor - The BVM1 kit can be used to monitor the voltage of a 12 Volt battery. It features ten ultra-bright LEDs in five vivid colors for quick battery voltage measurement. One of the LEDs will briefly blink on every 1.25 seconds, keeping average power consumption low. The display is readable from dark to full sunlight. A switch-controlled low voltage beeper is included, this provides a warning when the battery voltage drops below a preset value and can help to prevent excessive discharge. __ Designed by Solar Orbit Kit
12v Light/Dark Lamp Switch - At night, this circuit will route current to a 12v lamp, turning it on. . . Circuit by David A. Johnson P.E.-July, 2006
12v Touch Switch Exciter Circuit - This circuit is designed to generate a 20KHz pseudo sine wave signal that can power about 50 remote touch activated switch circuits. It can support a cable length of about 2500 feet. A typical remote switch circuit is also shown as well as a receiver circuit for those switches.. . . Circuit by David A. Johnson P.E.-February, 2002
12v-24v AC & DC Day/Night Switch - The circuit uses a bridge rectifier circuit to convert AC into DC. A 12v zener diode limits the operating voltage of the circuit to 12v. A tiny Schmitt trigger inverter and a phototransistor detects the ambient light intensity. If there is sufficient light, the inverter disables a push-pull oscillator circuit . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2012
1Khz to Over 70Mhz Light Receiver - This circuit uses one tiny C-MOS inverter IC to form a modulated light receiver with a very fast response. It is designed around a PIN photo diode that is packaged for use with plastic optical fibers. It can be used as an optical fiber receiver. By using the open end of the optical fiber it can "sniff" out any modulated light signals . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000
1us Light Pulse Receiver - This circuit is designed to detect very weak light pulses lasting 1uS. It uses a tuned LC feedback network to provide high sensitivity while giving high ambient light immunity. A post voltage amplifier is included with a gain of about X20 . . . Hobby Circuit designed by David A. Johnson P.E.-March, 1999
1uS Light Pulse Receiver + Post Amp - This circuit is designed to detect very weak light pulses lasting 1uS. It uses a tuned LC feedback network to provide high sensitivity while giving high ambient light immunity. A post voltage amplifier is included with a gain of about X20. The circuit is described in more detail in the receiver section of my Handbook of Optical Through the Air Communications. Note: The LF357 op amp is no longer available, this circuit is for reference only.. . . Circuit by David Johnson P.E.-March, 1999
1W White LED Night Light - As many of you know, I have a pet peeve with poorly made LED night lights. Often, the light from the LED quickly fades, so within months, the light is useless. I have posted several versions of modified night lights using higher quality components. This circuit is yet another version, which produces much more light than those other designs. . . . Hobby Circuit designed by David Johnson P.E.-November, 2008
20Mhz VCSEL 3mw Laser Test Circuit - This circuit takes advantage of some new vertical cavity surface emitting lasers (VCSEL) that don’t require light output control circuits. The circuit shows how to drive the device from a single high speed CMOS
IC. . . Circuit by David A. Johnson P.E.-June, 2000
24 Volt Day Night Switch - Many low voltage outdoor lighting systems use 24vac to power the devices. The low voltage is much safer to use outside than standard 120vac or 240vac power systems. The circuit below is designed to turn off power to outdoor lights during daylight and turn them back on at night . . . Hobby Circuit designed by David A. Johnson P.E.-December, 2010
24-Bit ADC Measures from DC to Daylight - DN219 Design Notes__ Linear Technology/Analog Devices
24v NiMH
Battery Charger using a 12v Solar Panel - A while back I received an email from a guy in the UK. He wanted to use a small solar panel, designed to charge 12v lead acid batteries, but use it to charge a 24v battery pack. His 24v battery pack used 20 AA size NiMH
cells. He went on to explain that his 20 cell NiMH
battery pack was used very infrequently . . . Hobby Circuit designed by David A. Johnson P.E.-October, 2011
2Mhz Broad Band Optical Fiber Receiver - If you need more sensitivity than the above circuit this circuit provides about ten times more gain. It too is designed around an inexpensive plastic optical fiber detector . . . Hobby Circuit designed by David Johnson P.E.-June, 2000
30Khz Light Receiver 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. . . Circuit by David Johnson P.E.-March, 2002
3mw Laser Test-20Mhz VCSE - L - This circuit takes advantage of some new vertical cavity surface emitting lasers (VCSEL) that don’t require light output control circuits. The circuit shows how to drive the device from a single high speed CMOS
IC . . . Hobby Circuit designed by David Johnson P.E.-June, 2000
4 in 1 Burglar Alarm - In this circuit, the alarm will be switched on under the following four different conditions: 1. When light falls on LDR1 (at the entry to the premises) .2. When light falling on LDR2 is obstructed.3. When door switches are opened or a wire is broken.4. When a handle is touched. The light dependent resistor LDR1 should be placed in darkness near the door lock or handle etc. If an intruder flashes his torch __ Designed by Radioland.nt.au
40Khz Burst Laser Diode Driver - Some laser tag or simulated combat games can use this circuit to send short bursts of modulated laser light at the opponent's vest, equipped with a matching light receiver. The circuit operates from three 1.5v cells (4.5v) that should provide enough energy . . . Hobby Circuit designed by David A. Johnson P.E.-June, 2000
40Khz Laser Burst Detector - This circuit was originally designed to detect weak flashed of laser light bounced off of a fabric video projection screen. It was used as part of a firearm training system. It generates a 100mS output pulse whenever it detects a 3ms to 5ms-laser burst,. . . Circuit by Dave Johnson P.E.-June, 2000
40Khz Light Detector with High Ambient Light Immunity - This circuit is designed for detecting infrared light modulated at around 40KHz. It’s feedback scheme cancels much of the DC component from ambient light. It’s conversion factor is about 100 millivolts per microwatt of 900nm light.. . . Circuit by Dave Johnson P.E.-July, 2006
40KHz Light Receiver Front-End Circuit - 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.. . . Circuit by David Johnson P.E.-June, 2000
40KHz Modulated Light Detector - 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. . . Circuit by Dave Johnson P.E.-March, 1999
40khz TV-VCR Light Source Repeater - This circuit is designed to be placed directly in front of a standard TV or VCR remote. The exiting light pulses produced by the circuit match the pulses from the remote but are about 10 times more powerful. Using the device, the remote can operate a TV or VCR over three times the normal distance. . . Circuit by David Johnson P.E.-June, 2000
50Mhz Broad Band Optical Fiber Receiver Version A - If the above circuit it still too slow, you can try this circuit. What it lacks in sensitivity it makes up for in speed. The circuit attaches a plastic fiber optic PIN photodiode assembly to a small box containing a small 3v battery and a standard. . . Circuit by David A. Johnson P.E.-June, 2000
5Mhz Broad Band Optical Fiber Receiver - This circuit is a simple broad band light detector that uses a very inexpensive IC and a PIN photodiode that is packaged for use with plastic optical fibers. It has a bandwidth from 1KHz to over 5MHz. It is great for experimenting with various modulated. . . Circuit by Dave Johnson P.E.-June, 2000
6V to 24V DC Day/Night Switch - Using an inexpensive phototransistor, this circuit switches 12v to 24v power to a load, whenever the sun goes down. . . Circuit by David Johnson P.E.-July, 2006
8-Solar Cell Lithium Ion Battery Charger Version 2 - Jim Wilber looked at my design for a battery charger and sent me some suggested changes. He suggested using the LTC4412 ideal diode IC to switch off the current path from the solar cell to the battery in darkness. He also noted that the 2.5v regulator from Seiko I had selected was no longer in production and suggested using the shunt reference. . . Circuit by David Johnson P.E.-May, 2013 |