3 7v lithium battery full charge indicator circuit

FLASHING A LED circuit2

 

Music Reactive LED Chaser Light Circuit 12

 

7 Volt to 40 Volt Boost Converter 555 ic

 

VU Meter

 The Stereo VU Meter PC board with the components fitted. Only the battery and speaker are external, connected to flying leads. A close up of the completed unit. The overlay makes construction easy. Make sure the left-hand row of resistors starts with 47k at the bottom and 4k7 at the top. I saw one unit with the whole row reversed. It made very little difference to the performance of the unit, but it was not quite as sensitive as the correct version

The BOOTSTRAP circuit connects to the LED bar graph via A B C. Only one BOOTSTRAP circuit is provided on the board. It is capable of driving both bar graphs in a mono mode. For a stereo readout, you will need to build another bootstrap circuit. This will give a STEREO SOUND LEVEL INDICATOR.  

 

ROBOT-1 light-detecting circuits

 ROBOT-1 A simple robot can be made with 2 motors and two light-detecting circuits, (identical to the circuit above). The robot is attracted to light and when the light dependent resistor sees light its resistance decreases. This turns on the BC547 and also the BC557. The shaft of the motor has a rubber foot that contacts the ground and moves the robot. The two pots adjust the sensitivity of the LDRs. This kit is available from Velleman as kit number MK127.

PHONE TAPE

 PHONE TAPE - 2 The circuit is turned off when the phone line is 45v as the voltage divider made up of the 470k, 1M and 100k puts 3.5v on the base of the first BC557 transistor. If you are not able to get to cut the lead to the phone, the circuit above will record a conversation from an extension lead. The remote plug must be wired around the correct way for the motor to operate.

LED TORCH with 1.5v SUPPLY LED TORCH

 

LED TORCH with 1.5v SUPPLY This simple circuit will illuminate a super-bright white LED to full brightness with 28mA from a 1.5v cell. The LED is 20,000mcd (20cd @ 15° viewing angle) and has an output of approx 1lumen. The transformer is wound on a small ferrite slug 2.6mm dia and 6mm long. It is made from F29 ferrite material as the circuit operates at a high frequency (100kHz to 500kHz). The efficiency of the circuit revolves around the fact that a LED will produce a very high output when delivered pulses, but the overall current will be less than a steady DC current. BC 337 has a collector-emitter voltage of 45v. (BC338 has 25v collector-emitter voltage rating.) The voltage across the transistor is no more than 4v as the LED absorbs the spikes. Do not remove the LED as the spikes from the transformer will damage the transistor. The circuit will drive 1 or 2 while LEDs in series.