12 Volt to 120 Volt Inverter

Ever needed a low power 120volt AC power source for your car, van or truck? Well this circuit should do the trick for you. It will supply 15 watts of AC power to a device. It should power lamps, shavers, small stereos and small appliances. If you draw to much power the circuit will shut down all by itself. The output of this circuit is a square wave so there may be some noticeable hum on audio units plugged into it. To reduce some of the hum increase the value of the output capacitor which is at .47uf now. That transistor in the circuit are high power PNP transistors. Radio Shack part number 276-2025 are good ones to use or TIP32. The transformer is a 24 volt 2 amp center tapped secondary Radio Shack part number 273-1512 or equivalent.

Thanks to:
http://home.maine.rr.com/randylinscott/project.htm

Touch 'N Flip

Ever wonder how a touch plate, like the kind you see on some elevators and lamps work? This circuit will give you a feel for how the touch plate works in a circuit and you can expand on the circuit to suit your project needs. The touch plate can be a small piece of metal or aluminum foil. Start the circuit by moving S2 to the set position and then back to the previous position. Now press S1. One of the LED's will light. Now touch the touch plate and the LED's will flip on the opposite way. The sensitivity of the plate will vary depending on the humidity. Adjust the VR and capacitor that is connected to S2 to adjust the sensitivity.

Thanks to:
http://home.maine.rr.com/randylinscott/project.htm

Guitar Tuning Aid

The basis of this circuit is the 555 timer operating in the astable mode. The oscillating output can be used as a tuning aid for a guitar. The first string of a guitar ,E, produces a frequency of 82.4 Hz. The frequency of the oscillator is set to twice this value, 164.8 Hz. and then followed by a dived by 2 stage to provide the required frequency. The purpose of the divide by 2 stage is to guarantee that the waveform produced has a duty cycle of 50%. The frequency of oscillation of the circuit is set by the adjustment of R1,R2 and C4. The output of IC2 is fed to the emitter follower Q1 to produce current gain to drive the speaker. C3 acts as a high pass filter to attenuate harmonics and produce a natural sounding note. The circuit is powered by 5 volt dc supply and this voltage must fall within the range of 4.74 to 5.25 volts for IC2 to operate properly.

Thanks to:
http://home.maine.rr.com/randylinscott/project.htm

Bike Light Flasher

I ride my bike allot at night and sometimes I'm not sure if people can see me. This circuit will flash an incandescent light that you can purchase from Radio Shack. Adjust the VR's for your flash requirements and make sure that the lamp you use is designed to put out high brightness. The enclosure should be water tight. The Batteries can be replaced by a bike wheel generator and a diode. If you add the generator then you can still use rechargeable batteries and the batteries will charge while you are riding your bike.

Thanks to:
http://home.maine.rr.com/randylinscott/project.htm

Voice Scrambler

With this circuit you can modify how your voice sounds by changing the pitch of your voice. This circuit can be connected to a phone and with a duplicate circuit on the end of the phone line, you can have a scrambled voice communication. The way the circuit works is as follows: If we cut the circuit in half at the T2 transformer and include the LM324 on the left side, you will see that the LM324 portion of the circuit is a tone oscillator which shifts the frequency of all input signals to a new higher frequency. When the voice and the tone oscillator mix frequencies the voice is not recognized. The voice signal is then inputted to the second stage which again shifts the voice signal again. I recommend that the first stage be tuned to a frequency that is 100hz lower then the second stage.

Thanks to:
http://home.maine.rr.com/randylinscott/project.htm

Touch Switch

This circuit uses a 555 timer as the bases of the touch switch. You can learn more about 555 timers in the Learning section on my site. When the plate is touched the 555 timer is triggered and the output on pin 3 goes high turning on the LED and the buzzer for a certain period of time. The time that the LED and the buzzer is on is based on the values of the capacitor and resistor connected to pin 6 & 7. The 10M resistor on pin 2 causes the the circuit to be very sensitive to the touch.

Thanks to:
http://home.maine.rr.com/randylinscott/project.htm

Signal Tracer

The main part of this circuit is the LM386 amplifier chip. It also uses a transistor input to buffer the input signal and provide extra gain for the LM386. The little unit has helped me out on numerous occasions when trouble shooting any amplifier circuit like a stereo receiver, tv / vcr audio section, radios, cd players and car stereos.

Thanks to:
http://home.maine.rr.com/randylinscott/project.htm