Continuity buzzer is frugal with power - 04/15/99 EDN-Design Ideas (contains several designs, scroll to find this one) The continuity detector in Figure 1 is based on W Dijkstra's "Fleapower circuit detects short circuits" (EDN, July 2, 1998, pg 122). The buzzer indicator allows you to devote full attention to making the connection without having to observe an LED. The circuit also consumes less power than Dijkstra's circuit. Power comes from two AA or AAA cells, which last for a period equal to their shelf life. Current consumption is less than 2.5 mA when the circuit detects continuity and less than 1.7 mA for an open circuit. Open-circuit voltage is less than 100 mV, and short-circuit current is less than 1 mA. __ Circuit Design by Hans Krobath, EEC, Nesconset, NY
Cuckoo-song Generator - This circuit generates a two-tone effect very much alike the cuckoo song. It can be used for door-bells or other purposes thanks to a built-in audio amplifier and loudspeaker Used as a sound effect generator it can be connected to external amplifiers, tape recorders etc. In this case, the built-in audio amplifier and loudspeaker may be omitted and the output taken across C8 and ground. __ Contact: Flavio Dellepiane, fladello @ tin.it
Curious C Beeper - The Curious C-Beeper uses the two-transistor flasher in conjunction with a darlington transistor to make a most unusual capacitance beeper probe. When a capacitor is touched to the probe, the probe beeps at a frequency that varies with capacitance. The frequency change __ Contact: Charles Wenzel of Wenzel Associates, Inc.
DC/DC converter operates from phone line - 01/15/98 EDN-Design Ideas DC/DC converters for use inside the telephone handset require operation from the high-source-impedance phone line. Additionally, the CCITT specifications call for maximum on-hook power consumption of 25 mA. The DC/DC converter in Figure 1 is 70%-efficient at an input power of 25 mA, providing 5V at 3.4 mA. Controlled, low-peak switch __ Circuit Design by Gary Shockey, Linear Technology Corp, Milpitas, CA
Destroyer Whooper Alarm - If you've ever watched any TV at all and seen those old WWII navy movies, you've heard that distinctive "whoop-whoop-whoop" as a destroyer sliced through the waves, guns blazing, and everybody yelling "battle stations!" __ Designed by Tony van Roon VA3AVR
Digital Game Show Timer - Several Game Show timers included, scroll to find this one. Using only two CMOS
IC packages, this game show buzzer performs well enough to be on TV! The first contestant to press his button locks out the other two contestants. The design is completely asynchronous and "fair". Other logic families will also work and any appropriate power supply is fine. For simplicity, a single-chime doorbell is used for the aural indicator. If a buzzer is preferred, use double pole pushbuttons with the second poles connected to activate the buzzer. Simply connecting a buzzer in place of the doorbell will work but the buzzer will sound until the reset switch is pushed. __ Contact: Charles Wenzel of Wenzel Associates, Inc.
Ding-Dong Bell - This simple and cost-effective door bell circuit is based on IC 8021-2 from Formox Semiconductors (Website address: fortech@mantramail. com). It is an 8-pin DIP IC whose only four pins, as shown __ Electronics Projects for You
Dinner is ready buzzer - How often on average do you have to call members of your family each day to tell them that dinner is ready, it’s time to leave, and the like? The person you want is usually in a different room, such as the hobby room or bedroom. A powerful buzzer in the room, combined with a pushbutton at the bottom of the stairs or in the kitchen, could be very handy in such situations __ Learning Electronics
Doggie Water Dispenser Alarm - I have two Beagle dogs. They drink a lot of water; they go through about 3 gallons a week. They have two water dispensers. One is on the inside and second unit on the outside of my house. Often, I forget to fill one of their two jugs and discover them completely empty. I do worry that my dogs might get dehydrated if I ever forget to fill both of their containers. . . Circuit by Dave Johnson P.E.-June, 2012
Door chime Privacy Sentry ATtiny12 - An ATtiny12 controller as a timer and some switching circuitry turns the doorbell off for 10 hours at the same time each day. __ Designed by Dick Cappels
Door Knob Alarm - Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms. A metal chain attached to a box holding the electronics is placed around the inside doorknob of a wood door. Anyone grabbing the knob from the outside is detected. . . Circuit by David Johnson P.E.-May, 2000
Door Knock Beeper - In some apartment buildings and homes, not equipped with a door bell, it may be hard to hear someone knocking on the front door. The circuit below provides a means to activate a loud beeping sound inside, whenever someone knocks on the door. . . Circuit by Dave Johnson P.E.-June, 2009
Doorbell for the Deaf - This circuit provides a delayed visual indication when a door bell switch is pressed. In addition, a DPDT switch can be moved from within the house which will light a lamp in the door bell switch. The lamp can illuminate the words "Please Wait" for anyone with walking difficulties __ Designed by Andy Collison
Doorbell heard in Basement - If you can't hear your doorbell when you are in your basement try this circuit. This circuit takes advantage of the 24vac power source located near the furnace. Using a simple current transformer technique, the circuit sounds a beeper whenever the . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000
Doorbell with Counter - This circuit uses a synthesized sound chip from Holtek, the HT-2811. This reproduces the sound of a "ding-dong" chiming doorbell. Additionally, the circuit includes a CMOS
4026 counter display driver IC to count your visitors __ Designed by Andy Collison
Electronic Buzzer - This very simple circuit just uses a couple of resistors, a capacitor and the easily available 555 timer IC. The 555 is setup as an astable multivibrator operating at a frequency of about 1kHz that produces a shrill noise when switched on. The frequency can be changed by varying the 10K resistor.
Electronic buzzer - This very simple circuit just uses a couple of resistors, a capacitor and the easily available 555 timer IC. The 555 is setup as an astable multivibrator operating at a frequency of about 1kHz that produces a shrill noise when switched on. The frequency can be changed by varying the 10K resistor __ Designed by Radioland.nt.au
Electronic Canary Doorbell - This circuit is a modified "Hartley Oscillator" with a couple extra parts. T1, the LT700 (Tony van Roon's or equivalent, is a small center tapped (Tony van Roon's ct) audio transformer with an impedance of 1000 ohms at 1000 hertz. The secondary of this transformer has an impedance of 8 ohms. Usually noted as 1K:8 ct. I tried a couple other models like the red and green types (Tony van Roon's taken out of a $5 made-in-china am pocket radio) and they both work good. You may have to adjust the caps to get the sound __ Designed by Tony van Roon VA3AVR
Electronic Chime - Scroll Down to find this circuit. This circuit simulates a chime similar to the sound many cars make when the keys are left in the ignition. The bottom two gates form a squarewave audio oscillator that drives the base of the 2N4401, turning it on and off at an audio rate. The top two gates produce a short low-going pulse about once per second that discharges the 10 uF capacitor through the diode. The voltage then jumps up and slowly decays __ Contact: Charles Wenzel of Wenzel Associates, Inc.
Electronic Police Siren - The sound produced imitates the rise and fall of an American police siren. When first switched on the 10u capacitors is discharged and both transistors. __ Designed by Ron J.
Emergency Siren Simulator - This siren circuit simulates police, fire or other emergency sirens that produce an up and down wail. __ Contact: Charles Wenzel of Wenzel Associates, Inc.