Translator
Touch controlled musical bell
Description.
Circuit diagram with Parts list.
Notes.
This circuit produces a musical tone
whenever someone touches the touch point designated as TP in the
circuit. The circuit works from two AA cells and produces enough sound.
The circuit uses IC UM 3481 commonly
used in musical circuits. The IC contains a ROM with 512 musical notes,
tone generator, rhythm generator, modulator, run off control,
oscillators, frequency divider and preamplifiers,. So a very few number
of components is required for this circuit.C1 and R1 act as the
timing components for the built in oscillator. The transistor Q1 is
used for driving the loud speaker. The base of the transistor Q2 is used
as the touch point to trigger the musical bell.
Notes.
- The circuit can be assembled on a general purpose PCB.
- Use two AA cells in series for powering the circuit.
- The speaker can be 2 W, 8 Ohm.
Latest Touch Alarm System circuit schematic
Touch Alarm circuit is widely used
for security, which is installed on the door. The advantages of this alarm is
because the cost is cheap and difficult to detect by burglars / intruders. The
following is an example of a touch of alarm circuit which is designed by Tony
Van Roon.
Components List:
R1 = 100K
R2 = 56K R3 = 10M R4 = 220K P1 = 100K D1 = 1N4004 |
T1 = 2N3904, or equivalent
U1 = 555 Timer* C1 = 47μF/16V** C2 = 33μF/16V** Re1 = Relay*** |
Notes:
*The
555 can be a LM, NE, or MC(cmos) type, they’re all pin-compatible.
**C1/C2′s
operating voltage should be elevated to 25V if you decide to go with a 12V
energy source. Rule of thumb: the operating voltage of capacitors are at least
double the supplied voltage, in other words, if the powersource is 9Volt, your
capacitor(s) is a minimum of 18V. Transistor T1 could be any approximate
substitute.
***
Use any suitable relay for the project and if you are not tight on area, use
any size. I’ve develop this specific circuit to prevent students from fiddling
using the security cameras in pc labs in the University I’m employed. I made
certain the metal casing was not grounded. But as the schematic shows you can
essentially hook it as much as any type of metal surface. I utilized a 12-vdc
power adapter. Use any appropriate relay to handle your requirements. A ‘RESET’
switch (Usually Closed) can be added between the constructive and the
‘arrow-with-the-+’. The trigger (touch) wire is connected to pin 2 of the 555
and will trigger the relay, utilizing the body resistance, when touched. It is
apparent that the ‘touching’ component has to be clean and can make good get in
touch with with the trigger wire. This particular circuit may not be suitable
for all applications. Just in case you wonder why pin 5 isn’t listed within the
schematic diagram; it isn’t truly required. In certain noisy conditions a
little ceramic capacitor is placed in between pin 5 and ground. It does no harm
to add one or leave it out.
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