100W Transistored Inverter 12VDC to 220VAC

This inverter circuit can be used for medium electronic devices such as emergency light, radio, battery charger etc. Be carefull during assembly this circuit because of high voltage on the output transformer.

100W Inverter PCB Diagram:

100W Inverter PCB Design Layout:

Source of the circuit: 100W Interver Circuit

9V Mini FM Transmitter

The following diagram is the circuit diagram of 9V Mini FM Transmitter.

Schematic diagram:

Components List:

R1,R3 = 100K
R2 = 10K
R4 = 470 ohm
C1,C4 = 470pF
C2,C3 = 4.7µF/16V
C5,C6 = 4.7pF
C7 = 4-40pF trimmer cap (optional, see text)
L1 = 1µH
Q1,Q2 = 2N2222, NPN transistor
Mic = Electret Microphone
B1 = 9 Volt battery

Circuit Notes:
Absolutely nothing crucial here. To get a bit of tuning out of the coil you could put a 4-40pF trimmer capacitor (optional) parallel over the 1 µH coil, L1.

C1/C4 and C5/C6 are ceramic capacitors, preferably NPO (low noise) types. C2/C3 are electrolytic or can be tantalum kinds.

In the event you determine to substitute transistors with some thing similar you already have, it perhaps necessary adjust the collector voltage of Q1 by changing the value of R2 or R3 (simply because you alter transistors, it changes this bias on the base of Q1). It ought to be about 1/2 the supply voltage (about four or 5v).

The antenna is nothing more than a piece of 12" wire or a piece of piano wire from 6" to 12".

To find the signal on your regular FM Radio dial, make certain there's a signal coming into the microphone, otherwise the circuit will not function. I use an old mechanical alarm clock (you know, with those two big bells on it). I put this clock by the microphone which picks up the loud tick-tock. I'm certain you get the concept... Or you can just lightly tap the microphone whilst looking for the location of the signal on your receiver.

The antenna is nothing more than a piece of 12" wire or a piece of piano wire from 6" to 12".

To find the signal on your standard FM Radio dial, make sure there is a signal coming into the microphone, otherwise the circuit won't work. I use an old mechanical alarm clock (you know, with those two large bells on it). I put this clock by the microphone which picks up the loud tick-tock. I'm sure you get the idea... Or you can just lightly tap the microphone while searching for the location of the signal on your receiver.

Source: http://www.sentex.ca/~mec1995/circ/fmt4.html
Design by Tony van Roon

Touch Activated Alarm

This is a touch activated alarm system. Your alarm system will be activated when someone touching the "trigger". You may use this circuit at your home door, your vehicle etc.

Parts 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 working voltage ought to be elevated to 25V in the event you decide to go with a 12V power source. Rule of thumb: the operating voltage of capacitors are at least double the supplied voltage, in other words, if the power source is 9 Volt, your capacitor(s) is a minimum of 18V. Transistor T1 could be any approximate substitute.

*** Use any appropriate relay for the project and if you're not tight on area, use any size. I've build this specific circuit to prevent students from fiddling using the security cameras in pc labs at the University I'm employed. I made sure the metal casing was not grounded. But as being the schematic shows you are able to essentially hook it as much as any type of metal surface. I utilized a 12-vdc power supply. Use any suitable relay to deal with your specifications. A 'RESET' switch (Normally Closed) can be added between the constructive and also the 'arrow-with-the-+'. The trigger (touch) wire is connected to pin 2 of the 555 and will trigger the relay, using the body resistance, when touched. It is apparent that the 'touching' component has to be clean and can make good contact using the trigger wire. This particular circuit might not be suitable for all applications. Just in case you wonder why pin 5 is not listed within the schematic diagram; it is not really required. In particular noisy circumstances a little ceramic capacitor is placed between pin 5 and ground. It will no harm to put one or leave it out.

Additional note: For those of you who didn't discover, there's an approximate 5-second delay build-in before activation of the relay to avoid false triggering, or perhaps a 'would-be' thief, and so on.

Circuit design by Tony van Roon.