circuit harness wiring

There are systems in which it is imperative that the supply voltage of, say, a motor, always has the correct polarity. It is, of course, possible to use a bridge rectifier for this, but if large currents are involved, this is not always possible. This may be because large voltage drops across diodes result in appreciable heat dissipation, or that the peak current exceeds the current rating of a diode. Fortunately, a good, inexpensive mechanical rectifier may be constructed with the aid of a relay. In the diagram, the supply voltage is applied to K1, while the motor that needs a supply with correct polarity is linked to K2. Provided fuse F1 is intact, a positive potential at terminal a of K1 will be applied to the positive terminal of K2. Diode D2 prevents the relay being energized.

When the polarity at K1 is reversed, the relay will be energized via D2. The relay contacts then interchange the connections to the terminals of K2 to ensure that the previous polarity of the supply to the load is retained. Diode D1 is a freewheeling diode for the relay coil. The type of relay to be used depends on the requisite operating voltage and the current through its contacts. Other parts of the circuit are not critical. It stands to reason that the circuit is not suitable for use with a small battery, since the relay coil draws a fairly large current.

When a sensitive circuit must under no circumstances have too high a supply voltage applied, then some means of disconnecting the supply must be provided. One way to achieve this is to trigger a thyristor to blow a fuse. A less destructive alternative possibility is to use a MOSFET to disconnect the supply. An over-voltage protection IC, the LTC1696 from Linear Technology (www.linear-tech.com), has recently become available, which is suitable for triggering and driving such a device. It operates from a power supply in the range 2.7 V to 27 V and can be connected to the unregulated input of a voltage regulator. Two voltages can be monitored using feedback pins FB1 and FB2, suitably divided down using potential dividers.

The trigger threshold for both FB1 and FB2 is +0.88V. The value of the upper resistor in the potential divider can be calculated using the following formula: R1 = 33 kΩ× [(VLIMIT – 0.88 V)/0.88 V] The value of the capacitor connected to the TIMER/RESET pin sets the delay before the protection is triggered. The charging current for this capacitor depends non-linearly on the amount by which the voltage exceeds the threshold value. The greater the over-voltage, the faster the IC triggers. Once triggered the IC remains in that state until either the input voltage is removed or the internal latch is cleared using the MOSFET connected to the TIMER/RESET input.

We hope this circuit diagram will help you for your Christmas tree. This is not a difficult circuit but we do not recommend this for kids as it requires two voltages, 230 Volts and 9 Volts.  There are two ICs and one Diac do the major role in this circuits.

When you switch on the L1 bulb gradually increases its brightness. After it comes to the maximum brightness the bulb starts decrease the brightness gradually. This will never stop until you switch off the circuit as the cycle repeats.

You can change the brightness of the bulb by adjusting the VR1, but be careful when the circuit is connected to the live current. Make sure you use the same value and the ratings of the capacitor for the C3. Do not use low voltage of capacitor for it. The brightness of the bulb depends on the C3 capacitor’s charge and discharge.

Compact, transformer less circuitry No relays employed

Due to the low current drawing, the circuit can be supplied from 230Vac mains without a transformer. Supply voltage is reduced to 12Vdc by means of C1 reactance, a two diode rectifier cell D1 & D2 and Zener diode D3. IC1A, IC1B, R2, R3 and C3 form a reliable bounce-free toggle switch operated by P1. R4 and C4, wired to pin #6 of IC1B reset the circuit (lamp off) when power supply is applied. IC1C and IC1D wired in parallel act as a buffer, driving the Gate of the Triac through R5.

Circuit diagram:

 220V AC Lamp Toggle Switch Circuit Diagram

Parts:
R1 = 470R
R2 = 10K
R3 = 100K
R4 = 100K
R5 = 1K
C1 = 330nF-400V
C2 = 100uF-25V
C3 = 100nF-63V
C4 = 10uF-25V
D1 = 1N4007
D2 = 1N4007
D3 = BZX79C12
D4 = TIC206M
IC1 = 4011 NAND Gate

Notes:

• The circuit can be wired permanently to the mains supply as current drain is negligible.
• Due to transformerless design there is no heat generation.
• Low Gate-current Triacs are recommended.
• Obviously, other appliances can be powered in place of a lamp, provided their power dissipation does not exceed about 400W @ 230V
• 110-120Vac operation is easily obtained by simply changing C1 value to 680nF 250V. No further changes are necessary.
• In some cases, e.g. when the controlled device is far from the toggle switch, a pilot LED could be necessary for monitoring purposes. If so, disconnect pin #10 of IC1C from pin #11 of IC1D and wire a LED and its 1K series current limiting resistor across pin #10 of IC1C and negative supply.
• Warning! The circuit is connected to 230Vac mains, so some parts in the circuit board are subjected to lethal potential! Avoid touching the circuit when plugged in and enclose it in a plastic box.
• P1 will SPST Pushbutton

Source :www.extremecircuits.net