Toggle Switch | Electronic Project Circuits

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220Vac Lamp Toggle Switch

Compact, transformerless 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.

Parts:
R1____________470R 1/2W Resistor
R2_____________10K 1/4W Resistor
R3,R4_________100K 1/4W Resistors
R5______________1K 1/4W Resistor
C1____________330nF 400V Polyester Capacitor
C2____________100µF 25V Electrolytic Capacitor
C3____________100nF 63V Polyester or Ceramic Capacitor
C4_____________10µF 25V Electrolytic Capacitor
D1,D2________1N4007 1000V 1A Diodes
D3_________BZX79C12 12V 500mW Zener Diode
D4__________TIC206M 600V 4A TRIAC
IC1____________4011 Quad 2 Input NAND Gate CMos IC
P1_____________SPST Pushbutton

Be the first to comment - What do you think? Posted by admin - February 19, 2011 at 6:35 am

Categories: Electronic Control Tags: lamp control circuit, toggle switch, triac circuit

High Current MOSFET Toggle Switch with Debounced Push Button.

This circuit was adapted from the “Toggle Switch Debounced Pushbutton” by John Lundgren. It is particularly useful in controlling a load from several locations where the load may be switched on from one location and switched off from another. Any number of momentary (N/O) switches or push buttons may be connected in parallel. The circuit uses a N-channel power MOSFET to control the load and can supply fairly large currents depending on the MOSFET used. The IRFZ44 is a 50 amp device available at Radio Shack for $2.99 and the IRF10 is a 4 amp device available for a dollar less.

The combination (10K, 10uF and diode) on the left side of the schematic insures the circuit powers on with the MOSFET turned off and the NPN transistor conducting. These components can be omitted if the initial power-on condition is not a concern. In this initial state (MOSFET off), the voltage at the gate of the MOSFET will be near zero and the voltage on the 1uF capacitor connected to the switches will also be near zero.

When a switch is closed, the 1uF capacitor is connected to the junction of the 220 ohm and 470K resistors causing the voltage to fall to near zero turning off the NPN transistor. As the transistor turns off, the collector voltage rises and turns on the MOSFET when the voltage climbs above about 3 volts. The drain terminal (D) of the MOSFET now moves close to ground preventing the NPN transistor from turning back on. When the switch is opened, the 1uF cap will charge through the 1M and 10K resistors to the full supply voltage. When a switch is again closed, the 1uF capacitor will cause the NPN transistor to turn back on due to the positive voltage on the capacitor applied to the junction of the two resistors (470K, 220). The MOSFET will now turn off and the drain voltage will rise to the supply voltage which in turn keeps the NPN transistor conducting with a positive voltage on the base. The circuit has now returned to the initial turn-on state.

The small (0.1uF) capacitor connected from the transistor base to ground functions to filter out noise that could cause false triggering if the switches are located far away from the circuit using long wires. If false triggering becomes a problem, either the capacitor value (0.1) or the 220 ohm resistor value can be increased to provide better filtering. Increasing these values however will increase the switching times of the MOSFET (rise and fall times) generating more heat when the MOSFET changes state. This is probably not a problem with small loads of a couple amps or less, but may be a problem at higher load currents. The circuit was tested at 1.5 amps using the IRF510 and 6 amps using the IRFZ44.

From : http://ourworld.compuserve.com/homepages/Bill_Bowden/

Be the first to comment - What do you think? Posted by admin - April 24, 2007 at 10:27 am

Categories: Basic electronics, Electronic Control Tags: circuit switches, power mosfet control, toggle switch

Relay Toggle Circuit Using a 556 Timer

This toggle circuit operates by using a couple 555 timers wired as inverters. Pins 2 and 6 are the threshold and trigger inputs to the first timer and pin 5 is the output. The output at pin 5 will always be the inverse of the input at pins 2 and 6. Likewise, the output at pin 9 of the second timer will always be the inverse of the input at pins 8 and 12. A 100K resistor connects the output of one inverter to the input of the other so the state of one will be the opposite of the other.

In operation, the 1uF capacitor will charge to whatever voltage is present at the output on pin 5. When the button is pressed, the capacitor voltage will be applied to the input of the other timer which will reverse the state of both timers and toggle the relay, either on or off.

To follow it more closely, assume the output at pin 5 is +12 volts and the second output at pin 9 is zero volts. The 1uF cap will be charged to 12 volts. When the button is pressed, the cap will apply +12 to the inputs at pin 2 and 6 which will cause the output at pin 9 to go to zero, turning off the relay. When the button is released, the cap will discharge to zero, since the voltage at pin 5 is now zero. When the button is again pressed, the capacitor will apply zero to pins 2 and 6 causing the output at pin 9 to switch positive and engage the relay, and the cycle repeats.

The advantage of this circuit is the large hystersis range on the inputs. The button can be held closed indefinetly without upsetting the state of the outputs since the input voltage will be 1/2 the supply due to the equal value 100K resistors. The switching points are 1/3 and 2/3 of the supply so that a voltage of 50% has no effect. The circuit will also toggle very fast and needs no switch debouncing. One disadvantage is that it may turn on with the relay either engaged or disengaged. To solve that problem, you could use a resistor in series with one of the reset lines (4 or 10) and add a capacitor from the reset line to ground.

The 100 ohm resistor and 100uF capacitor serve to filter noise on the supply line if the circuit is used in a automotive application. They may not be necessary. The circuit may work well without those parts.

From : http://ourworld.compuserve.com/homepages/Bill_Bowden/