DC Motor Speed Controller

This circuit takes advantage of the voltage drop across bridge rectifier diodes to produce a 5-position variable voltage supply to a DC fan or other small DC motor. It is not as efficient as a switch-mode circuit but it has the virtues of simplicity and no switching hash. The four full-wave bridges are connected so that each has two pairs of series diodes in parallel, giving a voltage drop of about 1.4V, depending on the load current.Circuit diagram:

DC Motor Speed Controller Circuit Diagram

The rotary switch should have "make before break" contacts which should be rated to take currents up to about an amp or so. For higher currents, higher rated bridge rectifiers and a suitably rugged rotary switch (or solenoids) will be required. If you want smaller voltage steps, you could use the commoned AC inputs on the bridge rectifiers to give intermediate steps on the speed switch.
Author: Stephen Butcher

Read More

Motor Bike Headlight Controller

This circuit automatically turns a motor cycles headlight on and off, independently of both the light and ignition switches, provided the battery is fully charged. The first stage uses the 22O resistor and ZD1 to hold transistor Q1 off while the motor is not running; it draws about 2mA. Once the battery voltage exceeds 7.0V during charging, Q1 begins to turn on. 

 
The last stage uses the 22O resistor and ZD2 to turn on transistor Q2, which pulls the base of Q1 down, switching it hard on. In conjunction with the Vbe drop of Q2, ZD2 will turn off Q2 at a battery voltage of about 6.7V. In practice, this means that the headlight will be on most of the time while the motor is running and charging the battery. Heatsinks are required for both transistors. The circuit can be mounted adjacent to the battery with a single lead going to the headlight power feed.

Motor Bike Headlight Controller Circuit Diagram:

Parts	Description
P1	5R - 3W
R1	220R -1W
R2	1R - 1W
R3	22R - 5W
R4	22R - 5W
Q1	BD139
Q2	MJ4502
D1	6.2V - 1WZener
D2	6.2V - 1WZener
B1	6.6V - 7.2V
F1	Fuse 15A
Lp1	DIP Beam 6V-25W Halogen

Read More

Automatic Water Pump Controller Circuit

Automatic water pump controller is a series of functions to control the Automatic Water Pump Controller Circuit in a reservoir or water storage. As the water level sensor made with a metal plate mounted on the reservoir or water tank, with a sensor in the short to create the top level and a detection sensor for detecting long again made the lower level and ground lines connected to the bottom of reservoirs or reservoir. The series of automatic water pump controller is designed with 2 inputs NOR by 4 pieces and relay that is activated by the transistor. Automatic water pump circuit requires +12 VDC voltage source and can be used to control the water pump is connected to AC power . Here is the complete series of pictures.

Series Automatic Water Pump Controller 

List Component Automatic Water Pump Controller 

R1 = 15K 

R2 = 15K 

R3 = 10K 

R4 = 1K 

D1 = LED 

D2 = 1N4148 

Q1 = BC337 

IC1 = 4001 

SW = SPDT Switches 

Relay RL1 = 12V 

The working principle series of automatic water pump controller above is. At the time the water level is below both sensors, the output IC1C (pin 10) will be LOW, and when the water began to touch the lower level sensor, the output IC1C (pin10) remains LOW until the water touches the sensor level above, then the output IC1C (pin 10) going HIGH and active relay through Q1 and turn on the water pump to meguras reservoir. At the muli down and water level sensors for water untouched MKA IC1C output (pin 10) remains HIGH until the new water untouched all sensor IC1C output (pin 10) LOW and water pump died.

The series of automatic water pump controller is equipped with SW1 which serves to reverse the logic of drains (the output of IC1C) and the concept of water supplied (output dri IC1D). When SW1 is connected to IC1D the water pump will turn on when the water does not touch all the sensors and will die when all the sensors tesentuh water. Automatic water pump controller can be used to fill or drain the water according to which mode is selected via SW1.

Read More