In this circuit we demonstrate how to use SCRs to control low-voltage pulsating DC to operate homemade LED light panels. While in this circuit I use the Arduino, the concepts should work with any number of micro-controllers using either hardware interrupts or polling. We must use pulsating DC or the SCR won`t operate properly. See Basic SCRs/Triac
Click here to download the full size of the above Circuit.
s. In the main circuit diagram above transformer T1, D1, and D3 produce a positive going pulsating DC with a peak voltage of about 18 volts and a frequency of 120 Hertz. Diode D2 blocks the filtering effect of capacitor C2, which with U2 supplies positive five volts for the microcontroller. See Basic AC Rectification and Filtering The 4N25 opto-coupler provides a narrow 120 Hertz pulse at zero and 180 degrees of the sine wave. This pulse is fed to digital pin 2 (Dp2) of the controller to trigger an interrupt when the sine wave passes zero and 180 degrees. (There`s 360 degrees in a sine wave. ) See 4N25 Opto-Coupler (PDF file) CdS photocell R6 and R3 form a voltage divider. As light intensity increases the resistance of R6 decreases causing the voltage to rise at the junction of R3, R6, and analog to digital converter pin Ad0 on the controller. (R3 can be a 10k resistor, which is what I used. ) When read by the program this 10-bit AD converter will produce a value between 0 and 1023. This value is used in a delay routine to determines the firing point of the SCR. The longer the delay, the less power to the LED strings and less light output. See Using a CdS Photocells When the power on switch is pressed at Dp4 a 100 uSec. positive-going pulse is sent to the H11C6 opto-coupler through a 470 ohm resistor. This in turn fires the SCR at the desired time during the delay time 120 times per second. The H11C6 contains a LED light...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
characters left: