Where there is heat, let us bring cooling: a fan will do the job, but unfortunately fans are usually noisy. In many cases there is no need for the fan to run continuously at full speed, and so it makes sense to control the fan speed in response to the temperature of the heatsink or device being cooled, switching the fan off entirely if it should f
Click here to download the full size of the above Circuit.
all to room temperature. The circuit shown here does this and even offers a little more. The low-cost KTY81-110 is used as the temperature sensor, in a negative-feedback arrangement with an operational amplifier. The temperature-dependent voltage at the non-inverting input to opamp IC1. A leads to a voltage variation at the output (pin 1) from 4 V at 30 °C to 4. 72 V at 60 °C. The second stage (IC1. D) converts this relatively small swing and inconvenient voltage offset into the range 8 V to 12 V suitable for the fan. The third operational amplifier works as a comparator. At room temperature its output sits at nearly 12 V and pulls the output of the second stage with it, switching transistor T1 off. If the temperature exceeds 35 °C the comparator switches; diode D1 blocks and the control circuit can operate as normal. The hysteresis of the comparator has been set so that the comparator state will only change again, turning off the fan, if the temperature falls below 30 °C. Capacitor C3 ensures that the fan is run at full voltage for about 0. 7 seconds immediately after switch-on, so that the motor will start reliably. The fourth opamp in the LM324, IC1. C, is used to create an over-temperature warning indicator. This is necessary in case the fan, even running at full speed, is not able to provide enough cooling, or, because of a fault, cannot reach full speed. This opamp is also configured as a comparator. If the sensor...
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: