PWM Generator is an important piece of equipment used to control a wide range of devices like DC motors, Thermo-electric coolers, LEDs etc. It is widely used in control applications at industrial level as well as domestic level. Here we have demonstrated the construction of a calibrated PWM Generator which provides accurate pulse widths on a frequency range from 100 KHz to 1 MHz with a constant resolution of 7 bits. The highlight of the system is that the user can independently tune Ton and Toff, and the error in the output time period is 1 part in 1000. Towards the end, the device is employed in a a variety of applications such as varying intensity of LEDs, speed of DC motors, and interfacing Peltier Coolers to regulate the temperature of electronic systems. Here are some pictures of the initial stages and the debugging stages.
Development Stage
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| Hardware Ready to be Tested |
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Peltier Cooler The device comprises of a heat sink (black), a thick piece of Aluminium and between them lies the Peltier Cooler. It consists of pn junctions doped with Bismuth Telluride. When a DC current is passed through the Peltier device in 1 direction ; one plate gets heated up and the other one cools down. The difference in temperature is controlled by the current flowing through the device. I used an H Bridge to switch the direction of current either ways, so that I keep both the plates either hot or cold. During the final assembly I deliberately passed current through the Peltier Device in such a way that the system coupled with the Al uminium plate cools down gradually. (Now I cant put up pictures of the Peltier device coupled with the system to be cooled down because this project was created in LASTEC, DRDO and there are confidentiality issues associated with it). |
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