TL494 Working With a Crystal || Generate Perfect 50Hz Modified Square Waves
Introduction: TL494 Working With a Crystal || Generate Perfect 50Hz Modified Square Waves
Hello everyone! Thank you for stopping by this instructable.
This is a very exciting project where I have made this TL494 based modified square wave module that is controlled by a crystal oscillator for having super accurate output frequency of 50Hz and it also comes in with an adjustable deadtime control so that you can manually select the wave form that you want and all this without using any microcontroller!
I found this concept quite fascinating and thought of making a module which can generate the control signals for using it in a modified square wave inverter. This project used some very commonly used ICs which are easily available over your local hardware store as well as online.
So without any furthur delay lets get started!
Step 1: Gather Your Components
I will be designing this module almost completely based on SMD components to make the module small and compact but that should not stop anyone to try out this exact project using through hole components. The values of all the components remain exactly the same in both the versions.
So here is a list of all the components that you will be requiring for this build
1. IC TL494
2. IC 4060
3. IC 4017
4. IC LM358
5. 4.096Mhz crystal
6. 7805 voltage regulator
7. BC547 / 2N2904 or any other general purpose NPN transistor
8. 1 Mega ohm resistor
9. 100K resistors
10. 10K resistors
11. 1K resistor
12. 552
2.2Kresistors
13. 10K and 100K presets
14. 10K potentiometer-10 turn precision
15. 0.1uF and 0.01uF capacitors
16. 22pF capacitors
17. LED for power indication( optional)
18. Copper clad / veroboard
19. Male header pins
20. Soldering kit and accessories
All these components can either be used in the through hole or SMD form depending on how you want to make your circuit.
Step 2: The Idea
The idea of using the TL494 with a crystal oscillator came to my mind when I was going through the datasheet of the IC, which mentioned that the IC can be used in a master slave configuration such that the ICs can be cascaded together in such a way that one IC can control the operating frequency of the other ICs connected to it. I found tis very fascinating and began investigating more.
Basically the TL494 is a very popular PWM control chip used in a variety of switching applications and power supply circuits due to some of its useful features like :
* Having two error amplifiers which can be used as a feedback mechanism in controlling the output voltage or limiting the current
* Flip flop based output so that we have two alternatively switching outputs
* external R and C component connections to determine the output frequency based on the RC time constant
* Internal 5 V reference that can be useful for the error amplifiers
* Adjustable dead time control between the output pulses
* A good range of operating voltage
Phew, that was a lot and to get more information about this IC, I have attached the datasheet in this step for your reference.
Now coming to the signal generation, i have successfully generated a stable 50Hz and a 1Khz signal using the 4.096Mhz crystal using the IC 4060 which is a binary counter/ divider and a decade counter IC. If you are interested in how that circuit works, then more details are there in one of my previous projects the link to which is - https://www.instructables.com/Generate-Stable-50Hz...
The idea here is to use the binary divider ( IC4060) to generate 1Khz signal rom the crystal and then divide it by 10 using the decade counter IC 4017, in our case to get stable 100Hz which can then be fed to TL494 to generate two alternatively switching 50Hz signal at the output as from the datasheet it is clear that TL494 can accept sawtooth waves as input on pin CT when used as a slave. The deadtime can be controlled by applying a voltage between 0.7 to 3.3 volts which can change the deadtime from 3% all the way upto 100%. This can easily be controlled via a potentiometer. I have attached the snippets of those exact concepts in this step.
Step 3: The Contradiction... and the Solution
Well with the concepts discussed in the previous section I was all set to make this circuit but while testing the circuit on breadboard I faced a peculiar problem. 552