What are the uses for this variable resistor

Posted in Resistor
at 2019.12.16

What are the uses for this variable resistor?

  • this is used as a sensitivity regulator or feedback impedance level control.
  • it defines the frequency of the ne555 to set this pilot mini tesla coil / flyback.
  • changes the oscillation frequency of the timer. probably to allow to adjust it to a particular value
  • this variable resistor defines the oscillation frequency of the 555 timer chip.

When you move the cursor up, th and tl increase, which decreases the frequency of the timer circuit output. when the slider is lowered, th and tl decrease, which increases the frequency.

The charging time of the capacitor 1nf tiing is done via the potentiometer 18k plus the potentiometer 10k plus the potentiometer 50k.

The discharge time of the sync cap is controlled by the 50k plus the 10k-. As such, the frequency and the duty cycle are controlled by the 50 k potentiometer. work cycle means the ratio of the time during which the output is high to the moment when it is low.

This variable resistor controls the starting current charging the capacitor 1 nf to the supply voltage. when this voltage reaches a threshold defined in the ne555, the circuits of this chip discharge the capacitor 1 nf so that it can begin to recharge from the potential of the mass.

The net effect is to control the frequency of the pulse train appearing on pin 3 of the chip and therefore the frequency of the control input of the transformer. (See! It was not too difficult.)

It appears that the variable resistor is there to allow the adjustment of the ne555 oscillation frequency.

I imagine that a fixed resistor would allow the system to operate, but perhaps not at the correct frequency for optimal operation of the return transformer.

All electronic components, whose values ​​are not equal, from one device to another of the same type, may require that you need the variable resistor to get exactly the same performance or the same frequency of each circuit built from of this schematic diagram.

The 555 ic is used to generate the return transformer drive pulse (via the mosfet (irfp450) .

The 50k potentiometer adjusts the pulse rate that triggers the mosfet (irfp450), thus controlling the frequency of the return As a result, the voltage of the output hv of the transformer to fast return.

You can use a fixed resistor, but this will set the rate of the MOSFET and you will not be able to adjust the HV of the fast return Transform the transformer easily, ie change the value of the fixed resistor to do it Use a resistor from 0 to 50 000 ohms Variable resistors are often used when the tuning of the circuit.

The tolerances of the other resistors in your circuit may not be sufficient to fully determine the functionality of the circuit or component being controlled. show some variability, the resistance is most likely used to compensate for the error in the values ​​of the other or the controlled element.

I would suggest that you first designed the circuit with relatively high tolerance resistors.

Second, be sure to put the variable resistor you are referring to. third test of the circuit functionality to determine if the desired transfer function is generated. fourth, connect the circuit to what it controls.