What do the pots do in this circuit?

  • Thread starter godman
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In summary: From what I can tell from the wikipedia article, the comparator switches when the voltage at threshold (pin 2) is greater than the voltage at control (pin 3). The voltage at control is set at 2/3 Vs, so if Vs is 5, what difference does it make if the voltage at pin 2 is set at 1V or 2V by the pot? The comparator only switches at 3.3V so what use does being able to vary the voltage from 0-3.3V have if the 555 will be in the same state in that entire range?
  • #1
godman
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This is a circuit diagram of a 4-step sequencer connected to an atari punk console. What I want to know is what those pots connected between the 4017 chip and the diodes do. I know they control what voltage appears at the terminal connected to pin 2 of the 556, but that pin 2 is the threshold pin that only responds to two different voltage levels, high and low, so surely the pots do nothing and one only really needs the switches?

Here is the schematic: http://note.monoanimal.com/images/apccircuit_2.jpg

Sorry for the quality.
 
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  • #2
I think you are right. (I am thinking only in terms of ' output from 4017 being selectively applied to trigger pin of 556' I don't know what the rest of the circuit do)
 
  • #3
The pots set the voltage level for pin 2 of the 556. The diode drop is more or less constant so you can adjust what two voltages are sent to the 556 by adjusting the voltage on the anodes of the diodes with the pots. They are an important part of the circuit if you need to do any kind of level shifting between the 4017 and the 556.
 
  • #4
carlgrace said:
The pots set the voltage level for pin 2 of the 556. The diode drop is more or less constant so you can adjust what two voltages are sent to the 556 by adjusting the voltage on the anodes of the diodes with the pots. They are an important part of the circuit if you need to do any kind of level shifting between the 4017 and the 556.

I don't understand how the pots have any more affect that the switches do, unless the pots allow slightly greater control as to how fast you want the comparator to trigger. Does that sound right?
 
  • #5
godman said:
I don't understand how the pots have any more affect that the switches do, unless the pots allow slightly greater control as to how fast you want the comparator to trigger. Does that sound right?

The switches don't adjust the voltage levels, they just allow whatever it happens to be to go through. The pots allow you to adjust the voltage level (e.g. 1V or 4V or whatever).

So, the pots allow you to set the threshold where you want the comparator to trigger.
 
  • #6
carlgrace said:
The switches don't adjust the voltage levels, they just allow whatever it happens to be to go through. The pots allow you to adjust the voltage level (e.g. 1V or 4V or whatever).

So, the pots allow you to set the threshold where you want the comparator to trigger.

From what I can tell from the wikipedia article, the comparator switches when the voltage at threshold (pin 2) is greater than the voltage at control (pin 3). The voltage at control is set at 2/3 Vs, so if Vs is 5, what difference does it make if the voltage at pin 2 is set at 1V or 2V by the pot? The comparator only switches at 3.3V so what use does being able to vary the voltage from 0-3.3V have if the 555 will be in the same state in that entire range?
 
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Related to What do the pots do in this circuit?

1. What are pots in a circuit?

Pots, short for potentiometers, are adjustable electronic components that are used to control the flow of electric current in a circuit. They consist of a resistive element and a movable contact or wiper that can be adjusted to change the resistance and therefore the current in the circuit.

2. How do pots work in a circuit?

Pots work by varying the resistance in a circuit. When the wiper is moved, it changes the amount of resistive material that the current has to pass through, thus changing the overall resistance and current flow. This allows for precise control of the circuit's output.

3. What are the different types of pots used in circuits?

There are several types of pots used in circuits, including rotary pots, slide pots, and trim pots. Rotary pots have a circular control knob and are commonly used for volume or tone control. Slide pots have a linear slider and are often used for faders in audio equipment. Trim pots are small and usually used for fine-tuning circuits.

4. How do pots affect the function of a circuit?

Pots can have a significant impact on the function of a circuit. By changing the resistance and current flow, pots can alter the output of a circuit, such as the volume of a speaker or the brightness of a light. They can also be used to adjust the frequency response or filter certain frequencies in a circuit.

5. Can pots be replaced or substituted in a circuit?

Yes, pots can be replaced or substituted in a circuit. However, it is important to use a pot with the same resistance and power rating as the original one. Using a pot with a different resistance may affect the circuit's function, and using one with a lower power rating can cause it to overheat and fail.

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