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[SOLVED] how to use trimpot ?

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andihong

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i am new here using Trimpot ( three - leg trimmer potensiometer )..

here the picture i got,
Trimpot.png

here my example, if port A i give Voltage, and port B is the output,

is the wiper connected to ground ?
 

bigdogguru

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here my example, if port A i give Voltage, and port B is the output,

is the wiper connected to ground ?

Although the configuration depends on your application, typically you would apply the voltage you wish to attenuate across A and B, for example, V+ on A, GND on B and then taking the resulting voltage (output) from the wiper (C). Such a configuration would yield a voltage range on the wiper (C) from V+ to GND depending on the trimpot adjustment.

What is your specific application?

BigDog
 

andihong

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Although the configuration depends on your application, typically you would apply the voltage you wish to attenuate across A and B, for example, V+ on A, GND on B and then taking the resulting voltage (output) from the wiper (C). Such a configuration would yield a voltage range on the wiper (C) from V+ to GND depending on the trimpot adjustment.

What is your specific application?

BigDog

for example, i give V+ 12V on A and i want to get 10V output from trimpot,
i can use V+ on port A and output on port B because if i using ground on Port B and wiper as output, it became 6V ? right ?

thanks for answering..
 

bigdogguru

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for example, i give V+ 12V on A and i want to get 10V output from trimpot,
i can use V+ on port A and output on port B because if i using ground on Port B and wiper as output, it became 6V ? right ?

Answer this question:

If you connect V+ on A and GND on wiper (C), what is the result of adjusting the trimpot to its two extreme positions?

Also, what is the intended purpose of the resulting voltage output?

BigDog
 

Vbase

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i am new here using Trimpot ( three - leg trimmer potensiometer )..

here the picture i got,
View attachment 117574

here my example, if port A i give Voltage, and port B is the output,

is the wiper connected to ground ?
Connect A to 12V and B to ground. The output is the Wiper. Connect output to the DAC. Turn the pot until you get 10V at the output.
 
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andihong

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Answer this question:

If you connect V+ on A and GND on wiper (C), what is the result of adjusting the trimpot to its two extreme positions?

Also, what is the intended purpose of the resulting voltage output?

BigDog

i haven't try it, but i want to get 10V for input DAC0808 circuit.

Connect A to 12V and B to ground. The output is the Wiper. Connect output to the DAC. Turn the pot until you get 10V at the output.

thank you for the advice, you know i am using it for DAC..

such a great person, thank you.
 

bigdogguru

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@andihong,


I clearly answered the initial question back on post #2.

Utilizing this method to generate a VREF while not ideal, can be used in a pinch to test your circuit.

However, you certainly would NOT use such a method to power one or more devices, you need to employ a regulated power source.


BigDog
 

andihong

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@andihong,

Utilizing this method to generate a VREF while not ideal, can be used in a pinch to test your circuit.

However, you certainly would NOT use such a method to power one or more devices, you need to employ a regulated power source.


BigDog

I just need a 10V input source from 12V, so i need to trimmed it. It is have a side effect?

And if i want to change 5000k ohm resistor to trimpot, how big the trimpot should i buy? Still 5000k or above?
 

bigdogguru

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As I indicated in my previous reply, for many applications, utilizing a resistor to generate a VREF for a DAC or ADC is less than ideal. Many types of resistors are inherently noisy and influenced by temperature changes, therefore not an ideal voltage reference, you would be better off with a precision zener diode or one of the many voltage reference devices available. However, depending on your specific application, a trimpot may suffice or at least it would allow you to test your design. You want to minimize current flow, so a 10KΩ or larger would be preferable, the current requirements for a VREF on a DAC or ADC is typically very low, in the uA or nA range.

As I'm not familiar with the specific design requirements, I can only offer general advice.
 

hobbyckts

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If the voltage is the sake for providing as an input. You could follow the same method of employing trimpot.

or else if you want to provide 12 v constantly then use a voltage divider circuit which provides the voltage of required level.
 

SunnySkyguy

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Resistor dividers have been used for a Vref from regulated power supplies since electronics began.

They often include an RF cap to block thermal noise in the resistor when used with comparators, so that the slew rate on power up is not too slow. There is an implied tradeoff here.

If perfect step response is mandatory on power on a cap. divider is also used in parallel, with the same ratios of impedance or inverse capacitance.

The down side is the % Vdc tolerance is only as accurate as the higher regulator plus the sum of the resistor tolerance. As the number of significant figures of accuracy, so does the cost increase by orders of magnitude.


Generally bandgap reference diodes are integrated with OpAmps and laser trimmed R's for the most economical Vref using a 10 or 15 mA vref chip, some are fixed and others called adjustable "Zeners" in reference to the man by the same name who invented or discovered the zener effect as the breakdown effect in semi's.

I always revered those whose discoveries are called by their name. Some day I would like to be remembered like this with my diode equation for ESR=Pmax/Imax (based on saturation of efficient diode ) as a rule of thumb not a result of math per se... Fat chance, it's probably been already documented.
 
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