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Sources for 3 Vdc
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mariush:
The potentiometer is like two resistors in series with values changing as you adjust it.
Configure the potentiometer at the minimum where your circuit still works, worst conditions, then measure resistance (between wiper and pin going to transistor).
This way you know you can add a resistor smaller than that value and still be able to use the pot. to adjust.
For example, let's say you have a 1000 ohm potentiometer and you measure the resistance at 200 ohm. This means you could add a 100 ohm or 150 ohm resistor in series, and lower the potentiometer to 100 ohm or 50 ohm to get same 200 ohm value at the end.
The benefit is if you somehow forget and move potentiometer all way to 0, you dontt damage transistor because it still has that 100-150 ohm value
fixit7:

--- Quote from: mariush on June 11, 2019, 12:39:38 pm ---The potentiometer is like two resistors in series with values changing as you adjust it.
Configure the potentiometer at the minimum where your circuit still works, worst conditions, then measure resistance (between wiper and pin going to transistor).
This way you know you can add a resistor smaller than that value and still be able to use the pot. to adjust.
For example, let's say you have a 1000 ohm potentiometer and you measure the resistance at 200 ohm. This means you could add a 100 ohm or 150 ohm resistor in series, and lower the potentiometer to 100 ohm or 50 ohm to get same 200 ohm value at the end.
The benefit is if you somehow forget and move potentiometer all way to 0, you dontt damage transistor because it still has that 100-150 ohm value

--- End quote ---

Ok, so with a 150 ohm  resistor in series with the pot, the resistance never gets below 150 ohms because that is the minimum resistance of that
part of circuit (assuming wire and component resistance at zero).



MarkF:

--- Quote from: Audioguru on June 09, 2019, 01:22:28 am ---This site is a nightmare to find posts by people. On all other sites I simply click on your profile.
I found your Laser Alarm Project but many of your photos were not posted here, instead you posted them over at Drop Box who deleted them.

--- End quote ---

It works the same on this forum.
   -Click on profile
   -Click on "Show Posts"

Audioguru:

--- Quote from: MarkF on June 12, 2019, 12:49:06 am ---
--- Quote from: Audioguru on June 09, 2019, 01:22:28 am ---This site is a nightmare to find posts by people. On all other sites I simply click on your profile.
I found your Laser Alarm Project but many of your photos were not posted here, instead you posted them over at Drop Box who deleted them.

--- End quote ---

It works the same on this forum.
   -Click on profile
   -Click on "Show Posts"

--- End quote ---
Thanks, Mark.
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