ptr 08100wvd module, trimmer question

[styl3r]

I have already built this mod successfully but want to use a different trimmer (potentiometer) the original was  220 ohm the closest i can get in the type i want is 200 ohm just wondered how much this would impact the voltage output. i know how to work standard resistance (VIR) but not variable I.ve attached the original circuit diagram.....looks familiar.
Cheers guys
Styl3r
p.s. or if anyone has any links to finger single turn pots 10mm X 10mm needs to be small these are the ones i've found sorry for poor quality had to resize


 

[Breaktru]

That diagram was my first. I used the 220 ohm pot because I had a bag of them. I needed a total of 420 ohms, hence the 200 + 220.
If you look at the resistance table in the spec sheet, you will see what output voltage can be expected. Also the updated diagram is here:
http://breaktru.com/smf/index.php/topic,170.msg318.html#msg318

With the 420 ohms, Full Pot + fixed resistor you can expect approximately 3.4v output
With the Pot Zero'ed + fixed resistor (220) you can expect approximately 6.1v output
With the Pot Zero'ed + fixed resistor (240) you can expect approximately 5.5v output

Voltage output is approximate and depends on the actual resistance readings. Don't expect your 220 ohm, 20% resistor to read 220 ohm. I now try to buy 1% tolerance resistors where available or 5%. This also pertains to Potentiometers.

[styl3r]

Hi Dave thanks for the reply so if i used a 200 ohm pot and 200 ohm resistor i would acheive approx 3.5-6.5 ?  table only goes upto 0.241=5.5 looked on the Ti data sheet and it says the module output is max 5.5v but yet i have made one that will output over 6v as per your original schematic.
cheers
Kev

[nico]

I'll second that breaktru...always verify the resistance. I picked up a few of these 470 ohm pots...they are excellent...nice precision and feel and sealed with an o-ring...just have to add a 390 ohm resistor in parallel for 200ohm...by themselves they dial in at around 400 ohm...not the rated 470...still within the 20% tolerance rating...kinda big though but doable. http://www.mouser.com/Search/ProductDetail.aspx?R=P16NP471MAB15virtualkey61330000virtualkey72-P16NP471MAB15

and by the way... do not try to take the knob off....I thought it was on a stem...but its not...its a very integral part of the pot!




Yeah its about time I signed up...I'm slow getting around!  Geez..you'll let anyone in here! 

Great forum Breaktru...thanks for all your work and help in the mod world...especially with the 1869 digital pots which I have built few and are working fine. 

[Breaktru]

Welcome nico, glad to have you aboard.