lm393 change potentiometer???

we have purchased an arduino compatible mic board,

it has a small multi turn pot to control the sensativity, is there a way of swappintg this pot to a standard 1 turn pot?

we have tried using a 10k,20k, and a 50kohm pot but cant get get the accuracy needed?
is there an easier way of doing this?

The reason is that we need access to this adjuster on the out side of its encolsure

many thanks

104 is stamped on top. A ten with four zeroes. 100k.
AFAIK this pot sets the comparator threshold for the digital output.
Leo..

Hi thank you, we have just tried placing a 100K pot but the adjustment is off to full within a fraction of a turn. is there a way of spreading the adjustment accross the entire sweep of the pot?

So now you know why it was a ten turn pot, eh?

Of course there is. :grinning: Use a 10k pot in series with a 100k (91k?) resistor and you have it solved.

Hi,
Have you identified the proper pinouts on the tenturn pot?
Have you found the pin for the wiper, and yes you are now finding why its a 10 turn pot.

Tom..... :slight_smile:

this is proving harder than it should be. i was thinking the orig multi turn pot would be the same pinout as a standard pot. however a multimeter is showing 5volt going into one of the outside pins and also the center pin. not sure where the other pin goes but it doesnt go directly to earth as i thought it should?

maybe it would be easier finding a multiturn pot that has a larger adjustment dial?

thanks for all your help

Hi,
Check the pot you took out for the pin configurstion, not the PCB if it is difficult to trace.

Tom… :slight_smile:

Hi, i thought that we had this sorted, we decided to use a MCP4151 digital pot to control the comparator threshold, this all works very well and we can now change the resistance up and down via a couple of buttons. however there seems to be noise on the lead as you can see the detection LED flash dimly. We have also wired in a LED on our board that fades up and down when powerd. When it is at its brightest it also activates the detection LED. this obviously is not helping and gives false readings.

Whats the chances that any one on here as changed the pot to a digital one in the past? Or can kindly point me in a direction to look at??

Many thanks once again

Spriggsy

Can you post a schematic? (hand drawn is fine)

And also describe under what conditions you see incorrect behavior. Does it only happen when it’s right at the threshold, or all the time?

Hi thanks for the offer to help, it turned out to be a damaged A0 pin on the arduino. didnt realise it was this as i was getting some readings on it. swapped to A1 and it works perfectly. thanks again

Spriggsy