Science Buddies: "Ask an Expert"

Ok here's the link to our project
https://www.sciencebuddies.org/science- ... ml#summary
We are in the middle of conducting our experiment. We have developed our artificial pancreas, however, the peristaltic pump is not turning off when the potentiometer is turned. We have bought all of the suggested products except the copper wire from the list, however, note that the speed is affected very, very slightly with the turn of the potentiometer. We have tried changing our alligator clip cables and have read over the experiment many times... Please post reply asap,we are conductng the project now. Project is due on January 1st 2015

Hello ashmistry,

Welcome to the forum. I'm sorry that you're having problems with your potentiometer and I will try to help.

Because your pump working, it appears that the connections in your circuit are OK.

I'm assuming that you are trying to turn the pump off with the potentiometer while the conductivity probe is in the neutral solution. Have you checked to make sure you prepared the neutral solution correctly? The solution should have a pH close to 7.

Another possibility is that your potentiometer is defective. You can check the potentiometer by connecting it to a multimeter set to measure resistance (ohms). If the potentiometer is working you should measure very high resistance (1 M-ohm) with the knob turned one way and very low resistance with the knob turned the other way.

I hope this helps. Please ask again if you have more questions.

A. Norman

norman40 wrote:Hello ashmistry,

Welcome to the forum. I'm sorry that you're having problems with your potentiometer and I will try to help.

Because your pump working, it appears that the connections in your circuit are OK.

I'm assuming that you are trying to turn the pump off with the potentiometer while the conductivity probe is in the neutral solution. Have you checked to make sure you prepared the neutral solution correctly? The solution should have a pH close to 7.

Another possibility is that your potentiometer is defective. You can check the potentiometer by connecting it to a multimeter set to measure resistance (ohms). If the potentiometer is working you should measure very high resistance (1 M-ohm) with the knob turned one way and very low resistance with the knob turned the other way.

A. Norman

Thanks norman40, but we found our problem just 20 seconds ago. Our white distilled vinegar wasn't acidic enough, so we tried pulp-free orange juice, ad it works like a charm. Thanks again man

I'm having the same problem, my solution is neutral, and the multimeter reads 0.6 one way and the 7.2 other way