Science Buddies: "Ask an Expert"

I have redid the breadboard several time and the pump will still not turn on
I have tried every solution posted: Rotating the potentiates, changing the resistors, troubleshooting etc....
we know that the pump works because we tried several times to turn the pump on using batteries.
Are there any other ways to get the pump working.

Hi,
I am very sorry to hear that you are running into issues with the project.
Is there any way that you can post a picture of the breadboard that you have built please? We may be able to spot / identify the issues using the picture and give you better feedback.

Thanks!
Willey

I won't let me attach the image. It says that there is an error when I tried to add the image.Is there another way I can send it to you.

Hi,
Can you try attaching the picture as a pdf? (You can "print" the picture to a pdf file. Or insert it into MS Word)

Thanks!
Willey

I printed it to PDF
It said that the image is to large

Hi,
So sorry to hear that. Can you adjust the resolution of the picture down so that we can make the file size smaller?
Willey

Hi,
I am sorry about this but the image you posted is too small.
Can you do a picture of the breadboard (in color) and one of the overall circuit like the one you posted please?

(Sorry, I just thought of this: Please take a look at the following links for how to reduce picture size)
https://support.office.com/en-us/articl ... 4109eb9535

There are also a number of youtube instruction video on how to do this:
https://www.youtube.com/watch?v=hAMplAHLfSo

Thanks!
Willey

Hi - Being able to see a really clear and close up photo looking down at the breadboard will help Willey (and other Experts) troubleshoot with you. If you can take a few photos, you can email them to [email protected], and I'll make sure they get passed to Willey.

Amy
Science Buddies


[I've forwarded the photos you sent to Willey.]

Thank you
I hope he can find the issue

Hi,
Thank you for the pictures! They really helped. I looked at the circuit board and it looks to me that you have everything connected correctly. I do have a question on the battery pack though. In the picture, IMG_7370, I am seeing only 3 batteries. Can you confirm that when you have all 8 batteries installed that the pump still won't run please? (The circuit needs the full 12V (8 * 1.5V per battery) to operate).

Thanks!
Willey

Yes the pump does not work with all eight batteries. We just take one battery out when we are not using the circuit for safety purposes.
***If all the wiring is correct what should we do to get the pump to work when connected to the breadboard.***
Also, for the neutralized solution can we just use water.

Hmm... that's strange. Sorry, I forgot to ask one more question. There were two picture of the breadboard. The short one looks to have the correct circuit. The longer breadboard, IMG_7362, show the yellow wire going to 4d? (instead of 1d as shown in the short breadboard.) Would you happen to know why that change was made? Can you try moving that back to 1d?

In terms of next step, do you have access to a Digital multi-meter? we will need to take some measurement and see where the circuit may be giving us trouble. If that's not available, we may need to start switching out components.

We are using the short breadboard. We redid the breadboard several times, so we are going with the short breadboard.

Also, we do have access to a digital multi meter. What would be our next steps.

Hi,
Sorry for the delayed response.
With the Digital multi-meter, we are going to be taking measurements at different points of the circuit to see if we can identify what's wrong. Specifically, we will be using the circuit diagram at the "HELP" section as the basis of these tests. https://www.sciencebuddies.org/science- ... creas#help

To start, let's confirm that the 12V is getting to the circuit board.
1. Set you meter to read DC Voltage and apply the leads. The black lead should be attached to the BLUE rail, and Red lead should be attached to the Red Rail. If everything is working, you should have 12V on the meter.

2, The next place to measure is the voltage divider, Vout of Figure 14. Leaving the black lead in place, connect the lead to the resistor leg on 1C (or add a wire at 1D so that you can clip on to it.) This should read the Vout that you calculated using the equation. (It should be around 3V)

3. If this checks out, the next point to measure is the gate voltage at the transistor (after the conductivity sensor). Again, keeping the black lead at the same place, measure the voltage at row 7. (You can move the wire from 1D over to 7D if that makes getting the reading easier.) This is the VGS mentioned in the help file. When VGS is greater than Vth, then the pump should run. Please measure what this voltage and if it is less than Vth, please, adjust the potentiometer and see if you can bring up the voltage.

Hopefully, this should solve the problem. If not, please post again with your results and we can see what else may be going on.

Good Luck and Have a great Holiday!
Willey

I just have one more question. Do you think that the MOSFET has something to with our circuit not working.
Hope you also have a wonderful holiday.

Hi,
Yes, the MOSFET is most likely the problem if all of the voltages are as expected. (Out of all of the components on the board, it is the component most susceptible to damages.)

Willey

Then if the MOSFET is the problem what would we have to do to fix it.

It would have to be replaced with a new part.
(Unfortunately, there's nothing we can do to repair it)
Willey

When you say new part, do you mean a new MOSFET or something else.

Yes, new MOSFET.

We tested with the multi meter and tests one and two seem find, but step three there was no reading. We are going to test step three again when we make the solution.

Ok, good luck!

For this project, I was just wondering, where would we put this device in a human body. Also, I will follow up with my results.

Hi,
With our current technology, I don't think we will be putting this device inside a human body any time soon.
Here's the one of the latest article on its current development:
https://tcoyd.org/2018/02/the-artificia ... it-coming/

More than likely, at least in the initial phase, this will be an external device so that you can power the pump and resupply the insulin as needed.

Willey

Would this be a device that would, externally, be connected to our body and the pup tubes internally.

Also, in the article it said that the third component would be a device such as a phone to direct the insulin. What in our project directs insulin. Are we doing this manually?

In this project, the conductivity sensor is what controls the pump, please refer to Figure 4 in the background section. If the solution is conductive, the pump is turned on. If not, the pump is off.

Instead of just simple on/ off, the third component (Phone / Computer) mentioned in the article will allows you to do things like "pre-pump" the system before a meal or having the ability to predict what the blood sugar level might be after exercise, etc...

And yes, I am guessing people will wear this device on a belt with tubes connections to blood sensor and insulin injection site.

Willey

Thank you! I appreciate it.