N-channel MOSFET

[amalsafiia]

I am a seventh grader that has a science fair in about two weeks. The project I chose was "Dealing with Diabetes: The Road to Developing an Artificial Pancreas". If you look in the materials box it says you need an N-channel MOSFET. When you open the link to Jameco it says it won't ship until April. I do not have that kind of time. So does it have to be the same MOSFET with the same number of volts and everything? Please help. And thank you so so much for taking your time to read the post and maybe reply. I really appreciate it. A lot. *hope I provided enough information for you to answer my question*
Amal

[SciB]

Hi Amal,

The MOSFET is a key part of the circuit and I don't know if there is anything you can replace it with. You should call Jameco and talk to someone in tech support and ask them if there is a component you could use in its place.

If you can't get the MOSFET from Jameco, do an online search and try to find another supplier.

You could also post your question on the Scibuddies Physical Sciences forum because the experts there may be more knowledgeable about electronics than life sciences people.

Let us know how you make out.

Sybee

[amalsafiia]

thank you so much

[SciB]

You are welcome!

Please let us know what you find out about substituting a different component for the MOSFET or finding another supplier. Your feedback is important to us! Some other student may have the same problem in the future and having a Plan B is always a good idea.

Thanks,

Sybee

[amalsafiia]

No thank you. I took note of your advice of checking other online sources and found one from Amazon and the best part was that it came with ten of them. I heard that the MOSFET is very sensitive so I was really happy.!
Amal Safiia

[amalsafiia]

Hello, my name is Amal I am in 7th grade and I and my friend are working on a project on your website called " dealing with diabetes the road to developing an artificial pancreas" is it ok if someone would clarify how the pump works. I understand that it consists of a voltage divider which are the two resistors and a MOSFET. But I still don't get it. Thank you so much for taking your time to read this. I appreciate it.
PS.Can I title the project dealing with diabetes? wanted to ask permission because it's not my idea.
Amal

Moderator Note: I merged this post with your other posts on this topic. Please keep your posts together so the expert who is helping you will see that you have follow-up questions. Thank you!

[amalsafiia]

Also, I have the question if that's okay. I am working on a project on your website called " dealing with diabetes the road to developing an artificial pancreas" is it ok if someone would clarify how the pump works. I understand that it consists of a voltage divider which are the two resistors and a MOSFET. But I still don't get it. Thank you so much for taking your time to read this. I appreciate it.
PS.Can I title the project dealing with diabetes? wanted to ask permission because it's not my idea.
Amal

[SciB]

Hi Amal,

Glad you found the MOSFETs from another supplier, and now you have extra if any break or are defective.

I don't know if you saw the circuit description in the project Help section but here's the link: https://www.sciencebuddies.org/science- ... creas#help

The voltage divider with R1 and R2 senses the resistance of the solution and regulates the V-out which goes to the MOSFET. The MOSFET is a sort of transistor that acts as a switch depending on the input voltage. When the solution is just water and therefore has very high resistance then no V goes to the gate and no current flows to turn on the pump. When the solution is made conductive by adding vinegar, there is a V that goes to the MOSFET gate and if it is above the threshold the circuit allows current to flow and the pump to operate to neutralize the acidity with sodium bicarbonate.

I hope this helps. If you have more questions post again. Be careful and double-check your connections on the breadboard. It is easy to make a wrong connection or to have one that is loose, so follow the instructions to the letter.

Good luck!

Sybee

[SciB]

Oh, i just remembered i forgot to answer your question about the project title. I don't see any reason why you couldn't use the title given in the project, but it would be more fun and personal for you to name it something that YOU thought up. Think about it. You have time to come up with your own title.

Sybee

[amalsafiia]

Hello my name is Amal Safiia I am in 7th grade and I am working on a science fair project on your website called On the road to developing an artificial pancreas. I am having some troubleshooting with the artificial pancreas me and my partner built.
When we got our potentiometers they did not come with individually labeled bags for each potentiometer so now we have no clue which potentiometer is which and where to put them. We only have one week until we present and we need help. Please. Thank you for taking the time to read this question and maybe even answer it. It is greatly appreciated.
amal

Moderator note: Please keep all your questions on this topic together - that way the expert who has been helping you will see that you have a follow-up question. Thank you.

[SciB]

Hi Amal,
Did you buy the pots from Jameco? Most electronic components have a label that indicates their type. The artificial pancreas model uses 3 pots. They should have markings that indicate their maximum resistance. One should be 1 million ohms which is abbreviated 1 MO except that the O is actually the Greek letter for omega. The second pot is 100 kO which stands for 100,000 ohms. The third pot is 10 kO or 10,000 ohms.

I hope this helps. Post back and let us know.

Sybee

[bfinio]

Hi Amal/Sybee,

Unfortunately the potentiometers from Jameco do not have labels printed on them, so if you get them mixed up or they don't come in separate bags in the initial order, they are impossible to tell apart just by looking at them. Amal, if you have access to a multimeter, you can measure the resistance of each one by measuring the resistance between the outer two pins. We have a multimeter tutorial if you need help:

https://www.sciencebuddies.org/science- ... resistance

Once you figure out which is which, I'd recommend writing on them with a fine-tipped permanent marker so you can tell them apart.

-Ben

PS - Sybee, I don't usually check the life sciences forums, so thanks for recommending that people post circuit questions in the physical sciences forums.

[bfinio]

Oops - I need to correct my previous post. I just checked my potentiometers and it looks like they do have markings on them, indicating powers of 10. For example, the 10 kilo-ohm potentiometer has R103 printed on it - the 103 means 10^3. 10^3 is only 1,000, not 10,000, so multiply that by an extra factor of 10 to get the resistance value. So (assuming you bought the potentiometers from Jameco) you should see

10 kilo-ohm : R103
100 kilo-ohm: R104
1 mega-ohm: R105

As I described in the previous post though, using a multimeter is still a good way to confirm if you aren't sure.

[SciB]

Hi Ben and Amal,

Ben, I just saw your latest post where you say that there are labels on the Jameco pots.

Amal, check the pots for the codes and let us know if you see them. If you do then you don't have to use a multimeter as I suggested below. But, as Ben says, it would be nice to have one just to verify that the resistance is correct. They are useful gadgets to have. You can measure the voltage of batteries to see how good they are. You can check for open circuits using the ohms scales. You can check for 110 volts AC in your home outlets. They are used also to check auto batteries, fuses and circuits.

Post again when you have figured out the pots to let us know.

Sybee



Hi Ben and thanks for the helpful info about the lack of labels. I know something about circuits but not always enough, so I am glad that you saw my post.

Hi Amal,

Ben has just shot down my method for distinguishing the potentiometers ('pots') by informing us that the components have NO labels. But, as he suggests, there is a way to identify which is which. Do you have a multimeter or know a friend or family member who has one? If you don't know what I am talking about, a multimeter is an electronic gizmo that can measure voltage, current and resistance. That's why it is called a MULTI-meter.

What you need is the ohms scale, so you can measure the resistance of each of the pots. I told you what the ohm values should be according to the information in the project materials section. Once you have a multimeter, set the ohms scale to maximum and read the resistance across each of the pots. You will have to turn the control on the pot to max resistance to get the correct value.

Hope this works! Let us know, and as Ben suggested, make a label for each pot so you don't get them mixed up.

Sybee

[bfinio]

Hi Sybee - one minor note - since these are three-pin potentiometers, you can always measure the maximum resistance by measuring between the two outer pins. The knob position doesn't affect this - it changes the resistance between the MIDDLE pin and either of the two outer pins. Your method would be correct for a "variable resistor" which only has two pins. See the second set of diagrams on this page, that should make it clear:

https://learn.sparkfun.com/tutorials/ho ... ols-part-1